diltiazem
Brand names: Cardizem, Tiazac
Diltiazem is a medicine that helps lower high blood pressure and prevent chest pain. It belongs to a class of drugs called calcium channel blockers.
Drug Shortage Alert
diltiazem is currently listed as to be discontinued by the FDA. Affected manufacturer: Hospira, Inc., a Pfizer Company.
View all drug shortages →Drug Pricing (NADAC)
Generic Price
$0.23/unit
Generic Available
Yes (32 manufacturers)
Pricing data from NADAC (CMS), effective December 18, 2024. Compare all drug costs →
What it does
Diltiazem is used to treat high blood pressure.
Common side effects
Swelling in your ankles or feet, Headache, Dizziness
Key warnings
Diltiazem can interact with other heart medications.
How It Works
Diltiazem works by relaxing blood vessels, which lowers blood pressure. It also reduces the heart's workload, which can prevent chest pain. This medicine blocks calcium from entering heart and blood vessel cells.
How to Take It
Take diltiazem capsules once a day. Your doctor will adjust your dose based on your needs. You may need higher doses if you are switched from another diltiazem product. Do not change your dose without talking to your doctor.
Pregnancy & Breastfeeding
Tell your doctor if you are pregnant, plan to become pregnant, or are breastfeeding. It is not known if diltiazem will harm your unborn baby. Diltiazem passes into breast milk, so talk to your doctor about breastfeeding while taking this medicine.
Missed Dose
If you miss a dose, take it as soon as you remember. If it is almost time for your next dose, skip the missed dose and continue with your regular schedule.
Storage
Store diltiazem capsules at room temperature, away from excessive humidity.
Side Effects (from patient reports)
Based on 22,336 FDA adverse event reports.
FDA Adverse Event Report Analysis
Detailed analysis of 33,620 reports from the FDA Adverse Event Reporting System (FAERS). Reports span 2003–2025.
Total Reports
33,620
Death-Related Reports
4,917
Hospitalization Reports
14,360
Top Indication
Product Used For Unknown Indication
Gender Distribution
Age Distribution
Most Reported Adverse Reactions (FAERS)
| # | Reaction | Reports |
|---|---|---|
| 1 | DYSPNOEA | 3,202 |
| 2 | FATIGUE | 2,638 |
| 3 | NAUSEA | 2,372 |
| 4 | PAIN | 2,365 |
| 5 | DIZZINESS | 2,091 |
| 6 | DIARRHOEA | 2,045 |
| 7 | DRUG INEFFECTIVE | 1,997 |
| 8 | FALL | 1,954 |
| 9 | HEADACHE | 1,929 |
| 10 | ATRIAL FIBRILLATION | 1,754 |
| 11 | ASTHENIA | 1,705 |
| 12 | PNEUMONIA | 1,605 |
| 13 | ARTHRALGIA | 1,548 |
| 14 | HYPOTENSION | 1,494 |
| 15 | PAIN IN EXTREMITY | 1,449 |
Reactions in Death Reports
Reactions in Hospitalization Reports
Source: FDA FAERS (Adverse Event Reporting System) FDA FAERS (Adverse Event Reporting System) Reports are voluntary and do not establish causation
Serious Warnings
Diltiazem can interact with other heart medications. Tell your doctor if you take beta-blockers or digoxin. Using diltiazem with these drugs can cause heart problems. Your doctor may need to adjust your dosages.
Known Drug Interactions
Intervention: For patients taking verapamil, diltiazem, or dronedarone, do not exceed ezetimibe and simvastatin 10 mg/10 mg daily.
Mechanism: Diltiazem can increase the levels of the cholesterol medicine in your blood, which may lead to muscle problems.
What to do: Your doctor should limit your dose of the combination medicine to 10 mg/10 mg daily.
Intervention: For patients taking verapamil, diltiazem, or dronedarone, do not exceed VYTORIN 10/10 mg daily.
Mechanism: Diltiazem slows down the breakdown of simvastatin in your body, which can lead to higher levels of the drug in your blood. This increases the risk of serious muscle damage.
What to do: Do not take more than 10/10 mg of VYTORIN daily if you are also taking diltiazem.
Intervention: For patients taking verapamil, diltiazem, or dronedarone, do not exceed ezetimibe and simvastatin 10 mg/10 mg daily.
Mechanism: Diltiazem blocks the enzymes that break down simvastatin, causing the drug to stay in your body longer. This can lead to a higher risk of muscle pain or damage.
What to do: Your doctor should limit your simvastatin dose to 10 mg daily while you are taking diltiazem.
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Mechanism: Diltiazem can slow down the liver's ability to break down theophylline. This can cause the medicine to build up in your body and reach toxic levels.
What to do: Your doctor may need to lower your theophylline dose while you are taking diltiazem. Watch for signs of too much medicine, such as nausea, tremors, or a fast heartbeat.
Rifampin : Coadministration of rifampin with diltiazem lowered the diltiazem plasma concentrations to undetectable levels. Avoid coadministration of diltiazem with rifampin or any known CYP3A4 inducer.
Mechanism: Rifampin speeds up how quickly your body breaks down diltiazem, which can cause the diltiazem to disappear from your blood and stop working.
What to do: You should avoid taking these two medications together.
Common Questions
Can I take diltiazem with other medications?
How long does it take for diltiazem to start working?
Can I drink alcohol while taking diltiazem?
What should I do if I experience side effects?
Can I stop taking diltiazem suddenly?
Does diltiazem affect my ability to drive or operate machinery?
How often should I check my blood pressure?
Can diltiazem cure my high blood pressure or angina?
What if I have kidney or liver problems?
Are there any foods I should avoid while taking diltiazem?
What are the common side effects of diltiazem?
Does diltiazem interact with other medications?
What drug class is diltiazem?
Is diltiazem safe during pregnancy?
Has diltiazem been recalled?
Is diltiazem currently in shortage?
Active Recalls
cGMP Deviations: Presence of N-nitroso-Desmethyl-Diltiazem impurity above FDA recommended interim limit.
Glenmark Pharmaceuticals Inc., USA
cGMP Deviations: Presence of N-nitroso-Desmethyl-Diltiazem impurity above FDA recommended interim limit.
Glenmark Pharmaceuticals Inc., USA
cGMP Deviations: Presence of N-nitroso-Desmethyl-Diltiazem impurity above FDA recommended interim limit.
Glenmark Pharmaceuticals Inc., USA
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Medication Guides
Understanding Drug Interactions
How CYP450 enzymes, inhibitors, and inducers affect your medications
Generic vs Brand Name Drugs
FDA requirements, cost savings, and when the difference matters
Narrow Therapeutic Index Drugs
Why some drugs demand precise dosing and monitoring
Common Drug Interactions
Dangerous medication combinations and how to protect yourself
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What the FDA Data Shows for diltiazem
The FDA label for diltiazem (sold under brand names such as Cardizem, Tiazac) classifies it as a prescription-only medication in the Calcium Channel Blocker class. Diltiazem is used to treat high blood pressure. Official labeling lists 5 commonly reported side effects, including Swelling in your ankles or feet, Headache, Dizziness.
Post-market surveillance from the FDA Adverse Event Reporting System (FAERS) captures real-world experience. For this drug, FAERS contains 22,336 voluntary reports. The database also lists 46 documented drug interactions derived from FDA labeling, with the top-flagged interaction rated major severity. NADAC pricing from CMS shows a generic unit cost of $0.23.
Report counts do not establish causation — a FAERS entry documents a temporal association, not proof that the drug produced the outcome. Widely prescribed medications naturally accumulate more reports than niche therapies, so raw totals must be interpreted alongside total exposure. Shortage status, recall history (currently 3 recall records on file), and patent information further shape supply and switching decisions. This page summarizes public FDA data for educational purposes only and is not a substitute for professional medical advice — always consult a licensed healthcare provider before starting, stopping, or changing any medication.
Data Sources
Drug labeling: FDA Drug Labels (SPL/DailyMed). Adverse events: FDA Adverse Event Reporting System (FAERS). Pricing: CMS National Average Drug Acquisition Cost (NADAC). Shortage status: FDA Drug Shortages Database.
FAERS reports are voluntary and do not establish causation. Drug interactions are derived from FDA labeling and clinical references. Always consult a healthcare professional before making medication decisions.
Last updated: August 20, 2025
Read our methodology — how this data is sourced, computed, and verified.
All federal data sources used on this page
- FDA Orange Book — approved drug products with therapeutic equivalence. accessdata.fda.gov/cder/ob
- FDA DailyMed — NIH-hosted drug labeling for FDA-approved meds. dailymed.nlm.nih.gov
- FDA Adverse Event Reporting System (FAERS) — post-marketing safety surveillance. fda.gov/drugs/faers
- NLM RxNorm — standardized clinical drug nomenclature. nlm.nih.gov/research/umls/rxnorm
- CMS Medicare Part B Drug Average Sales Price Files — federal drug pricing data. cms.gov/medicare/part-b-drugs/asp
- FDA Drug Shortages Database — current and resolved drug shortage tracking. accessdata.fda.gov/drugshortages