Verapamil Pharmacology


About Verapamil
Calcium channel blocker, phenylalkylamine derivative, Class IV Antiarrhythmic, antihypertensive.
Mechanism of Action of Verapamil
Verapamil is a phenylalkylamine; Ca channel blocker. It exerts it`s antianginal, antihypertensive, antiarrythmic actions through blocking the influx of Ca ions through voltage gated L-type Ca channels to the peripheral vascular smooth muscle cells, Coronary smooth muscle cells and to the myocardial cells. Thus causes dilatation of vascular endothelium, decrease peripheral resistance, and decrease BP in hypertensive individuals.
It increase exercise tolerance and reduce myocardial oxygen demand in angina patients. It acts as a coronary artery dilator inhibits coronary artery spasm and improves coronary blood flow and myocardial oxygen supply. It decreases after load and cardiac work.
It prevents conduction and development of action potentials in heart. It suppresses
automaticity. It interferes with depolarization and decreases SA node automaticity and ventricular automaticity. It prolongs AV nodal and bypass tract effective refractory period and increases PR interval. It has negative ionotropic and chronotropic effect but cardiac out put is maintained by reflex sympathetic stimulation and decrease in aortic impedance. It markedly relaxes arterioles and milder effects on veins. It does not compromise haemodynamics and cerebral and renal perfusion.
Migraine: It is used in migraine by reducing intracellular Ca +2 overload due to brain hypoxia and other causes

Pharmacokinets of Verapamil
Absorption: Well absorbed orally, bioavailability is reduced due to first pass metabolism.
Distribution: Widely distributed in a protein bound form.
Metabolism: Metabolized in liver, and there is active metabolite.
Excretion: Excreted through urine.
Onset of Action for Verapamil
I.V.:2 to 3 minutes
Oral: Half an hour
Duration of Action for Verapamil
8 to 12 hours
Half Life of Verapamil
4 to 6 hours
Side Effects of Verapamil
1. Bradycardia
2. Worsens heart failure
3. Transient asystole
4. Constipation
5. Hypotension
6. Palpitation
7. Flushing
8. Nausea
9. Edema
10. A-V block
11. Headache
12. Dizziness
13. Vasodilatation
14. Rashes
15. Nervousness
16. Vertigo
17. Paraesthesia
18. Abnormal liver functioning

Contra-indications of Verapamil
1. Heart failure
2. 2nd and 3rd degree Heart block
3. Sick sinus syndrome
4. Hypersensitivity to the drug
5. Hypotension
6. Cardiogenic shock
7. Bradycardia
8. In digitalis toxicity
9. Wolff Parkinson white syndrome.(atrial fibrillation with pre excitation)
10. Tachyarrhythmias where QRS complex is wide unless a supraventricular origin is established

Special Precautions while taking Verapamil
1. Bradycardia
2. Hypotension
3. Hypertrophic cardiomyopathy
4. Conduction disturbance
5. Impaired left ventricular function
6. Congestive heart failure
7. First degree heart block
8. Hepatic impairment
9. Renal impairment
10.Use cautiously along with other antihypertensive drugs,
11.Use with caution along with digitalis and other antiarrhythmic drugs
12.Slowly withdraw the drug with caution,
13.In thrombocytopenia and defective platelet function.
Pregnancy Related Information
Use with caution
Old Age Related Information
Use with caution
Breast Feeding Related Information
Children Related Information
Use with caution
Indications for Verapamil
1. Paroxysmal supraventricular tachycardia
2. Atrial fibrillation
3. Atrial flutter
4. Angina
5. Hypertension
6. Hypertrophic cardiomyopathy
7. Coronary insufficiency
8. Myocardial infarction
9. Nocturnal leg cramps
10. Migraine prophylaxis
Interactions for Verapamil
Histamine H2 antagonists: May enhance bioavailability.
B-Blockers: Though advantageous in some, concomitant use results in increased adverse effects like bradycardia and conduction disturbances.
Digitalis Glycosides: Increased serum digoxin levels.
Magnesium Sulfate: With parenteral magnesium sulfate neuromuscular blockade and hypotension may occur.
Theophyllines: Efficacy of theophylline increased.
Quinidine: Hypotension, bradycardia, ventricular tachycardia, AV block and pulmonary oedema may occur.
Fentanyl: Severe hypotension or increased fluid requirements.
Barbiturates: Bioavailability of verapamil may be decreased.
Rifampicin: Loss of efficacy of oral verapamil.
Vitamin D: Efficacy of verapamil may be reduced.
Carbamazepine: Serum level of carbamazepine may be increased.
Cyclosporine: Increased cryclosporine levels with possible toxity. However,verapamil may be nephroprotective if given before cyclosporine.
Lithium: Altered response.
Non-depolarising muscle relaxants: Muscle relaxant effects may be increased, respiratory depression may be prolonged.
Prazosin: May increase sensitivity to prazosin induced postural hypotension.
Typical Dosage for Verapamil
Oral: 120 to 320mg/day in 3 to 4 divided doses.
Maximum dose: 480mg/day
I.V.: Starts with 5mg. Repeat the therapy with same dose after 5 to 10minutes depending up on the patient`s response.
On recurrence infuse 5 to 10mg/hour gradually up to 100mg if required depending up on the patient`s response
Children (below 6years):
Oral: 80 to 120mg in 2 to 3 divided doses
6 to 12 years: 80 to 320mg in 2 to 3 divided doses
Maximum dose: 360mg/day
Parenteral: Up to 1.5mg/kg/day and Starts with following doses
1 to 5 years: 2 to 3mg
6 to 14 years: 2.5 to 5mg
Paroxysmal supraventricular tachycardia: 5mg I.V. over 2 to 3 minutes. Prevents recurrence with 60 to 120mg orally 8th hourly. Gradually increases the dose if required based on patient`s response.

Atrial fibrillation and atrial flutter: 40 to 80mg 8th hourly orally. Gradually increases the dose if required based on patient`s response up to 320mg.
Angina: 80 to 120mg 8th hourly. Gradually increases the dose if required based on patient`s response.
Hypertension: 80mg 8th hourly. Gradually increases the dose if required based on patient`s response.

Schedule of Verapamil
Storage Requirements for Verapamil
Store in a cool dry place below 25 degree C. Protects from light.
Effects of Missed Dosage of Verapamil
Take the missed dose as soon as noticed and if it is the time for next dose then skip the missed dose. Continue the regular schedule. Do not double the dose.
Effects of Overdose of Verapamil
Treatment is supportive and symptomatic. Remove drug from the stomach by gastric lavage. Reduce absorption by administering activated charcoal Monitor &support cardiac and respiratory functions. Measure the BP. Give cardiovascular support by elevating the limbs and maintaining fluid balance. Administer vasopressers like nor epinephrine if required to treat hypotension. Treat Bradycardia with atropine. Administer isoproterenol with caution if required. Treat heart block with cardiac pacing. Treat cardiac failure with ionotropic agents such as isoproterenol, dopamine, dobutamine etc and diuretics.

Home Delivery for Verapamil in Your City

Medicine India is just a publishing medium for medicine related information and does not provide services or sales of medicines including verapamil.

However, we do publish a comprehensive directory of Pharmacies, Chemists and Druggists in cities all over India. You can use this directory to find the medicine stores in your city (or area) that provide home delivery services for verapamil and other medicines and health products. Home delivery services for verapamil may be free or they may cost you depending on the pharmacy and the minimum order requirements. It would be best to get this clarified while placing the order.

Please be aware that you should take verapamil only if a doctor has recommended or prescribed it. Some or all pharmacies who provide a home delivery service for medicines might insist on a prescription for verapamil before they complete the sale. You can get this information while placing the order for verapamil with the pharmacy.

Verapamil is a generic medicine name and there are several brands available for it. Some of the brands for verapamil might be better known than verapamil itself. If the pharmacy that's willing to deliver medicines to your home doesn't have verapamil in stock, you can ask for one of the branded alternatives for verapamil.