Disclaimer: This information is for educational purposes and is not a substitute for professional medical advice. Isoptin (Verapamil) is a potent cardiovascular medication with significant side effects and drug interactions. Use only as prescribed and monitored by a doctor.
Isoptin (Verapamil): A Guide to the Calcium Channel Blocker
Manufacturer: The oral forms (tablets) are produced in Egypt by Kahira Pharm. & Chem. Ind. Co. under license from Abbott Laboratories. The injection form is imported directly from Abbott Laboratories.
Category: Non-Dihydropyridine Calcium Channel Blocker
Active Ingredient: Verapamil Hydrochloride
Available Forms:
- Tablets (80 mg): Immediate-Release, manufactured by Kahira.
- SR Tablets (240 mg): Sustained-Release (also known as "Retard"), manufactured by Kahira.
- IV Injection (5 mg / 2 ml): Ampoules for intravenous use, imported from Abbott Laboratories (not manufactured by Kahira).
Summary
Isoptin (Verapamil) is a cardiovascular drug known as a calcium channel blocker. Unlike some other drugs in its class that primarily affect blood vessels, Isoptin has significant effects on both the heart muscle and the heart's electrical conduction system. It is used to treat hypertension (high blood pressure), angina (chest pain from coronary insufficiency), and certain types of cardiac arrhythmias (irregular heartbeats).
Mechanism of Action: How Isoptin Works
Isoptin works by blocking the entry of calcium ions into the muscle cells of the heart and blood vessel walls. Calcium is essential for muscle contraction. By reducing calcium influx, Isoptin causes:
- Vasodilation: The smooth muscle in the walls of arteries relaxes, causing them to widen. This lowers peripheral vascular resistance, which in turn lowers blood pressure.
- Negative Chronotropic Effect: It slows down the heart's natural pacemaker (the SA node) and delays electrical signal conduction through the AV node. This results in a slower heart rate, which is useful for treating tachyarrhythmias (fast heart rhythms).
- Negative Inotropic Effect: It reduces the force of the heart's contractions, which decreases the oxygen demand of the heart muscle, helping to relieve angina.
Therapeutic Indications: When is Isoptin Used?
The specific formulation of Isoptin used depends on the condition being treated:
- Hypertension: Primarily treated with Isoptin SR 240 mg tablets for convenient once or twice-daily dosing.
- Angina Pectoris (Chronic Stable & Vasospastic): Typically treated with Isoptin 80 mg tablets, taken 3-4 times a day.
- Cardiac Arrhythmias:
- Chronic control of supraventricular tachycardias is managed with Isoptin 80 mg tablets.
- Acute termination of supraventricular tachycardias in a hospital setting is done with Isoptin 5 mg IV injection.
- Secondary Prevention after Myocardial Infarction: Isoptin SR 240 mg tablets may be used for this purpose.
Dosage and Administration
Dosage must be individualized by a physician. Tablets should be swallowed whole, preferably with or shortly after meals.
- Hypertension (SR 240 mg): Usually one tablet in the morning. Can be increased to a maximum of two tablets daily.
- Angina/Arrhythmia (80 mg): One tablet 3-4 times daily.
- IV Injection: Administered by a healthcare professional in an emergency setting.
Important: The dose must be carefully adjusted in patients with impaired liver function, as the drug's metabolism is reduced.
Key Contraindications, Warnings, and Side Effects
- Contraindications: Severe hypotension, cardiovascular shock, severe heart failure, and certain severe conduction disorders (e.g., 2nd or 3rd-degree AV block, sick sinus syndrome).
- Key Side Effects:
- Constipation: This is the most common side effect and can be significant.
- Cardiovascular: Bradycardia (slow heart rate), hypotension (low blood pressure), dizziness, flushing, and ankle edema.
- Other: Headache, fatigue, and nausea are also reported.
- Critical Drug Interactions:
- Beta-Blockers: Combining Isoptin with beta-blockers (like propranolol, metoprolol) can lead to severe bradycardia, heart block, and heart failure. IV beta-blockers must not be given to patients on Isoptin.
- Digoxin: Isoptin can significantly increase digoxin levels in the blood, raising the risk of digoxin toxicity. Dosage adjustment and monitoring are essential.
- Other Drugs: Isoptin can also increase the levels of carbamazepine, cyclosporin, and theophylline. Its own levels can be reduced by drugs like rifampicin and phenobarbital.
Frequently Asked Questions (FAQ)
- What is the main difference between Isoptin and Isoptin SR?
- Isoptin (80 mg) is an immediate-release tablet that works quickly but for a shorter duration, requiring multiple daily doses. It's mainly for angina and arrhythmias. Isoptin SR (240 mg) is a sustained-release tablet that releases the drug slowly over the day, allowing for once-daily dosing, making it ideal for managing hypertension.
- Why is constipation such a common side effect?
- Verapamil blocks calcium channels not only in the heart and blood vessels but also in the smooth muscle of the gastrointestinal tract. This relaxes the intestinal muscles, slowing down motility and leading to constipation.
- Can I drink grapefruit juice while taking Isoptin?
- It is generally advised to avoid grapefruit juice. Grapefruit inhibits the same enzyme (CYP3A4) that metabolizes Verapamil. Drinking it can significantly increase the levels of Isoptin in your blood, raising the risk of side effects like low blood pressure and slow heart rate.
Sources
- Verapamil Professional Information - Drugs.com
- Verapamil - StatPearls, NCBI
- Official Product Leaflets for Isoptin and Isoptin SR.
Comments
Post a Comment