Diltiazem works by relaxing the smooth muscle in the walls of arteries, resulting in them opening and allowing blood to flow more easily.[9] Additionally, it acts on the heart to prolong the period until it can beat again.[10] It does this by blocking the entry of calcium into the cells of the heart and blood vessels.[11] It is a class IV antiarrhythmic.[12]
Diltiazem was approved for medical use in the United States in 1982.[9] It is available as a generic medication.[9] In 2022, it was the 100th most commonly prescribed medication in the United States, with more than 6million prescriptions.[13][14] An extended release formulation is also available.[5][6][9]
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.[19]
It is also used as topical application for anal fissures because it promotes healing due to its vasodilatory property.[20]
Contraindications and precautions
In congestive heart failure, patients with reduced ventricular function may not be able to counteract the negative inotropic and chronotropic effects of diltiazem, the result being an even higher compromise of function.
With SA node or AV conduction disturbances, the 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.
A reflex sympathetic response, caused by the peripheral dilation of vessels and the resulting drop in blood pressure, works to counteract the negative inotropic, chronotropic and dromotropic effects of diltiazem. Undesirable effects include hypotension, bradycardia, dizziness, flushing, fatigue, headaches and edema.[21] Rare side effects are congestive heart failure, myocardial infarction, and hepatotoxicity.[22]
Drug interactions
Because of its inhibition of hepaticcytochromesCYP3A4, CYP2C9 and CYP2D6, there are a number of drug interactions.[23] Some of the more important interactions are listed below.
Beta-blockers
Intravenous diltiazem should be used with caution with beta-blockers because, while the combination is most potent at reducing heart rate, there are rare instances of dysrhythmia and AV node block.[24]
Quinidine
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.[25]
Fentanyl
Concurrent use of fentanyl with diltiazem, or any other CYP3A4 inhibitors, as these medications decrease the breakdown of fentanyl and thus increase its effects.[26]
Mechanism of action
Diltiazem, also known as (2S,3S)-3-acetoxy-5-[2-(dimethylamino)ethyl]-2,3-dihydro-2-(4-methoxyphenyl)-1,5-benzothiazepin-4(5H)-one hydrochlorid has a vasodilating activity attributed to the (2S,3S)-isomer.[27]
Diltiazem is a potent vasodilator, increasing blood flow and variably decreasing the heart rate via strong depression of A-V node conduction. It binds to the alpha-1 subunit of L-type calcium channels in a fashion somewhat similar to verapamil, another nondihydropyridine (non-DHP) calcium channel blocker.[28] Chemically, it is based upon a 1,4-thiazepinering, making it a benzothiazepine-type calcium channel blocker.
Diltiazem has negative inotropic, chronotropic, and dromotropic effects. This means diltiazem causes a decrease in heart muscle contractility – how strong the beat is, lowering of heart rate – due to slowing of the sinoatrial node, and a slowing of conduction through the atrioventricular node – increasing the time needed for each beat. Each of these effects results in reduced oxygen consumption by the heart, reducing angina, typically unstable angina, symptoms. These effects also reduce blood pressure by causing less blood to be pumped out.
Diltiazem is also being used in the treatment of anal fissures. It can be taken orally or applied topically with increased effectiveness.[40] When applied topically, it is made into a cream form using either petrolatum or Phlojel. Phlojel absorbs the diltiazem into the problem area better than the petrolatum base. It has good short-term success rates.[41][42]
^Claas SA, Glasser SP (May 2005). "Long-acting diltiazem HCl for the chronotherapeutic treatment of hypertension and chronic stable angina pectoris". Expert Opinion on Pharmacotherapy. 6 (5): 765–776. doi:10.1517/14656566.6.5.765. PMID15934903. S2CID39272285.
^Gabrielli A, Gallagher TJ, Caruso LJ, Bennett NT, Layon AJ (October 2001). "Diltiazem to treat sinus tachycardia in critically ill patients: a four-year experience". Critical Care Medicine. 29 (10): 1874–1879. doi:10.1097/00003246-200110000-00004. PMID11588443. S2CID25104288.
^Wattanasuwan N, Khan IA, Mehta NJ, Arora P, Singh N, Vasavada BC, et al. (February 2001). "Acute ventricular rate control in atrial fibrillation: IV combination of diltiazem and digoxin vs. IV diltiazem alone". Chest. 119 (2): 502–506. doi:10.1378/chest.119.2.502. PMID11171729.
^Griffin N, Acheson AG, Jonas M, Scholefield JH (October 2002). "The role of topical diltiazem in the treatment of chronic anal fissures that have failed glyceryl trinitrate therapy". Colorectal Disease. 4 (6): 430–435. doi:10.1046/j.1463-1318.2002.00376.x. PMID12790914. S2CID32959944.
^Ramoska EA, Spiller HA, Winter M, Borys D (February 1993). "A one-year evaluation of calcium channel blocker overdoses: toxicity and treatment". Annals of Emergency Medicine. 22 (2): 196–200. doi:10.1016/S0196-0644(05)80202-1. PMID8427431.
^Talreja O, Cassagnol M (2019). "Diltiazem". StatPearls. Treasure Island (FL): StatPearls Publishing. PMID30422532.
^Ohno Y, Hisaka A, Suzuki H (2007). "General framework for the quantitative prediction of CYP3A4-mediated oral drug interactions based on the AUC increase by coadministration of standard drugs". Clinical Pharmacokinetics. 46 (8): 681–696. doi:10.2165/00003088-200746080-00005. PMID17655375. S2CID41343222.
^Narimatsu A, Taira N (August 1976). "Effects of atrio-ventricular conduction of calcium-antagonistic coronary vasodilators, local anaesthetics and quinidine injected into the posterior and the anterior septal artery of the atrio-ventricular node preparation of the dog". Naunyn-Schmiedeberg's Archives of Pharmacology. 294 (2): 169–177. doi:10.1007/bf00507850. PMID1012337. S2CID21986119.
^O'Connor SE, Grosset A, Janiak P (1999). "The pharmacological basis and pathophysiological significance of the heart rate-lowering property of diltiazem". Fundamental & Clinical Pharmacology. 13 (2): 145–153. doi:10.1111/j.1472-8206.1999.tb00333.x. PMID10226758. S2CID20440286.
^Montastruc JL, Senard JM (April 1992). "[Calcium channel blockers and prevention of migraine]" [Calcium channel blockers and prevention of migraine]. Pathologie-Biologie (in French). 40 (4): 381–388. PMID1353873.
^Kim KE (February 1991). "Comparative clinical pharmacology of calcium channel blockers". American Family Physician. 43 (2): 583–588. PMID1990741.
^Paterna S, Martino SG, Campisi D, Cascio Ingurgio N, Marsala BA (July 1990). "[Evaluation of the effects of verapamil, flunarizine, diltiazem, nimodipine and placebo in the prevention of hemicrania. A double-blind randomized cross-over study]". La Clinica Terapeutica. 134 (2): 119–125. PMID2147612.
^Smith R, Schwartz A (May 1984). "Diltiazem prophylaxis in refractory migraine". The New England Journal of Medicine. 310 (20): 1327–1328. doi:10.1056/NEJM198405173102015. PMID6144044.
^Kishioka S, Ko MC, Woods JH (May 2000). "Diltiazem enhances the analgesic but not the respiratory depressant effects of morphine in rhesus monkeys". European Journal of Pharmacology. 397 (1): 85–92. doi:10.1016/S0014-2999(00)00248-X. PMID10844102.
^Verma V, Mediratta PK, Sharma KK (July 2001). "Potentiation of analgesia and reversal of tolerance to morphine by calcium channel blockers". Indian Journal of Experimental Biology. 39 (7): 636–642. PMID12019755.
^Jonas M, Neal KR, Abercrombie JF, Scholefield JH (August 2001). "A randomized trial of oral vs. topical diltiazem for chronic anal fissures". Diseases of the Colon and Rectum. 44 (8): 1074–1078. doi:10.1007/BF02234624. PMID11535842. S2CID40406260.
^Sajid MS, Rimple J, Cheek E, Baig MK (January 2008). "The efficacy of diltiazem and glyceryltrinitrate for the medical management of chronic anal fissure: a meta-analysis". International Journal of Colorectal Disease. 23 (1): 1–6. doi:10.1007/s00384-007-0384-x. PMID17846781. S2CID13015745.