|File:Diltiazem Structural Formulae V.1.svg|
|Systematic (IUPAC) name|
|Biological half-life||3-4.5 hours|
Lactic (in lactiferous females)
|ATC code||C08DB01 (WHO)|
|Molar mass||414.519 g/mol[[Script error: No such module "String".]]|
|Script error: No such module "collapsible list".|
Diltiazem is a non-dihydropyridine (DHP) member of the group of drugs known as benzothiazepines, which are a class of calcium channel blockers, used in the treatment of hypertension, angina pectoris, and some types of arrhythmia. 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 very 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.
- Cartia XT
- Tiazac XC
- Tildiem in particular in Europe
- Angizem CD
- Dilcontin SR in India (Sustained Release)
Diltiazem is a potent vasodilator, increasing blood flow and variably decreasing the heart rate via strong depression of A-V node conduction. Its pharmacological activity is somewhat similar to verapamil.
Potent vasodilator of coronary vessels.
Vasodilator of peripheral vessels. This reduces peripheral resistance and afterload.
Negative inotropic effect. Diltiazem causes a modest decrease in heart muscle contractility and reduces myocardium oxygen consumption.
Negative chronotropic effect. Diltiazem causes a modest lowering of heart rate. This effect is due to slowing of the SA (sinoatrial) node. It results in reduced myocardium oxygen consumption.
Negative dromotropic effect. By slowing conduction through the AV (atrioventricular) node, diltiazem increases the time needed for each beat. This results in reduced myocardium oxygen consumption by the body.
Nontherapeutic effects and toxicities
Reflex sympathetic response. Caused by the peripheral dilation of vessels and the resulting drop in BP; the response works to counteract the negative inotropic, chronotropic and dromotropic effects of diltiazem. Undesirable effects of Diltiazem include hypotension, bradycardia, dizziness, flushing.
- Stable angina (exercise-induced) . Diltiazem increases coronary blood flow and decreases myocardial oxygen consumption, secondary to decreased peripheral resistance, heart rate, and contractility.
- Variant angina. Diltiazem 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.
Hypertension. 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.
Contraindications and precautions
CHF. Patients with reduced ventricular function may not be able to counteract the inotropic and chronotropic effects of diltiazem, the result being an even higher compromise of function.
SA node or AV conduction disturbances. Use of diltiazem should be avoided in patients with SA or AV nodal abnormalities, because of its negative chronotropic and dromotropic effects Low blood pressure. Patients with systolic blood pressures below 90 mm Hg should not be treated with diltiazem.
Wolff-Parkinson-White syndrome. Diltiazem may paradoxically increase ventricular rate in patients with WPW syndrome because of accessory conduction pathways.
Diltiazem is relatively contraindicated in the presence of sick sinus syndrome, atrioventricular node conduction disturbances, bradycardia, impaired left ventricle function, peripheral artery occlusive disease, chronic obstructive pulmonary disease, and Prinzmetal's angina.
Quinidine should not be used concurrently with calcium channel blockers because of reduced clearance of both drugs and potential pharmacodynamic effects at the SA and AV nodes.
Potential future indications
Diltiazem is prescribed off-label by doctors in the US for prophylaxis of cluster migraine. It works amazingly well in some patients. There is some research on diltiazem and other calcium channel antagonists in the treatment and prophylaxis of migraine.
Recent research has shown that diltiazem is able to reduce cocaine cravings in drug-addicted rats. This is believed to be due to the effects of calcium blockers on dopaminergic and glutamatergic signalling in the brain. Diltiazem also enhances the analgesic effect of morphine in animal tests, without increasing respiratory depression, and reduces the development of tolerance.
Diltiazem is also being used in the treatment of anal fissures. It can be taken orally or applied topically with equal effectiveness. When applied topically, it is made into a cream form using either vaseline or Phlogel. Phlogel absorbs the diltiazem into the problem area better than the vaseline base. It has good short term success rates.  Like all non-surgical treatments of anal fissure it does not address the long term problem of increased basal anal tone and does not decrease the subsequent recurrence rate that can vary between 40 to 60%.
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- Mills K, Ansah TA, Ali SF, Mukherjee S, Shockley DC. Augmented behavioral response and enhanced synaptosomal calcium transport induced by repeated cocaine administration are decreased by calcium channel blockers. Life Sciences. 2007 Jul 26;81(7):600-8. PMID 17689567
- Kishioka S, Ko MC, Woods JH. Diltiazem enhances the analgesic but not the respiratory depressant effects of morphine in rhesus monkeys. European Journal of Pharmacology. 2000 May 26;397(1):85-92. PMID 10844102
- Verma V, Mediratta PK, Sharma KK. Potentiation of analgesia and reversal of tolerance to morphine by calcium channel blockers. Indian Journal of Experimental Biology. 2001 Jul;39(7):636-42. PMID 12019755
- Nash GF, Kapoor K, Saeb-Parsy K, Kunanadam T, Dawson PM. The long-term results of diltiazem treatment for anal fissure. International Journal of Clinical Practice. 2006 Nov;60(11):1411-3. PMID 16911570
- Sajid MS, Rimple J, Cheek E, Baig MK. The efficacy of diltiazem and glyceryltrinitrate for the medical management of chronic anal fissure: a meta-analysis. International Journal of Colorectal Disease. 2008 Jan;23(1):1-6. PMID 17846781