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Non-Dihydropyridine Calcium Channel Blocker Pregnancy: Contraindicated during pregnancy and in women of child-bearing potential not using effective contraception (reproductive toxicity in animals). Excreted in breast milk at low concentrations - breast-feeding should be avoided.

Diltiazem

Brand names: Tildiem, Dilzem

Used in: Atrial Fibrillation

Diltiazem is a rate-limiting (non-dihydropyridine) calcium-channel blocker used for angina, hypertension and rate control in certain arrhythmias.

Auto-extracted from the source labelling — not yet independently clinician-verified. These values were distilled from the UK SPC (or the US label where noted) but have not had a clinician sign-off. Confirm against the current SmPC before prescribing.

Adult dose

Dose: 90 mg twice daily (angina, usual initial dose)
Route: Oral
Frequency: Twice daily (12-hour intervals)
Angina: usual initial dose 90 mg twice daily, increased gradually to 120 mg twice daily or 180 mg twice daily if required. Hypertension: usual dose one Adizem-SR 120 mg tablet or capsule twice daily; patients may benefit from titrating up from a lower total daily dose. Elderly and patients with impaired renal or hepatic function: commence at 60 mg twice daily and titrate carefully. Prolonged/sustained-release preparation - swallow whole, do not chew; take with or without food. Not recommended in children. Do not take Adizem-SR capsules at the same time as alcohol.

Dose adjustments

Renal

In the elderly and in patients with impaired renal or hepatic function, commence at 60 mg twice daily and titrate carefully; plasma diltiazem concentrations may be increased.

Dose auto-extracted from UK Summary of Product Characteristics (SPC) via the eMC — not yet clinician-verified. Always confirm against the product SmPC and your local formulary before prescribing.

US labelling (FDA)

Reference — US labelling, may differ from UK

DOSAGE AND ADMINISTRATION Patients controlled on diltiazem alone or in combination with other medications may be switched to diltiazem hydrochloride extended-release capsules, USP at the nearest equivalent total daily dose. Higher doses of diltiazem hydrochloride extended-release capsules, USP may be needed in some patients. Monitor patients closely. Subsequent titration to higher or lower doses may be necessary. There is limited general clinical experience with doses above 360 mg, but doses to 540 mg have been studied in clinical trials. The incidence of side effects increases as the dose increases with first-degree AV block, dizziness, and sinus bradycardia bearing the strongest …

Source: US FDA prescribing information (openFDA / DailyMed), label dated 2025-08-20. Accessed 2026-06-12. US dosing and indications can differ from UK practice — use UK sources for prescribing decisions.

Contraindications

  • Hypersensitivity to diltiazem or excipients
  • Pregnancy and women of child-bearing capacity
  • Severe bradycardia (less than 40 bpm)
  • Second- or third-degree heart block; sick sinus syndrome
  • Decompensated cardiac failure; left ventricular failure with pulmonary congestion
  • Concurrent use with dantrolene infusion (risk of ventricular fibrillation)
  • Concurrent use with lomitapide

Side effects

  • Peripheral oedema (very common)
  • Atrioventricular block, palpitations; bradycardia
  • Headache, dizziness
  • Constipation, dyspepsia, gastric pain, nausea
  • Flushing; orthostatic hypotension

Interactions

  • Dantrolene infusion: contraindicated (risk of lethal ventricular fibrillation)
  • Lomitapide: contraindicated (diltiazem, a moderate CYP3A4 inhibitor, raises lomitapide levels)
  • Lithium: risk of increased lithium-induced neurotoxicity
  • Nitrate derivatives: increased hypotensive effects and faintness
  • Theophylline: increased circulating theophylline levels; alpha-antagonists: increased antihypertensive effect

Clinical monograph

How it works

It blocks L-type calcium channels in the heart and blood vessels, slowing AV-node conduction and heart rate and causing vasodilatation.

Prescribing in practice

  • Avoid combining it with a beta-blocker in most cases (risk of bradycardia and heart block), and avoid in significant left-ventricular systolic dysfunction.
  • Modified-release preparations are not interchangeable — prescribe and dispense by brand.
  • It inhibits CYP3A4, increasing levels of several interacting drugs.

Monitoring

Monitor heart rate, blood pressure and (where relevant) heart-failure status.

Counselling the patient

  • Stay on the same brand of your modified-release product.
  • Report a very slow pulse, dizziness or ankle swelling.

Evidence & guidelines

An option for angina and rate control; avoided with beta-blockers and in heart failure with reduced ejection fraction.

Reference: ESC AF Guidelines 2020; NICE NG196 AF guideline; Drug verified in RxNorm (NLM); confirm dosing against the manufacturer SPC (eMC). Verify against your local formulary and current prescribing references before prescribing. The structured dose values shown have been reviewed by a clinician. Monograph status: clinician-reviewed (2026-07-04).

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