Verapamil

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.
Hepatic impairment: Severe: Reduce dose by up to 60-70%.

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.
Hepatic impairment: Severe: Reduce dose by up to 60-70%.

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.
Hepatic impairment: Severe: Reduce dose by up to 60-70%.

Oral
Secondary prophylaxis of myocardial infarction
Adult: Modified release: Initially, 360 mg daily in divided doses 1 wk after acute infarction.
Hepatic impairment: Severe: Reduce dose by up to 60-70%.

Intravenous
Supraventricular arrhythmias
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.
Incompatibility: Y-site: Ampothericin B cholesteryl sulfate complex, nafcillin, ampicillin, oxacillin, albumin, pantoprazole, Na bicarbonate.

Should be taken with food.

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).

Patient w/ bradycardia or 1st-degree AV block, attenuated neuromuscular transmission, hypertrophic cardiomyopathy. Avoid abrupt withdrawal. Renal and hepatic impairment. Childn. Pregnancy and lactation. Monitoring Parameters Monitor BP, heart rate, ECG, LFTs (periodically).

AV block, bradycardia, worsening heart failure, transient asystole, hypotension, dizziness, flushing, fatigue, headache, dyspnoea, peripheral oedema, constipation, nausea, abnormal liver function, skin reactions, gingival hyperplasia, extrapyramidal symptoms. Rarely, gynaecomastia.
Potentially Fatal: Hepatotoxicity.

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.

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.

Increased plasma levels w/ grapefruit juice. May increase plasma level of alcohol. Decreased plasma levels w/ St John's wort.

May cause false-positive result w/ urine detection of methadone.

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).
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).

Intravenous: Store between 15-30°C. Protect from light. Oral: Store between 15-30°C. Protect from light.

Anti-Anginal Drugs / Calcium Antagonists

C08DA01 - verapamil ; Belongs to the class of phenylalkylamine derivative selective calcium-channel blockers with direct cardiac effects. Used in the treatment of cardiovascular diseases.