Diltiazem

Question 1

Drug class?

Answer 1

Calcium channel blockers

Question 2

How does it work?

Answer 2

Interfere with inward displacement of calcium ions through slow channels of active cell membranes. Influence myocardial cells and the cells of vascular smooth muscle. Myocardial contractility may be reduced, formation and propagation of electrical impulses within the heart may be depressed and coronary or systemic vascular tone may be diminished.

Question 3

Indications?

Answer 3

Angina, hypertension, Raynaud’s phenomenon, supraventricular tachycardia, ischaemic neurological deficit following subarachnoid haemorrhage, prophylaxis for cluster headache.

Question 4

Contra-indications?

Answer 4

• Cardiovascular: shock, unstable angina, significant aortic stenosis, bradycardia, heart failure, etc.
• Avoidance of grapefruit juice with felodipine, lacidipine, lercanidipine, nicardipine, nifedipine, nimodipine and verapamil. This may affect metabolism.
• Sudden withdrawal of CCBs may exacerbate angina.

Question 5

Side-effects?

Answer 5

• Myocardial effects - Hypotension, heart failure.
• Conduction effects - Heart block, arrythmias.
• Vascular smooth muscle - flushing, oedmea, headaches, rashes.
• Others - constipation, rashes, gynaecomastia, photosensitivity.

Question 6

Interactions?

Answer 6

• Anti-arrhythmics: increased myocardial depression
• Beta blockers: increased risk of AV block/bradycardia
• Cyclosporin: increased plasma concentration
• Digoxin: increased plasma concentration
• Theophylline: increased effects