Formulary
Verapamil hydrochloride: Indications, Dosing, Side Effects and Interactions
For all calcium-channel blockers Calcium-channel blockers (less correctly called 'calcium-antagonists') interfere with the inward displacement of calcium ions...
MedNext Academy | 5 min read
Verapamil hydrochloride: Indications, Dosing, Side Effects and Interactions
For all calcium-channel blockers Calcium-channel blockers (less correctly called 'calcium-antagonists') interfere with the inward displacement of calcium ions...
Drug action
For all calcium-channel blockers Calcium-channel blockers (less correctly called 'calcium-antagonists') interfere with the inward displacement of calcium ions through the slow channels of active cell membranes. They influence the myocardial cells, the cells within the specialised conducting system of the heart, and the cells of vascular smooth muscle. Thus, myocardial contractility may be reduced, the formation and propagation of electrical impulses within the heart may be depressed, and coronary or systemic vascular tone may be diminished.
Indications and dose
**Treatment of supraventricular arrhythmias**
- **Adult** (By Mouth Using Immediate-Release Medicines): 40-120 mg 3 times a day.
- **Adult** (By Slow Intravenous Injection): 5-10 mg, to be given over 2 minutes, preferably with ECG monitoring.
- **Elderly** (By Slow Intravenous Injection): 5-10 mg, to be given over 3 minutes, preferably with ECG monitoring.
**Paroxysmal tachyarrhythmias**
- **Adult** (By Slow Intravenous Injection): Initially 5-10 mg, followed by 5 mg after 5-10 minutes if required, to be given over 2 minutes, preferably with ECG monitoring.
- **Elderly** (By Slow Intravenous Injection): Initially 5-10 mg, followed by 5 mg after 5-10 minutes if required, to be given over 3 minutes, preferably with ECG monitoring.
**Angina**
- **Adult** (By Mouth): 240 mg twice daily, may sometimes be reduced to once daily.
**Hypertension**
- **Adult** (By Mouth): 240 mg daily, increased if necessary to 240 mg twice daily.
**Prophylaxis of cluster headache (initiated under specialist supervision)**
- **Adult** (By Mouth Using Immediate-Release Medicines): 240-960 mg daily in 3-4 divided doses.
**Hypertension (in patients new to verapamil)**
- **Adult** (By Mouth): Initially 120 mg daily, increased if necessary up to 480 mg daily, doses above 240 mg daily as 2 divided doses.
**Prophylaxis after myocardial infarction where beta-blockers not appropriate**
- **Adult** (By Mouth): 360 mg daily in divided doses, started at least 1 week after infarction, given as either 240 mg in the morning and 120 mg in the evening or 120 mg 3 times daily.
**Mild to moderate hypertension**
- **Adult** (By Mouth): 240 mg daily, increased if necessary to 240 mg twice daily.
**Treatment of supraventricular arrhythmias for verapamil hydrochloride**
- **Child 1-17 years (administered on expert advice)** (By slow intravenous injection): 100-300 micrograms/kg (max. per dose 5 mg) for 1 dose, to be given over 2-3 minutes (with ECG and blood-pressure monitoring), dose can be repeated after 30 minutes if necessary.
**Hypertension for verapamil hydrochloride**
- **Child 12-23 months (administered on expert advice)** (By mouth using immediate-release medicines): 20 mg 2-3 times a day.
- **Child 2-17 years (administered on expert advice)** (By mouth using immediate-release medicines): 40-120 mg 2-3 times a day.
**Prophylaxis of supraventricular arrhythmias (administered on expert advice) for verapamil hydrochloride**
- **Child 12-23 months** (By mouth using immediate-release medicines): 20 mg 2-3 times a day.
- **Child 2-17 years** (By mouth using immediate-release medicines): 40-120 mg 2-3 times a day.
Cautions
For all calcium-channel blockers Elderly Cautions, further information Elderly Screening Tool of Older Persons' potentially inappropriate Prescriptions (STOPP) criteria to aid medication reviews (see Prescribing in the elderly for information): potentially inappropriate with persistent postural hypotension i.e. recurrent drop in systolic blood pressure 20 mmHg (risk of syncope and falls). Cautions For verapamil hydrochloride Acute phase of myocardial infarction (avoid if bradycardia, hypotension, left ventricular failure); first-degree AV block; neuromuscular disorders Cautions, further information Elderly Screening Tool of Older Persons' potentially inappropriate Prescriptions (STOPP) criteria to aid medication reviews (see Prescribing in the elderly for information): potentially inappropriate in patients with NYHA Class III or IV heart failure (contra-indicated in heart failure with reduced ejection fraction; may worsen heart failure).
Contraindications
Acute porphyrias ; atrial flutter or fibrillation associated with accessory conducting pathways (e.g. Wolff-Parkinson-White-syndrome); bradycardia; cardiogenic shock; heart failure (with reduced ejection fraction); history of significantly impaired left ventricular function (even if controlled by therapy); hypotension; second- and third-degree AV block; sick sinus syndrome; sino-atrial block
Side effects
For all calcium-channel blockers Common or very common Abdominal pain; dizziness; drowsiness; fatigue; flushing; headache; hypotension; nausea; palpitations; peripheral oedema; skin reactions; tachycardia; vomiting Uncommon Angioedema; depression; erectile dysfunction; gingival hyperplasia; myalgia; paraesthesia; syncope Overdose Features of calcium-channel blocker poisoning include nausea, vomiting, dizziness, agitation, confusion, and coma in severe poisoning. Metabolic acidosis and hyperglycaemia may occur. In overdose, the dihydropyridine calcium-channel blockers cause severe hypotension secondary to profound peripheral vasodilatation. For details on the management of poisoning, see Calcium-channel blockers, under Emergency treatment of poisoning. Side-effects For verapamil hydrochloride General side-effects: Frequency not known Atrioventricular block; extrapyramidal symptoms; gynaecomastia; Stevens-Johnson syndrome; vertigo Specific side-effects: Common or very common With intravenous use Bradycardia Frequency not known With intravenous use Cardiac arrest; hepatic impairment; hyperhidrosis; myocardial contractility decreased; nervousness; seizure With oral use Abdominal discomfort; alopecia; arrhythmias; arthralgia; constipation; erythromelalgia; galactorrhoea; heart failure; ileus; muscle weakness; tinnitus; tremor Overdose In overdose, verapamil has a profound cardiac depressant effect causing hypotension and arrhythmias, including complete heart block and asystole.
Interactions
**Severe interactions:**
- In rare instances, including when patients with severe cardiomyopathy, congestive heart failure or recent myocardial infarction were given intravenous beta-adrenergic blocking agents or disopyramide...
- Although there is no direct in vivo clinical evidence, there is strong potential for verapamil to significantly affect atorvastatin pharmacokinetics in a similar manner to s imvastatin or lovastatin.
**Other interactions (42):**
- Verapamil has been shown to be an inhibitor of CYP3A4 enzymes and P-glycoprotein (P-gp).
- The following are potential drug interactions due to pharmacokinetic reasons: Acetylsalicylic acid Concomitant use of verapamil with aspirin may increase the risk of bleeding.
- Alcohol Increase in blood alcohol has been reported.
- Alpha blockers Verapamil may increase the plasma concentrations of prazosin and terazosin which may have an additive hypotensive effect.
- Antiarrhythmics Verapamil may slightly decrease the plasma clearance of flecainide whereas flecainide has no effect on the verapamil plasma clearance.
- Verapamil may increase the plasma concentrations of quinidine .
Pregnancy
May reduce uterine blood flow with fetal hypoxia. Manufacturer advises avoid in first trimester unless absolutely necessary. May inhibit labour.
Breast feeding
Amount too small to be harmful.
Hepatic impairment
For all calcium-channel blockers In general, manufacturers advise caution (risk of increased exposure). Hepatic impairment For verapamil hydrochloride Dose adjustments With oral use: Manufacturer advises dose reduction.
Medicinal forms
Solution,Tablet,Tablet,Solution,Solution
Clinical governance
**Author:** MedNext Clinical Team. **Clinical reviewer:** Dr Shameer Deen, MBBS, MS, MRCS. **Sources:** BNF, Indian Pharmacopoeia, CIMS India. **Correction:** Report errors at support@mednext.academy.
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