This page shows what was measured, who it was measured in, and what that does not settle.
What Diltiazem does in the body
Diltiazem blocks that channel.
Muscle cells in artery walls need calcium flowing in before they can squeeze, and the electrical relay between the top and bottom chambers of the heart uses the same kind of calcium channel to pass its signal. Arteries widen, including the coronary arteries feeding the heart itself, so chest pain from narrowing or spasm eases. At the same time the electrical relay slows, which is why the pulse comes down and why the drug can control a racing, irregular heartbeat.
Why people take it. Chest pain, high blood pressure and some fast or irregular heart rhythms.
What happened in people
After a heart attack, benefit appeared only in people without lung congestion. Those with congestion had more heart problems.
✓ Reviewed first-read answer
Where this came from
A person wrote this and a reviewer approved it against this exact record. It carries no effect size.
A reviewer approved this against this record. The reviewed-claim record carrying the exact population and effect size does not exist yet.
No source is stored against this line.
The limit that matters most
For stable chest pain, it improves exercise time but has not been shown to prevent heart attacks.
Where it acts
Atrioventricular node and coronary vascular smooth muscle — the benzothiazepine binding site on the L-type calcium channel
Kind of result
Living longer, or avoiding a major event
Supervision
RNAWiki has not recorded a supervision or regulatory status for this substance.
Where each sentence above came from
A person wrote this explanation into the record, with the studies named in the path below.
A reviewer approved this sentence against this exact record and its sources.
The limit a reviewer approved as the one that matters most here.
The four opening statements run to 115 words.
Words this page uses
Four words worth knowing first
Chosen from what this page shows, with each one explained before the word it depends on.
Comparator
A comparator is whatever the treatment was measured against.
A picture of it, and where the picture fails
It is like the other runner in a race.
Where that stops being true. A race has one winner. A study can show both arms improved.
What people get wrong. Results are read without asking what the other group got. Beating nothing is not beating a treatment.
The control condition against which the experimental intervention is assessed.
Randomisation
Randomisation means chance decides who gets which treatment.
A picture of it, and where the picture fails
It is like a coin toss deciding the groups.
Where that stops being true. A coin toss is fair once. Fairness here comes from doing it for everyone.
What people get wrong. It is thought to make groups identical. It makes them similar on average, including on things nobody measured.
Allocation of participants to arms by a chance process, so that unmeasured factors are balanced in expectation.
Absolute difference
An absolute difference is how many more people in a hundred were affected.
A picture of it, and where the picture fails
It is like counting heads in two rooms of a hundred.
Where that stops being true. Heads are easy to count. Study results carry a margin of error too.
What people get wrong. It is confused with a percentage change, which can look far larger.
The arithmetic difference in event rates between arms.
Confidence interval
A confidence interval is the range the true answer is likely to sit in.
A picture of it, and where the picture fails
It is like a weather forecast giving a range rather than one number.
Where that stops being true. A forecast range covers tomorrow. This one covers what the study could resolve.
What people get wrong. The middle number is read as the answer. A range crossing zero means no change is still possible.
An interval estimate that would contain the true parameter in a stated proportion of repeated studies.
What happened in people◇Read from sources, not yet reviewed
What happened in people
Each card is one study: the exact question it asked, who was in it, and whether it showed what it set out to show.
Total mortality and first recurrent cardiac event after myocardial infarction
Total mortality 167 against 166, nearly identical; first recurrent cardiac events HR 0.90 (95% CI 0.74 to 1.08); interaction with pulmonary congestion p=0.0042
Repeated elsewhere
Unreplicated
What this does not prove. A study that did not show an effect does not show that no effect exists anywhere.
The limits of this study, and where it came from
Main limit. In the 490 patients with pulmonary congestion the hazard ratio was 1.41 (95% CI 1.01 to 1.96) — a 41% increase in cardiac events. That subgroup is now a contraindication on the label.
How far it carries. This study is recorded from the curated record, not from the registry match.
Form and route. Immediate-release tablet, several extended-release capsule and tablet formats, and an intravenous bolus and infusion
Interval reported. 95% CI 0
Written into the record, not signed off as a reviewed claim.
16.6 against 16.2 events per 1,000 patient-years; relative risk 1.00 (95% CI 0.87 to 1.15), p=0.97
Repeated elsewhere
Unreplicated
What this does not prove. Meeting one endpoint in one population does not carry to other goals or other people.
The limits of this study, and where it came from
Main limit. Open-label design with blinded endpoint adjudication. Systolic pressure fell 3 mmHg less on diltiazem (p<0.001), so equal outcomes were achieved at unequal blood pressure — which can be read as a drug advantage or as a chance finding, and the trial cannot distinguish them.
How far it carries. This study is recorded from the curated record, not from the registry match.
Form and route. Immediate-release tablet, several extended-release capsule and tablet formats, and an intravenous bolus and infusion
Interval reported. 95% CI 0
Written into the record, not signed off as a reviewed claim.
Composite of bleeding-related hospitalisation and death with recent evidence of bleeding, diltiazem against metoprolol in users of apixaban or rivaroxaban
✓ The study showed what it set out to show
Who was studied
Ray et al. Medicare cohort (JAMA 2024;331:1565-1575)
How many people
204155
Study design
Retrospective cohort with overlap weighting, not randomised
Compared against
Not recorded for this study
Kind of result
Living longer, or avoiding a major event
What was found
Rate difference 10.6 per 1,000 person-years (95% CI 7.0 to 14.2); hazard ratio 1.21 (95% CI 1.13 to 1.29), with a dose gradient above and below 120 mg daily
Repeated elsewhere
Unreplicated
What this does not prove. Meeting one endpoint in one population does not carry to other goals or other people.
The limits of this study, and where it came from
Main limit. Observational. Channelling by indication is possible even between two rate-control drugs, and the median follow-up was 120 days, which is short relative to the anticoagulation itself.
How far it carries. This study is recorded from the curated record, not from the registry match.
Form and route. Immediate-release tablet, several extended-release capsule and tablet formats, and an intravenous bolus and infusion
Interval reported. 95% CI 7
Written into the record, not signed off as a reviewed claim.
RNAWiki holds 3 written-up human studies for this substance, each with the question it asked.
How we know it
Each card names the study, the number of people and what the study set out to measure.
What this does not prove
These summaries were written by a person and have not been signed off as reviewed claims.
Why it matters
A study that failed is as informative as one that worked, and both are here.
What we still do not know
No reviewed claim exists, so no exact population, effect size or interval is published yet.
What it changes in the body◇Read from sources, not yet reviewed
The path through the body
From what a person takes to what changes. A solid line is a step measured in people. A dashed line is a step nobody has measured that way.
Where a source records it acting
Blood and vessels: Produces its antihypertensive effect primarily by relaxation of vascular smooth muscle and the resultant decrease in peripheral vascular resistance
US prescribing information · 0089fc7a-a7aa-4873-b699-39a1b21616ca · read 2026-08-27
Heart: Produces increases in exercise tolerance, probably due to its ability to reduce myocardial oxygen demand via reductions in heart rate and systemic blood pressure
US prescribing information · 0089fc7a-a7aa-4873-b699-39a1b21616ca · read 2026-08-27
Start
Diltiazem
What a person takes: Immediate-release tablet, several extended-release capsule and tablet formats, and an intravenous bolus and infusion.
The measurement behind this step
The oral forms are not interchangeable: the many extended-release products differ in release profile and are approved separately, which is why 177 distinct products are listed in the pricing survey. The intravenous route exists for one job the oral route cannot do quickly enough — bringing down a fast ventricular rate in atrial fibrillation or flutter, and converting paroxysmal supraventricular tachycardia.
What it acts on
A different door on the same channel
The calcium channel this drug blocks has several separate binding pockets. Diltiazem uses one of its own, which is why it behaves differently from amlodipine even though both are called calcium channel blockers.
╌╌Described, with no measurement named. No measurement is named for this step, so it is drawn as an unconfirmed link.
The measurement behind this step
Diltiazem binds the benzothiazepine site on the alpha-1C subunit of Cav1.2, distinct from the dihydropyridine site used by amlodipine and the phenylalkylamine site used by verapamil. Block is use-dependent, so tissue that is depolarising frequently is blocked more than tissue that is not.
With calcium entry blocked, the muscle wrapped around arteries relaxes. The coronary arteries feeding the heart widen along with the rest.
╌╌Described, with no measurement named. No measurement is named for this step, so it is drawn as an unconfirmed link.
The measurement behind this step
Inhibition of calcium influx during membrane depolarisation reduces vascular smooth muscle contraction and peripheral resistance. The label describes diltiazem as a potent dilator of both epicardial and subendocardial coronary arteries, and records that spontaneous and ergonovine-induced coronary spasm is inhibited.
The signal passing from the top chambers to the bottom ones travels on the same kind of calcium current. Slowing it is how the drug brings down a racing pulse in atrial fibrillation.
╌╌Described, with no measurement named. No measurement is named for this step, so it is drawn as an unconfirmed link.
The measurement behind this step
Diltiazem prolongs AV nodal refractory period without significantly prolonging sinus node recovery time except in sick sinus syndrome. Use-dependence means the effect is larger at high atrial rates, which is why the intravenous form controls a fast ventricular response.
A slower heart working against lower pressure needs less oxygen, and wider coronary arteries deliver more. Angina eases from both directions at once.
╌╌Described, with no measurement named. No measurement is named for this step, so it is drawn as an unconfirmed link.
The measurement behind this step
The label attributes increased exercise tolerance to reduced myocardial oxygen demand through lower heart rate and systemic pressure at submaximal and maximal workloads, combined with coronary dilatation at drug levels causing little or no negative inotropic effect in humans with normal ventricular function.
The same effect is harmful in a heart that is already failing
A heart that has just been damaged and is holding fluid cannot afford any reduction in its squeezing power. In that group, this drug made things worse.
──Measured in people. Written by a person from the study named beside the step. Not signed off as a reviewed claim.
The measurement behind this step
In MDPIT, patients with radiographic pulmonary congestion had a cardiac event hazard ratio of 1.41 (95% CI 1.01 to 1.96) on diltiazem, against 0.77 (0.61 to 0.98) in patients without it, interaction p=0.0042. The label now contraindicates use in acute myocardial infarction with pulmonary congestion documented on admission.
Diltiazem also slows the liver enzyme that clears many other drugs, so those drugs build up. With modern blood thinners this shows up as bleeding.
──Measured in people. Written by a person from the study named beside the step. Not signed off as a reviewed claim.
The measurement behind this step
Diltiazem is a CYP3A4 substrate and moderate inhibitor. In 204,155 Medicare patients on apixaban or rivaroxaban, starting diltiazem rather than metoprolol was associated with a serious bleeding hazard ratio of 1.21 (95% CI 1.13 to 1.29), rising to 1.29 above 120 mg daily.
No suggested links are held for this record, so nothing is hidden from this path.
What we know
The record describes 6 steps from taking it to an effect in a person.
How we know it
Each step names the study behind it in the technical detail beside it.
What this does not prove
A change inside the body is a reason to look. It is not a result in a person.
Why it matters
A reader can see exactly where the chain stops being measured in people.
What we still do not know
No reviewed claim binds any of these steps to a named population.
What is missing or unclear◇Read from sources, not yet reviewed
Were people like you studied?
RNAWiki cannot tell whether a study fits you. It can show who was in it, and where the result stops carrying.
Who was studied
People similar to this profile were included.
Adults with angina, including the vasospastic form where it is a first choice; adults with high blood pressure; and, intravenously, patients whose atrial fibrillation is running too fast. Not people with sick sinus syndrome or high-grade heart block without a pacemaker, and not people with a recent infarction and fluid on the lungs.
Who is missing from the studies
Which groups were under-represented in the studies has not been recorded for this substance. Pregnancy, breastfeeding, children, older adults, and people with liver or kidney conditions are commonly excluded from trials; nothing here says whether they were.
What the label states about particular groups
On pediatric, the label states: “Safety and effectiveness in pediatric patients have not been established.”
US prescribing information · 73b3607a-99d0-44d8-92ef-0074684c9d7d · read 2026-08-30
On older people, the label states: “Clinical studies of diltiazem did not include sufficient numbers of subjects aged 65 and over to determine whether they respond differently from younger subjects.”
US prescribing information · 73b3607a-99d0-44d8-92ef-0074684c9d7d · read 2026-08-30
On people who are pregnant, the label states: “Risk Summary The available data from the published literature over decades of use with diltiazem during pregnancy have not identified a drug associated risk of major birth defects, miscarriage, or adverse maternal or fetal outcomes.”
US prescribing information · 73b3607a-99d0-44d8-92ef-0074684c9d7d · read 2026-08-30
On people who are breastfeeding, the label states: “Risk Summary Diltiazem is excreted in human milk.”
US prescribing information · 73b3607a-99d0-44d8-92ef-0074684c9d7d · read 2026-08-30
Where the result stopped carrying
MDPIT found no overall mortality benefit after infarction and a clear harm signal in patients with pulmonary congestion
NORDIL lowered systolic pressure 3 mmHg less than the comparator regimen and matched it on events, which answers neither question cleanly
The CYP3A4 interaction with the direct oral anticoagulants was quantified in 2024, more than forty years after approval and a decade after those anticoagulants launched
Second- or third-degree AV block occurred in 0.40% of the trial database, and one patient had 2 to 5 second asystole after a single 60 mg dose
This is a scope explorer, not a diagnosis engine.
It shows who was studied so you can see whether people similar to you were included.
RNAWiki cannot tell whether a study fits you. It can show who was in it.
What it would be like to take◇Read from sources, not yet reviewed
Why it might seem to do nothing
A real effect and a noticed effect are different things. These are the recorded reasons the two come apart.
It was studied in different people
The people in the studies were not much like the reader.
On this record: Which groups were under-represented in the studies has not been recorded for this substance. Pregnancy, breastfeeding, children, older adults, and people with liver or kidney conditions are commonly excluded from trials; nothing here says whether they were.
The evidence may simply be wrong
Small early studies often do not hold up.
On this record: RNAWiki has not yet published a reviewed conclusion for this use.
Other reasons RNAWiki checked and found nothing for (11)
It was studied for a different goal
The studies measured something else entirely. Nothing in this record points to this reason.
A different form was studied
The studied form is not the form on the shelf. Nothing in this record points to this reason.
There was nothing to correct
Where a level is already normal, topping it up may change nothing. Nothing in this record points to this reason.
Something else had to happen too
In the studies it was paired with training, a diet or another treatment. Nothing in this record points to this reason.
The change is too small to feel
A real change can still sit below what a person notices. Nothing in this record points to this reason.
Day-to-day swing hides it
Sleep, food, stress and time of day move most numbers more than this would. Nothing in this record points to this reason.
Not enough time yet
The studies ran longer than the person has waited. Nothing in this record points to this reason.
It was not taken as studied
Missed days change the result, and studies count them. Nothing in this record points to this reason.
Something else changed at the same time
Two changes at once cannot be told apart afterwards. Nothing in this record points to this reason.
The product may not be what it says
Contents of a sold product are not always what the label states. Nothing in this record points to this reason.
No recorded reason
RNAWiki has nothing stored that would explain it. Nothing in this record points to this reason.
None of these is a reason to take more. Taking more is not a step this page ever suggests.
What it would be like to take◇Read from sources, not yet reviewed
What taking it involves
The recorded facts about getting hold of it and using it. Nothing here is a suggestion about what you should do.
How it is supplied
Given by a clinician
❝ Quoted from a source
Where this came from
Copied from a source RNAWiki stored, with the source named.
Read from the recorded approval status.
No source is stored against this line.
Form and route
Immediate-release tablet, several extended-release capsule and tablet formats, and an intravenous bolus and infusion
✎ Source-linked record
Where this came from
A person wrote this into the record with the study named beside it. No reviewer has signed it off.
The form and route recorded on this substance.
No source is stored against this line.
Who oversees it
RNAWiki has not recorded a supervision or regulatory status for this substance.
❝ Quoted from a source
Where this came from
Copied from a source RNAWiki stored, with the source named.
No register row and no identity class settled the question.
No source is stored against this line.
What is in the pack
The oral forms are not interchangeable: the many extended-release products differ in release profile and are approved separately, which is why 177 distinct products are listed in the pricing survey. The intravenous route exists for one job the oral route cannot do quickly enough — bringing down a fast ventricular rate in atrial fibrillation or flutter, and converting paroxysmal supraventricular tachycardia.
✎ Source-linked record
Where this came from
A person wrote this into the record with the study named beside it. No reviewer has signed it off.
Recorded notes on how this is sold and what that means for what is in the pack.
No source is stored against this line.
Where it is registered
Regulatory records are listed in the technical disclosure at the foot of this page.
# Counted from records
Where this came from
A count of rows RNAWiki holds. It describes our records, not your body.
Register entries are stored per jurisdiction and shown with their dates.
No source is stored against this line.
Why people stop
Not recorded.
∅ Nothing recorded
Where this came from
RNAWiki holds nothing here and says so rather than guessing.
No record of why people stopped taking it is stored for this substance.
No source is stored against this line.
What it would be like to take◇Read from sources, not yet reviewed
What can go wrong
Sorted by where each line came from. A regulator's label and a report somebody sent in are not the same kind of fact.
·Worth asking a clinician aboutWritten into the record from the studies named on this page
Contraindicated in sick sinus syndrome and in second- or third-degree AV block without a functioning ventricular pacemaker, in systolic pressure below 90 mmHg, in hypersensitivity, and in acute myocardial infarction with pulmonary congestion documented by x-ray on admission. Conduction effects are additive with beta-blockers and digitalis. Worsening congestive heart failure has been reported where ventricular function was already impaired. As a CYP3A4 inhibitor it raises exposure to a long list of co-prescribed drugs, and the largest quantified consequence is bleeding on apixaban or rivaroxaban.
Nobody counted how many people took this and were fine, so this cannot be turned into a rate.
Over a long time. No completed tested study window is recorded, so long-term effects are not established by the registry record.
Groups the studies covered thinly. Which groups were under-represented in the studies has not been recorded for this substance. Pregnancy, breastfeeding, children, older adults, and people with liver or kidney conditions are commonly excluded from trials; nothing here says whether they were.
What is missing or unclear◇Read from sources, not yet reviewed
Does the exact form matter?
Evidence belongs to the exact thing that was tested. A different salt, a different mixture or a different preparation is a different question.
The form that was studied
Immediate-release tablet, several extended-release capsule and tablet formats, and an intravenous bolus and infusion
✎ Source-linked record
Where this came from
A person wrote this into the record with the study named beside it. No reviewer has signed it off.
The form used in the studies cited on this page.
No source is stored against this line.
What is sold
The intravenous route exists for one job the oral route cannot do quickly enough — bringing down a fast ventricular rate in atrial fibrillation or flutter, and converting paroxysmal supraventricular tachycardia.
✎ Source-linked record
Where this came from
A person wrote this into the record with the study named beside it. No reviewer has signed it off.
Recorded notes on which forms are sold and how they compare.
No source is stored against this line.
What is recorded as being sold
319 products list this as an active ingredient in the United States drug directory. 319 of them contain it and nothing else.
FDA National Drug Code directory · 0409-4350 · read 2026-08-29
They are sold as capsule, coated, extended release, capsule, extended release, injection, injection, powder, lyophilized, for solution, injection, solution and powder, taken intravenous and oral.
FDA National Drug Code directory · 0409-4350 · read 2026-08-29
The regulator's established pharmacologic class for it is calcium channel antagonists [moa], calcium channel blocker [epc] and cytochrome p450 3a4 inhibitors [moa].
FDA National Drug Code directory · 0409-4350 · read 2026-08-29
117 published labels name it as an active ingredient. 117 of them describe this substance alone, which is where its own label text on this page comes from.
US prescribing information · 2dc2b889-8443-4f7f-83be-86c68e179804 · read 2026-08-29
Those labels are classed as human prescription drug.
US prescribing information · 2dc2b889-8443-4f7f-83be-86c68e179804 · read 2026-08-29
5 marketed supplement labels list this ingredient, classed as botanical with nutrients and other combinations.
Those labels carry all other, nutrient and qualified health claims. A claim of that kind is written by the manufacturer and is not assessed by any regulator, so its presence says nothing about whether it is true.
Recorded price in US: 0.04994–2.54181 USD per one unit as the pricing file counts it — a tablet, capsule, patch or single item, across 134 priced products whose strengths and pack forms differ, as of 2026-08-26, paid by retail pharmacies buying the product, as surveyed by the Centers for Medicare & Medicaid Services. It is not a list price, an insurance price, or what anyone pays at a counter..
Recorded source · 2026-08-26 · read 2026-08-28
Evidence carries across two names for one substance. It does not carry across a salt, a mirror form or a mixture.
What it would be like to take◇Read from sources, not yet reviewed
What you could measure
This one is decided with a clinician, so this section holds questions to ask rather than a plan to run.
RNAWiki could not confidently classify this substance, so no self-experiment plan is offered.
Questions worth asking
Which of the trials of Diltiazem studied people like me?
What was measured, and for how long?
Was the result a laboratory value or a health outcome?
What would we watch for, and when would we stop?
Tracking can show whether something changed for you. It cannot show what caused it.
RNAWiki records evidence. It does not say whether this substance is right for you.
What is missing or unclear◇Read from sources, not yet reviewed
Claims that go past the evidence
Things said about this substance that sound reasonable, and the exact step that is missing between the evidence and the claim.
✗Goes past the evidence
That improving exercise tolerance in stable angina translates into fewer infarctions or deaths, which no diltiazem trial has shown
Why it sounds right. It follows from something real on this page: a body step, an animal result or a related finding.
The missing step. Nobody measured this in people for this use, or the study that did measure it did not show it.
What would change this
A study in people, for this exact use, measuring this exact thing, that a reviewer signs off.
RNAWiki has not yet published a reviewed conclusion for this use.
✗Goes past the evidence
That a neutral trial result means a neutral drug — MDPIT concealed benefit and harm of similar size in opposite subgroups
Why it sounds right. It follows from something real on this page: a body step, an animal result or a related finding.
The missing step. Nobody measured this in people for this use, or the study that did measure it did not show it.
What would change this
A study in people, for this exact use, measuring this exact thing, that a reviewer signs off.
RNAWiki has not yet published a reviewed conclusion for this use.
✗Goes past the evidence
That the lower stroke rate in NORDIL is a diltiazem property rather than one of several secondary endpoints in a trial whose primary was flat
Why it sounds right. It follows from something real on this page: a body step, an animal result or a related finding.
The missing step. Nobody measured this in people for this use, or the study that did measure it did not show it.
What would change this
A study in people, for this exact use, measuring this exact thing, that a reviewer signs off.
RNAWiki has not yet published a reviewed conclusion for this use.
✗Goes past the evidence
That being a calcium channel blocker makes diltiazem interchangeable with amlodipine — they bind different sites and do different things to the AV node
Why it sounds right. It follows from something real on this page: a body step, an animal result or a related finding.
The missing step. Nobody measured this in people for this use, or the study that did measure it did not show it.
What would change this
A study in people, for this exact use, measuring this exact thing, that a reviewer signs off.
RNAWiki has not yet published a reviewed conclusion for this use.
What is missing or unclear◇Read from sources, not yet reviewed
What nobody knows yet
Open questions, each with why it is open and what would close it.
Missing populations
Which groups were under-represented in the studies has not been recorded.
Why it matters. Recorded by the evidence model as a gap on this record.
What would answer it
A study that measures it, and a reviewer to sign it off.
Last checked 2026-09-04. Searched: The sources listed in the receipts at the foot of this page.
Missing long-term data
No completed tested study window is recorded.
Why it matters. Recorded by the evidence model as a gap on this record.
What would answer it
A study that measures it, and a reviewer to sign it off.
Last checked 2026-09-04. Searched: The sources listed in the receipts at the foot of this page.
No reviewed conclusion
RNAWiki has not yet published a reviewed conclusion for this use.
Why it matters. Recorded by the evidence model as a gap on this record.
What would answer it
A study that measures it, and a reviewer to sign it off.
Last checked 2026-09-04. Searched: The sources listed in the receipts at the foot of this page.
Missing interaction studies
No interaction was found in the registers checked. Not finding one is not the same as showing there is none.
Why it matters. Recorded by the evidence model as a gap on this record.
What would answer it
A study that measures it, and a reviewer to sign it off.
Last checked 2026-09-04. Searched: The sources listed in the receipts at the foot of this page.
Formulation uncertainty
Several salts, forms or products of Diltiazem are recorded. Results from one form may not transfer to another.
Why it matters. Recorded by the evidence model as a gap on this record.
What would answer it
A study that measures it, and a reviewer to sign it off.
Last checked 2026-09-04. Searched: The sources listed in the receipts at the foot of this page.
Mechanism not reviewed
No reviewed mechanism story exists for this substance.
Why it matters. Recorded by the evidence model as a gap on this record.
What would answer it
A study that measures it, and a reviewer to sign it off.
Last checked 2026-09-04. Searched: The sources listed in the receipts at the foot of this page.
What happened in people◇Read from sources, not yet reviewed
Check any of this yourself
Every line above traced back to the study it came from. This is the technical layer, and the vocabulary changes here.
Every line above can be traced to the study named beside it. Follow the link and read it.
MDPIT: no overall effect on death, and clear harm in one subgroup
In plain words
Nearly two and a half thousand people were given diltiazem or a dummy tablet after a heart attack. Exactly as many died in each group. Underneath that flat result were two opposite effects: fewer heart events in patients with clear lungs, and more in patients whose lungs had fluid.
What was measured
Total mortality and first recurrent cardiac events after myocardial infarction, with a prespecified interaction by pulmonary congestion
Effect estimate
No reviewed effect estimate exists for this record.
Limits
This entry records a failure.
From the source
The Multicenter Diltiazem Postinfarction Trial randomised 2,466 patients with previous infarction to diltiazem 240 mg daily (n=1,234) or placebo (n=1,232), followed 12 to 52 months with a mean of 25. Total mortality was nearly identical: 167 against 166. First recurrent cardiac events, defined as cardiac death or non-fatal reinfarction, were 202 against 226 (Cox hazard ratio 0.90, 95% CI 0.74 to 1.08). A significant bidirectional interaction with radiographic pulmonary congestion was found at p=0.0042: in the 1,909 patients without congestion the hazard ratio was 0.77 (95% CI 0.61 to 0.98), and in the 490 with congestion it was 1.41 (95% CI 1.01 to 1.96). The same pattern appeared when ejection fraction was dichotomised at 0.40. The authors conclusion is that the neutral overall effect concealed a benefit in the majority without left ventricular dysfunction and an increase in events in the minority with it.
Written into the record, not signed off as a reviewed claim
The harm signal became a line in the contraindications
In plain words
A trial found that a particular group of patients did worse on this drug. Thirty-odd years later, that group is named in the contraindications on the box. This is what the evidence system is supposed to do and rarely gets credit for.
What was measured
That a neutral overall trial result means a drug is neutral for everyone in the trial — MDPIT is the counter-example, and its subgroup is now on the label
Effect estimate
No reviewed effect estimate exists for this record.
Limits
See the technical detail.
From the source
The Cardizem CD label lists among its contraindications: patients with acute myocardial infarction and pulmonary congestion documented by x-ray on admission. That sentence is MDPIT written into regulatory text — the 490-patient subgroup in which cardiac events rose 41% on diltiazem. The Warnings section adds the corresponding physiology: although hemodynamic studies in humans with normal ventricular function have not shown a reduction in cardiac index or consistent negative effects on contractility, worsening of congestive heart failure has been reported in patients with pre-existing impairment of ventricular function, and experience of the combination with beta-blockers in that setting is limited. A subgroup finding that becomes a contraindication is unusual; most disappear into a discussion section.
Written into the record, not signed off as a reviewed claim
A 21% higher rate of serious bleeding with two of the commonest anticoagulants
In plain words
Diltiazem slows the breakdown of apixaban and rivaroxaban, so more of the blood thinner stays in the body. In two hundred thousand Medicare patients, those started on diltiazem bled seriously more often than those started on a beta-blocker.
What was measured
Composite of bleeding-related hospitalisation and death with recent evidence of bleeding, diltiazem against metoprolol
Effect estimate
No reviewed effect estimate exists for this record.
Limits
This entry records a failure.
From the source
A retrospective cohort of 204,155 United States Medicare beneficiaries aged 65 or over with atrial fibrillation, newly started on apixaban or rivaroxaban and simultaneously on diltiazem (n=53,275) or metoprolol (n=150,880), followed a median of 120 days. The primary composite of bleeding-related hospitalisation and death with recent evidence of bleeding was raised on diltiazem: rate difference 10.6 per 1,000 person-years (95% CI 7.0 to 14.2), hazard ratio 1.21 (95% CI 1.13 to 1.29). Bleeding-related hospitalisation alone had a hazard ratio of 1.22 (1.13 to 1.31), and death with recent evidence of bleeding 1.19 (1.05 to 1.34). The effect was dose-related: above 120 mg daily the rate difference was 15.1 per 1,000 person-years (HR 1.29, 1.19 to 1.39) against 6.7 at lower doses (HR 1.13, 1.04 to 1.24), and comparing high against low dose directly gave a hazard ratio of 1.14 (1.02 to 1.26). Ischaemic stroke, systemic embolism and death without evidence of bleeding did not differ. This is a cohort study, not a randomised trial, and the exposure comparison is between two drugs given for the same purpose in the same population, which is the design that gets closest to randomisation without being it.
Written into the record, not signed off as a reviewed claim
NORDIL: as good as the old drugs on events, and worse at lowering blood pressure
In plain words
Ten thousand people with high blood pressure were randomised to diltiazem or to the standard combination of a diuretic and a beta-blocker. The rate of strokes and heart attacks came out identical, even though diltiazem lowered the top number by three points less.
What was measured
Composite of fatal and non-fatal stroke, myocardial infarction and other cardiovascular death, diltiazem against diuretic or beta-blocker therapy
Effect estimate
No reviewed effect estimate exists for this record.
Limits
See the technical detail.
From the source
NORDIL was a prospective, randomised, open, blinded-endpoint study of 10,881 patients aged 50 to 74 with diastolic pressure of 100 mmHg or more, in Norwegian and Swedish health centres. Blood pressure fell 20.3/18.7 mmHg on diltiazem against 23.3/18.7 mmHg on diuretics, beta-blockers or both, a significant difference in systolic reduction (p<0.001). The combined primary endpoint of fatal and non-fatal stroke, myocardial infarction and other cardiovascular death occurred in 403 against 400 patients, 16.6 against 16.2 events per 1,000 patient-years, relative risk 1.00 (95% CI 0.87 to 1.15, p=0.97). Stroke alone favoured diltiazem: 6.4 against 7.9 per 1,000 patient-years, RR 0.80 (0.65 to 0.99, p=0.04). Myocardial infarction went the other way without reaching significance: 7.4 against 6.3 per 1,000 patient-years, RR 1.16 (0.94 to 1.44, p=0.17). Equal outcomes at unequal blood pressure is an interesting result and it is also the kind of result that generates two opposite press releases.
Written into the record, not signed off as a reviewed claim
Exercise tolerance is the measured angina endpoint, and it is not an event count
In plain words
What the drug is licensed to do in angina is improve how far you can walk on a treadmill before the chest pain starts. No trial has shown it prevents heart attacks in stable angina.
What was measured
That better exercise tolerance and fewer anginal episodes translate into fewer infarctions or deaths — not shown for this drug in any trial that looked
Effect estimate
No reviewed effect estimate exists for this record.
Limits
See the technical detail.
From the source
The Cardizem LA indication is improving exercise tolerance in patients with chronic stable angina, and the mechanism section attributes that to reduced myocardial oxygen demand through lower heart rate and blood pressure at submaximal and maximal workloads, plus coronary dilatation. The label also records that diltiazem is a potent dilator of both epicardial and subendocardial coronary arteries and inhibits spontaneous and ergonovine-induced spasm, which is the basis for the vasospastic angina indication. None of that is an outcome claim. In the one large post-infarction trial, total mortality was identical, and in the one large hypertension outcome trial the composite was identical to the comparator. Diltiazem is a symptomatic and physiological drug with no demonstrated effect on survival in any population studied.
Source
CARDIZEM LA and CARDIZEM CD United States prescribing information, Indications and Clinical Pharmacology sections; MDPIT, N Engl J Med 1988;319:385-392; NORDIL, Lancet 2000;356:359-365
Role in the trial
Not matched to a registered study
Identity check
no open identity hold
Audit mark
caution
Review state
Written into the record, not signed off as a reviewed claim
Conduction block is rare, additive and occasionally abrupt
In plain words
Diltiazem slows the electrical relay between the heart chambers. In four cases per thousand that slowing becomes a block. Added to a beta-blocker or digoxin, the effect compounds.
What was measured
Second- or third-degree AV block in 13 of 3,290 patients (0.40%) in the trial database
Effect estimate
No reviewed effect estimate exists for this record.
Limits
This entry records a failure.
From the source
The label records that diltiazem prolongs AV node refractory periods without significantly prolonging sinus node recovery time except in sick sinus syndrome, and that this rarely produces abnormally slow heart rates or second- or third-degree AV block in 13 of 3,290 patients, or 0.40%. Concomitant use with beta-blockers or digitalis may have additive effects on conduction. One patient with Prinzmetal angina developed periods of asystole of 2 to 5 seconds after a single 60 mg dose. Contraindications include sick sinus syndrome and second- or third-degree AV block without a functioning ventricular pacemaker, and systolic pressure below 90 mmHg.
Source
CARDIZEM CD United States prescribing information, Warnings and Contraindications sections
Role in the trial
Not matched to a registered study
Identity check
no open identity hold
Audit mark
caution
Review state
Written into the record, not signed off as a reviewed claim
How many documents were read
111 documents were read for this substance.
RNAWiki source record
10 of them state the same proteinBinding, and they agree.
RNAWiki source record
10 of them state the same volumeOfDistribution, and they agree.
RNAWiki source record
Where else this substance is registered
FDA substance identifier (UNII)
OLH94387TE
CAS registry number
42399-41-7
PubChem compound
39186
RxNorm concept
203211
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What is missing or unclear◇Read from sources, not yet reviewed
How this medicine reached us
Kept near the foot of the page. A historical event moves up only when it changes something about this substance today.
What the approval register records
70 approved applications cover products containing this substance. The earliest was NDA018602, approved 19821105 to BAUSCH.
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What is not here
7 questions this page could not answer
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The older medicine-wide conclusion held in this record
Written for a clinical reader, and about the medicine as a whole rather than about one indication, population and set of trials. RNAWiki does not treat it as a programme conclusion and no reviewer has signed it off in that form. It is here word for word because it is what the record holds.
A non-dihydropyridine calcium blocker that widens coronary arteries and slows conduction through the AV node, which in 2,466 post-infarction patients produced identical total mortality to placebo while cutting cardiac events by 23% in the 1,909 without pulmonary congestion and raising them by 41% in the 490 who had it — a finding now written into its own contraindications.
3.0 to 4.5 hours; The plasma elimination half-life of diltiazem is approximately 3.0 to 4.5 hours.
bioavailabilitypharmacokinetics
40 %; The absolute bioavailability of an oral dose of an immediate-release formulation (compared to intravenous administration) is approximately 40%.
metabolismpharmacokinetics
and Metabolism Diltiazem is well absorbed from the gastrointestinal tract but undergoes substantial hepatic first-pass effect.
recorded 2026-08-07 · last checked 2026-09-04
Q6
Which 25 trials of Diltiazem posted no result?
Posted no result
25 of 25 completed trials
Registrations
NCT00000478, NCT00000556, NCT00039975, NCT00318201, NCT00893100 and NCT04222855, and 19 more
Completion dates
oldest 1997-06; newest 2024-04-11
Show the evidence
Trial
NCT00000478
1997-06
NCT00000556
2002-09
NCT00039975
2004-04
NCT00318201
2007-12
NCT00893100
2008-12
NCT04222855
2009-05-30
14 further recorded trials
NCT00712894
2009-08
NCT00593463
2010-05
NCT01124760
2010-07
NCT00313157
2010-09
NCT01211808
2010-10
NCT01655303
2011-12
NCT01852565
2013-09-30
NCT01408524
2013-12
NCT02526888
2015-11-01
NCT02807909
2016-08
NCT00223717
2017-01
NCT02947711
2017-01
NCT03930433
2019-03-31
NCT04467931
2020-12-31
Q7
At the median, Diltiazem's trials enrolled 38 people — anything larger?
Median enrolment
38
Largest enrolment
22213
Registered trials counted
60
Q8
What do 8 spontaneous reports say about Diltiazem — and not say?
These are reports people sent to a regulator. They do not show the medicine caused the reaction. Nobody counted how many people took the medicine and reported nothing. The same event can be reported more than once, and many reports are incomplete. News coverage, lawsuits and new warnings change how often people report. A count is not a rate and not a risk.
Diltiazem appears in spontaneous reports to regulators. Across the 1 most-reported reaction term, 8 reaction mentions were counted: atrioventricular block complete 8. FAERS via Open Targets · CHEMBL1200805 · 2026-06-24
Diltiazem is both a substrate and an inhibitor of the Pg-p and cytochrome P450 3A4 enzyme system which may affect exposure to diltiazem and concomitant drugs metabolized by those pathways.
drug_interactions
The effect may be mediated by cimetidine’s known inhibition of hepatic cytochrome P450, the enzyme system responsible for the first-pass metabolism of diltiazem.
drug_interactions
Coadministration of diltiazem with rifampin or any known CYP3A4 inducer should be avoided when possible, and alternative therapy considered.
drug_interactions
Statins: Diltiazem is an inhibitor of CYP3A4 and has been shown to increase significantly the AUC of some statins.
drug_interactions
The risk of myopathy and rhabdomyolysis with statins metabolized by CYP3A4 is increased with concomitant use of diltiazem.
drug_interactions
When possible, use a non-CYP3A4-metabolized statin with diltiazem.
ChEMBL 37 — CC BY-SA 3.0 Unported · ClinicalTrials.gov — US Government work · Open Targets 26.06 — CC0 · mixed register set; per-register licences in docs/specs/corpus-20k-sources.md · openFDA / DailyMed — US Government work
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