Drug Class Description

Generic Name

Drug Description

Presentation

Indications

Adult Dosage

Route of administration

Oral.

Dosage may be taken with or without food, and should be swallowed whole and not chewed.

Angina

Adults:

The usual initial dose is 90 mg twice-daily. Dosage may be increased gradually to 120 mg twice-daily, or 180 mg twice-daily if required. Patients' responses may vary and dosage requirements can differ significantly between individual patients.

Elderly and patients with impaired renal or hepatic function:

In the elderly, dosage should commence at 60 mg diltiazem hydrochloride twice-daily and the dose carefully titrated as required.

Hypertension

Adults:

The usual dose is one ADIZEM-SR 120 mg tablet or capsule twice-daily. Patients may benefit by titrating from a lower total daily dose.

Child Dosage

The ADIZEM preparations are not recommended for children. Safety and efficacy in children has not been established.

In order to avoid confusion, it is suggested that patients, once titrated to an effective dose using either ADIZEM tablets or capsules, should remain on this treatment and should not be changed between different presentations.

Elderly Dosage

The starting dose should be 60 mg diltiazem hydrochloride twice-daily, increasing to one ADIZEM-SR 90 mg capsule twice-daily and then to one ADIZEM-SR 120 mg tablet or capsule twice-daily if clinically indicated.

Contra Indications

Pregnancy and in women of child-bearing capacity. Patients with bradycardia (less than 50 bpm), second or third degree heart block, sick sinus syndrome, decompensated cardiac failure, patients with left ventricular dysfunction following myocardial infarction. Concurrent use with dantrolene infusion because of the risk of ventricular fibrillation.

Special Precautions

The product should be used with caution in patients with reduced left ventricular function. Patients with mild bradycardia, first degree AV block or prolonged PR interval should be observed closely. Diltiazem is considered unsafe in patients with acute porphyria.

Interactions

Diltiazem is extensively metabolised by CYP3A4, and as a result serum levels of diltiazem may be:

•Increased by concomitant usage of CYP3A4 inhibitors such as H2 antagonists (e.g. cimetidine, ranitidine) and protease inhibitors (e.g. atazanavir, ritonavir)

Decreased by concomitant usage of CYP3A4 inducers such as barbiturates (phenobarbital, primidone), phenytoin and rifampicin.

Diltiazem is also an inhibitor of CYP3A4, and may therefore increase serum levels of CYP3A4 substrates such as benzodiazepines (especially midazolam and triazolam), carbamazepine, ciclosporin, cilostazol, ivabradine, statins (simvastatin, atorvastatin, lovastatin), sirolimus, tacrolimus and theophylline. Care should be exercised in patients taking these drugs. Concomitant use of diltiazem with cilostazol and ivabradine should be avoided.

There may be an additive effect (increased depression of cardiac conduction with risk of bradycardia and AV block) when diltiazem is prescribed with drugs which may induce bradycardia or other anti-arrhythmic drugs (e.g. amiodarone and beta blockers). Patients with pre-existing conduction defects should not receive the combination of diltiazem and beta-blockers.

Enhanced antihypertensive effect may occur with concomitant use of other antihypertensive drugs (e.g. beta-blockers, diuretics, ACE-inhibitors) or drugs that cause hypotension such as aldesleukin and antipsychotics. Concomitant use with alpha-blockers (e.g. prazosin) should be strictly monitored because of the possible synergistic hypotensive effect of this combination.

Diltiazem hydrochloride may cause small increases in plasma levels of digoxin, requiring careful monitoring of AV conduction.

Diltiazem may increase serum levels of phenytoin.

Diltiazem may increase bioavailability of tricyclic antidepressants.

Treatment with diltiazem has been continued without problem during anaesthesia, but the anaesthetist should be made aware of the treatment regimen.

The combination of alcohol and diltiazem may have an additive vasodilatory effect

Adverse Reactions

The adverse events listed below are classified by body system according to their incidence (common or uncommon). Common adverse events have an incidence of >1% and uncommon adverse events have an incidence of <1%.

Manufacturer

Drug Availability

Updated