diltiazem hydrochloride: clinical use

Prescribing considerations

• Confirm the indication and release formulation; modified- and prolonged-release brands are not automatically interchangeable.
• Review medicines affecting heart rate, atrioventricular conduction, blood pressure, CYP3A4 or P-glycoprotein.
• Use particular caution in older people and those with hepatic or renal impairment.
• Assess reduced left-ventricular function, first-degree heart block, bradycardia, diabetes, impaired intestinal motility and bronchial hyper-reactivity.
• Check product excipients where relevant; selected formulations contain lactose or sucrose.

Contraindications and cautions

• Hypersensitivity to diltiazem or product excipients.
• Sick sinus syndrome or second- or third-degree atrioventricular block without a functioning pacemaker.
• Severe bradycardia and left-ventricular failure with pulmonary congestion.
• Concomitant intravenous dantrolene or ivabradine.
• Selected products also contraindicate lomitapide, asunaprevir and breastfeeding; other cardiovascular contraindications vary by product.

Monitoring

• Blood pressure, pulse and clinical response.
• ECG and heart-failure symptoms where conduction disease exists or other rate-limiting medicines are used.
• Renal function with existing cardiac disease, severe hypotension or bradycardia.
• Liver function when clinically indicated or symptoms suggest hepatic injury.
• Blood glucose in diabetes and respiratory symptoms in those susceptible to bronchospasm.
• Concentrations or toxicity markers for relevant interacting medicines.

Clinical pharmacology

A benzothiazepine, non-dihydropyridine calcium-channel blocker that causes coronary and systemic vasodilation while slowing sinoatrial and atrioventricular conduction. It is extensively hepatically metabolised, moderately inhibits CYP3A4, weakly inhibits P-glycoprotein and is poorly removed by dialysis.

Formulation and product differences

• Selected products include modified-release tablets, prolonged-release tablets and prolonged-release capsules.
• Release profiles and food instructions differ.
• Continued prescribing by brand helps maintain a consistent release profile and response.
• Do not substitute modified- or prolonged-release products without clinical and pharmaceutical review.

Capsule

Route: Oral

Strengths: 90 mg, 120 mg, 180 mg, 200 mg, 240 mg, 300 mg

Modified-release capsule

Route: Oral

Strengths: 120 mg, 180 mg, 200 mg, 240 mg, 300 mg