Adult: Initially, 5-10 mg via slow inj over 2-3 minutes then 5 mg via inj after 5-10 minutes if needed. Child: ≤1 years 0.1-0.2 mg/kg; 1-15 years 0.1-0.3 mg/kg (Max: 5 mg). All doses to be given over at least 2 minutes, repeat after 30 min if needed.
Oral Angina pectoris
Adult: 120 mg tid or 80 mg tid in patients w/ angina of effort. As modified-release: Up to 480 mg daily.
Oral Supraventricular arrhythmias
Adult: 120-480 mg daily in 3-4 divided doses depending on patient's response and severity of the condition. Child: ≤2 yr 20 mg 2-3 times daily; >2 yr 40-120 mg 2-3 times daily, depending on age and response.
Oral Hypertension
Adult: Initially, 240 mg daily in 2-3 divided doses. Max: 480 mg daily. Child: ≤2 yr 20 mg 2-3 times daily; >2 yr 40-120 mg 2-3 times daily, depending on age and response.
Oral Secondary prophylaxis of myocardial infarction
Adult: Modified release: Initially, 360 mg daily in divided doses 1 wk after acute infarction.
Hepatic Impairment
Oral:
Severe: Reduce dose by up to 60-70%.
Administration
Should be taken with food.
Incompatibility
Y-site: Ampothericin B cholesteryl sulfate complex, nafcillin, ampicillin, oxacillin, albumin, pantoprazole, Na bicarbonate.
Contraindications
Cardiogenic shock, hypotension (systolic pressure <90 mmHg), marked bradycardia, uncompensated heart failure, 2nd- or 3rd-degree AV block (unless pacemaker is fitted), sick-sinus syndrome, severe ventricular dysfunction, atrial flutter or atrial fibrillation and accessory bypass tract (e.g. Wolff-Parkinson-White, Lown-Ganong-Levine syndromes).
Special Precautions
Patient w/ bradycardia or 1st-degree AV block, attenuated neuromuscular transmission, hypertrophic cardiomyopathy. Avoid abrupt withdrawal. Renal and hepatic impairment. Childn. Pregnancy and lactation.
Symptoms: Bradycardia, hypotension, conduction abnormalities, hyperglycaemia, hyperkalaemia, metabolic acidosis, renal dysfunction, seizures, impaired conduction, ECG changes, arrhythmias, shock, altered mental status, cardiac arrest. Management: Symptomatic and supportive treatment. Place patient Trendelenburg's position and admin IV fluids. Hypotension may be treated w/ IV Ca salts or vasopressor agent. Bradycardia or fixed 2nd- or 3rd-degree AV block may be treated w/ norepinephrine, IV atropine, isoproterenol, Ca salt or a temporary cardiac pacemaker. Consider endoscopy in cases of large overdoses.
Drug Interactions
May increase plasma level w/ CYP3A4 inhibitors (e.g. erythromycin, ritonavir), cimetidine. May decrease plasma level w/ CYP3A4 inducers (e.g. rifampicin), phenobarbital, sulfinpyrazone. Increased risk of bleeding w/ aspirin. May increase bradycardic and hypotensive effect w/ telithromycin. Increased AV blocking effect w/ clonidine. May increase plasma level of cardiac glycosides (e.g. digoxin, digitoxin), β-blockers (e.g. propranolol, metoprolol), α-blockers (e.g. terazosin, prazosin), immunosuppressants (e.g. sirolimus, ciclosporin, tacrolimus, everolimus), lipid lowering agents (e.g. lovastatin, simvastatin, atorvastatin), colchicines, quinidine, carbamazepine, imipramine, glibenclamide, doxorubicin, midazolam, buspirone, almotriptan, theophylline. May potentiate hypotensive effect w/ diuretics, antihypertensives, vasodilators. May increase neurotoxic effect of lithium.
Food Interaction
Increased plasma levels w/ grapefruit juice. May increase plasma level of alcohol. Decreased plasma levels w/ St John's wort.
Lab Interference
May cause false-positive result w/ urine detection of methadone.
Action
Description: Verapamil inhibits entry of Ca ions into the slow channels or select voltage-sensitive areas of vascular smooth muscle and myocardium during depolarisation. It relaxes coronary vascular smooth muscle and coronary vasodilation, increases myocardial oxygen delivery, and slows automaticity and AV node conduction. Onset: W/in 1-2 hr (oral); w/in 5 min (IV). Duration: 6-8 hr (oral); 10-20 min (IV). Pharmacokinetics: Absorption: Absorbed from the GI tract approx 90%. Bioavailability: 20-35% (oral). Time to peak plasma concentration: 1-2 hr (oral). Distribution: Crosses the placenta; enters breast milk. Volume of distribution: 3.89 L/kg. Plasma protein binding: Approx 90%. Metabolism: Extensively metabolised hepatically to at least 12 metabolites (e.g. norverapamil as primary metabolites). Excretion: Via urine (70% as metabolites, 3-4% as unchanged drug); faeces (16%). Terminal half-life: 2-8 hr; increases to 4.5-12 hr (after oral repeated dose).
Chemical Structure
Verapamil Source: National Center for Biotechnology Information. PubChem Database. Verapamil, CID=2520, https://pubchem.ncbi.nlm.nih.gov/compound/Verapamil (accessed on Jan. 23, 2020)
C08DA01 - verapamil ; Belongs to the class of phenylalkylamine derivative selective calcium-channel blockers with direct cardiac effects. Used in the treatment of cardiovascular diseases.
References
Anon. Verapamil. Lexicomp Online. Hudson, Ohio. Wolters Kluwer Clinical Drug Information, Inc. https://online.lexi.com. Accessed 21/11/2014.Buckingham R (ed). Verapamil Hydrochloride. Martindale: The Complete Drug Reference [online]. London. Pharmaceutical Press. https://www.medicinescomplete.com. Accessed 21/11/2014.Calan Tablets. U.S. FDA. https://www.fda.gov/. Accessed 21/11/2014.Isoptin SR Tablet, Coated (Abbott Laboratories). DailyMed. Source: U.S. National Library of Medicine. https://dailymed.nlm.nih.gov/dailymed/. Accessed 21/11/2014.McEvoy GK, Snow EK, Miller J et al (eds). Verapamil Hydrochloride. AHFS Drug Information (AHFS DI) [online]. American Society of Health-System Pharmacists (ASHP). https://www.medicinescomplete.com. Accessed 21/11/2014.Verelan Capsules and Verelan PM Extended-Release Capsules. U.S. FDA. https://www.fda.gov/. Accessed 21/11/2014.
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