<p>Diltiazem is a benzothiazepine derivative with antihypertensive and vasodilating properties. Approved in 1982 by the FDA, it is a member of the non-dihydropyridine calcium channel blockers drug class. It works through various mechanisms of action, but it primarily works by inhibiting the calcium influx into cardiac and vascular smooth muscle during depolarization.<sup class="text-reference-group"><a class="reference-popover-link" data-content="CARDIZEM® LA (diltiazem hydrochloride) extended-release tablets - FDA Label" href="#reference-L10556">12</a></sup> Compared to dihydropyridine drugs, such as <a href="https://go.drugbank.com/drugs/DB01115">nifedipine</a>, that preferentially act on vascular smooth muscle and <a href="https://go.drugbank.com/drugs/DB00661">verapamil</a> that directly acts on the heart muscle, diltiazem displays an intermediate specificity to target both the cardiac and vascular smooth muscle.<sup class="text-reference-group"><a class="reference-popover-link" data-content="Rang, H. P. and Dale, M. M. (2012). Rang and Dale's Pharmacology  (7th ed.). Edinburgh: Elsevier/Churchill Livingstone. (ISBN 978-0-7020-3471-8)" href="#reference-T28">8</a></sup> Being a potent vasodilator, diltiazem is used clinically as an antihypertensive, anti-arrhythmic, and as an anti-anginal agent <sup class="text-reference-group"><a class="reference-popover-link" data-content="Diltiazem - StatPearls - NCBI Bookshelf" href="#reference-L6289">9</a></sup> for the management of cardiovascular conditions such as hypertension, chronic stable angina, atrial fibrillation, atrial flutter. Apart from its main FDA-approved indications, diltiazem has also been used for numerous off-label indications, such as anal fissures (in topical formulations), migraine prophylaxis, pulmonary hypertension, and rest-related cramps in the lower extremities.<sup class="text-reference-group"><a class="reference-popover-link" data-content="Diltiazem - StatPearls - NCBI Bookshelf" href="#reference-L6289">9</a></sup> Typically available in extended-release oral and intravenous formulations, diltiazem is marketed under various brand names with Cardizem and Tiazac being the most common ones.</p>