It is also an effective preventive medication for migraine. It is a class 3 anti-anginal drug, and a class IV antiarrhythmic. It is a common adulterant of cocaine seized in the UK, and has been found to reduce cocaine cravings in rats, indicating that it may prolong the "high" (see below). It incites minimal reflex sympathetic changes. It is based upon a 1,4-thiazepine ring.

Diltiazem is metabolized by and acts as an inhibitor of the CYP3A4 enzyme. It is also commonly used for rate control in Atrial fibrillation.

The drug is indicated for angina:

• Stable angina (exercise-induced) - diltiazem increases coronary blood flow and decreases myocardial oxygen consumption, secondary to decreased peripheral resistance, heart rate, and contractility.^[4][5]

• Variant angina - it is effective due to its direct effects on coronary dilation.

• Unstable angina (preinfarction, crescendo) - diltiazem may be particularly effective if the underlying mechanism is vasospasm.

For supraventricular tachycardias, diltiazem appears to be as effective as verapamil in treating re-entrant supraventricular tachycardia.^[6]

Atrial fibrillation^[7] or atrial flutter PSVT is another indication. The initial bolus should be 0.25mg/kg, intravenous (IV).

Because of its vasodilatory effects, diltiazem is useful for treating hypertension. Calcium channel blockers are well-tolerated, and especially effective in treating low-renin hypertension.^[8]