BRAND NAMES
 MECHANISM OF ACTION
Unlike dihydropyridines calcium-channel blockers with predominant selectivity on calcium channels of vascular smooth muscle cells than on cardiac muscle cells, Diltiazem is a benzothiazepine calcium channel blocker which inhibits the influx of extracellular calcium across both the myocardial and vascular smooth muscle cell membranes
The resultant inhibition of the contractile processes of the myocardial smooth muscle cells leads to a modest decrease in heart muscle contractility and heart rate and a reduction of myocardial oxygen consumption (Antianginal action)
The inhibition of the contractile processes of the vascular smooth muscle cells leads to a dilation of the coronary arteries with an improved oxygen delivery to the myocardial tissue (antianginal action), and a dilation of peripheral arteries with a decrease in total peripheral resistance and systemic blood pressure (antihypertensive action)
The magnitude of blood pressure reduction is related to the degree of hypertension; thus, hypertensive individuals experience an antihypertensive effect, whereas there is only a modest fall in blood pressure in normotensive individuals.
- Treatment of hypertension
- Management of chronic stable angina pectoris (chest pain or discomfort that usually occurs with activity or stress, due to poor blood flow through coronary vessels to the heart muscle)
- Management of Prinzmetal's variant angina (a vasospastic angina consisting of cardiac chest pain at rest, caused by contraction of the coronary vessels )
- Paroxysmal supraventricular tachycardia (PSVT) (An abnormally fast heart beat)
- Angina: Initially 60 mg twice daily. this dose may be increased to 120 mg twice daily. The maximum recommended dose is 360 mg daily.
- Hypertension: The initial dose should be one 120 mg retard tablet daily, administered preferably before meals, and at bedtime. Maximum antihypertensive effect is usually observed at 14 days of chronic therapy; therefore, dosage adjustments should be scheduled accordingly. The usual dosage range is 240 to 360 mg/day.
- Hypersensitivity to Diltiazem
- Sick sinus syndrome except in the presence of a functioning ventricular pacemaker
- Second or third-degree AV block except in the presence of a functioning ventricular pacemaker.
- Hypotension (less than 90 mm Hg systolic)
- Severe congestive heart failure or bradycardia (Less than 50 beats per minute)
- Acute myocardial infarction
- Left ventricular failure with pulmonary stasis
- Pregnancy and lactation
- Alpha-antagonists: Concomitant treatment with Alpha-antagonists may produce or aggravate hypotension.
- Beta-blockers: Diltiazem may cause rhythm distubances (Bradycardia, marked prolongation of atrioventricular conduction and heart failure). Caution is advised if combination therapy is considered. Patients with depressed left ventricular function and conduction system disease should not use this combination.
- Nitrate derivatives: Increased hypotensive effects and faintness. Nitrate derivative (e.g. nitroglycerin dosage should be gradually increased.
- Lithium carbonate: Risk of increase in lithium-induced neurotoxicity
- Amiodarone, Digoxin: Increased risk of bradycardia. caution isrequired when these are combined with diltiazem, particularly in elderly subject and when high doses are used.
- Antiarrhythmics: Since diltiazem has antiarrhythmic properties, its concomitant prescription with other antiarrhythmic is no recommended (additive risk of increased cardiac adverse effects). This combination should only be used under close clinical and ECG monitoring.
- Carbamazepine: Increase in circulating carbamazepine. Carbamazepine the dose should be adjusted
- Ciclosporin: Increase in circulating ciclosporin levels. Ciclosporin dose should be reduced.
- Ranitidine: Increase in plasma diltiazem concentrations. An adjustment in diltiazem daily dose may be necessary.
- Diltiazem is metabolized in humans by CYP3A4
- CYP3A4 inhibitors : CYP3A4 inhibitors like Ketoconazole, Itraconazole, Nefazodone, erythromycin, Clarithromycin, Isoniazid, fluvoxamine, Fluoxetine, HIV protease inhibitors (e.g. ritonavir, indinavir, nelfinavir), reverse transcriptase inhibitors (e.g. delavirdine) and Grapefruit juice can potentiate its effect
- CYP3A4 inducers (e.g. carbamazepine, efavirenz, St John’s wort, nevirapine, phenobarbitol, phenytoin, primidone, rifabutin, rifampicin) are expected to decrease Diltiazem concentrations.
- Diltiazem is also a CYP3A4 isoform inhibitor:
- Diltiazem significantly increases plasma concentrations of midazolam and triazolam (short-acting benzodiazepine metabolized by the CYP3A4) and prolongs their half-life
- The risk of myopathy and rhabdomyolysis due to statins metabolised by CYP3A4 (e.g. atorvastatin, fluvastatin, and simvastatin) may be increased with concomitant use o diltiazem. when possible, it is recommended to use a statin not metabolised by CYP3A4 (e.g. pravastatin)
 PREGNANCY AND LACTATION
- Pregnancy Category C (US). There are no well-controlled studies of the use of diltiazem in pregnant women. There is the potential to produce fetal hypoxia associated with maternal hypotension therefore, diltiazem should only be used if the potential benefit justifies the potential risk to the fetus.
- Lactation: Diltiazem is excreted in human milk and breast milk concentrations may approximate serum levels. Since the safety and effectiveness of diltiazem in infants and children has not been established an alternative method of infant feeding should be instituted if use of diltiazem is deemed essential.
 SIDE EFFECTS
Common adverse effects include: headache, facial redness (flushing), peripheral edema, dizziness, constipation, dyspepsia, gastric pain, nausea, erythema, fatigue and atrioventricular block (a potentially serious adverse effect, the risk is increased by concurrent use of a beta-blocker).
Mild to moderate elevation of alkaline phosphatase and transaminases occurs rarely
 RELATED LINKS
|ACE inhibitors||Benazepril (Lotensin) • Captopril (Capoten) • Cilazapril • Delapril • Enalapril (Renitec, Vasotec) • Fosinopril (Monopril) • Lisinopril (Prinivil, Zestril) • Moexipril (Univasc) • Perindopril (Aceon) • Quinapril (Accupril) • Ramipril (Altace, Triatec) • Trandolapril (Mavik) • Zofenopril (Bifril, Zopranol)|
|Angiotensin II receptor antagonist||Azilsartan (Edarbi) • Candesartan (Atacand) • Eprosartan (Teveten) • Irbesartan (Aprovel, Avapro, Karvea) • Losartan (Cozaar) • Olmesartan (Benicar, Olmetec) • Telmisartan (Micadis) • Valsartan (Diovan, Tareg)|
|Renin inhibitors||Aliskiren (Rasilez, Tekturna)|
|Alpha-1 blockers||Doxazosin (Cardura) • Prazosin (Minipress) • Terazosin (Hytrin)|
|Alpha-2 agonists (centrally acting)||Clonidine (Oral route) • Clonidine (Transdermal) (Catapresan) • Guanfacine (Tenex) • Methyldopa (Aldomet)|
|Calcium channel blockers||Dihydropyridines||Amlodipine (Norvasc) • Barnidipine (Vasexten) • Felodipine (Plendil) • Isradipine (Dynacirc) • Lacidipine (Lacipil, Motens) • Lercanidipine (Zanidip) • Manidipine • Nicardipine • Nifedipine (Adalat) • Nisoldipine • Nitrendipine|
|Benzothiazepine||Diltiazem (Cardizem, Taztia XT, Tiazac, Tildiem)|
|Phenylalkylamine||Gallopamil • Verapamil (Calan)|
|Beta blockers||Beta1 selective (cardioselective)||Acebutolol (Sectral) • Atenolol (Tenormin) • Betaxolol (Kerlon) • Bisoprolol (Concor) • Celiprolol (Cordiax) • Metoprolol (Betaloc, Lopressor, Toprol-XL) • Nebivolol (Bystolic, Lobivon, Nebilox)|
|Nonselective (Beta1 and Beta2 blockers)||Oxprenolol (Trasitensin) • Propranolol (Inderal) • Timolol (Blocadren)|
|Nonselective (Beta1, Beta2 and Alpha1 blockers)||Carvedilol (Dilatrend) • Labetalol (Trandate)|
|Beta blocker with intrinsic sympathomimetic activity (ISA)||Acebutolol (Sectral) • Celiprolol (Cordiax)|
|Lipophilic Beta blockers||Propranolol (Inderal) • Metoprolol (Betaloc, Lopressor, Toprol-XL) • Oxprenolol (Trasitensin)|
|Diuretics||Carbonic anhydrase inhibitors||Acetazolamide (Diamox)|
|Loop diuretics||Bumetanide • Etacrynic acid • Furosemide (Lasix) • Piretanide • Torasemide (Demadex)|
|Thiazide diuretics||Chlorothiazide (Diuril) • Hydrochlorothiazide (Esidrex)|
|Thiazide-like diuretics||Chlortalidone (Hygroton) • Indapamide (Lozol, Lozide) • Metolazone|
|Potassium-sparing diuretics|| Epithelial sodium channel blockers: Amiloride (Midamor) • Triamterene (Dyrenium) |
Aldosterone receptor antagonists: Potassium canrenoate • Eplerenone (Inspra) • Spironolactone (Aldactone)
|Combination therapy||Amiloride/Hydrochlorothiazide (Moduretic) • Spironolactone/Hydrochlorothiazide (Aldactazide)|