Verapamil
Drug class: Calcium-channel Blocker, CCB
Verapamil (ISOPTIN) （中文：維拉帕米） is a phenylalkylamine calcium-channel blocker. It is used for:
a. Prevention and long-term treatment of angina.
b. Treatment of mild to moderate hypertension.
c. Treatment of supraventricular arrhythmias
Pronunciation[edit]
Verapamil 40mg[edit]
| Generic Name: | Verapamil |
|---|---|
| Class: | Cardiovascular Drug |
| Subclass: | Calcium-channel Blocker, CCB |
| Legal Classification: | P1S1S3 |
Drug Names[edit]
| Generic Name 藥物化學名稱 | HA Code 藥物代碼 | Legal Classification法律藥物分類 |
|---|---|---|
| Verapamil HCL Tablet 40mg | VERA01 | P1S1S3 |
Mechanism of Action[edit]
Verapamil is a peripheral and coronary vasodilator. It also slows conduction through the AV node, and thus slows the increased ventricular response rate that occurs in atrial fibrillation and flutter. Verapamil works by lowering your blood pressure and makes it easier for your heart to pump blood around your body. In angina, verapamil works by improving the blood and oxygen supply to your heart. Angina is chest pain that comes on when not enough blood gets to the muscles of the heart. This usually happens because the arteries going to the heart become hardened and narrowed.
Route of Administration[edit]
Verapamil may be given intravenously or orally, as the hydrochloride; doses are expressed in terms of verapamil hydrochloride.
Dosage[edit]
Your dose of diltiazem depends on why you need the medicine and what kind your doctor has prescribed. It is important to keep taking the same brand of diltiazem once you have started.
Agina
- BY MOUTH
- Adult: 80 – 120 mg 3 times a day
Hypertension
- BY MOUTH
- Adult: initially 120 mg twice daily increasing to 160 mg twice daily where necessary. In some cases, doses of up to 480 mg daily, in divided doses, have been used.
Supraventricular Arrhythmias
- BY MOUTH
- Adult:40 – 120 mg 3 times daily.
Side Effects[edit]
The following definitions of frequencies are used:
Very common ≥ 1/10
Common ≥ 1/100 to < 1/10
Uncommon ≥ 1/1,000 to < 1/100
Rare ≥ 1/10,000 to < 1/1,000
Very rare < 1/10,000
| System Organ Class | Frequency | Adverse reactions |
|---|---|---|
| Nervous system disorder | Common | Headache, dizziness |
| Cardiac disorders | Common | Atrioventricular block, bradycardia |
| Vascular disorders | Common | Flushing, orthostatic hypotension |
| Gastro-intestinal disorders | Common | Gastric pain, dyspepsia, nausea, constipation |
| General disorders | Common | Peripheral oedema, notably of ankles |
Pharmacokinetics[edit]
Absorption
Verapamil is 90% absorbed from the gastrointestinal tract after oral doses, but undergoes extensive first-pass hepatic metabolism resulting in a bioavailability of about 20%.
Peak plasma concentrations occur about 1 to 2 hours after an oral dose.
Distribution
Verapamil is about 90% bound to plasma proteins. It is distributed into breast milk.
Metabolism
It is extensively metabolized in the liver, mainly by the cytochrome P450 isoenzymes.
Elimination
Following oral administration, the elimination half-life is 3 to 7 hours.
Drug Management[edit]
Drug Interaction:
Verapamil is metabolized by cytochrome P450 isoenzymes. Clinically significant interactions have been reported with inhibitors of CYP3A4 causing elevation of plasma levels of verapamil hydrochloride while inducers of CYP3A4 have caused a lowering of plasma levels of verapamil hydrochloride, therefore, patients should be monitored for drug interactions.
The following are potential drug interactions associated with verapamil.
Aspirin: concomitant use of verapamil with aspirin may increase the risk of bleeding.
Alpha blockers: verapamil may increase the plasma concentration of prazosin and terazosin which may have an additive hypotensive effect.
Anticonvulsants: verapamil may increase the plasma concentrations of carbamazepine. This may produce side effects such as diplopia, headache, ataxia or dizziness. Verapamil may also increase the plasma concentrations of phenytoin.
Rifampicin: rifampicin may reduce the plasma concentrations of verapamil which may produce a reduced blood pressure lowering effect.
Erythromycin and clarithromycin may increase the plasma concentrations of verapamil.
Beta Blockers: verapamil may increase the plasma concentrations of metoprolol and propranolol which may lead to additive cardiovascular effects (e.g. AV block, bradycardia, hypotension, heart failure)
Digoxin: verapamil has been shown to increase the serum concentration of digoxin and caution should be exercised with regard to digitalis toxicity.
Statins: verapamil may increase the plasma concentrations of atorvastatin and simvastatin.
Anticoagulants, dabigatran etexilate: co-administration of verapamil and dabigatran resulted in increased dabigatran. Closed clinical surveillance is recommended and particularly in the occurrence of bleeding, notably in patients having a mild to moderate renal impairment.
Other: St. John’s Wort may reduce the plasma concentrations of verapamil, whereas grapefruit juice may increase the plasma concentrations of verapamil.
Contraindication:
- Acute porphyrias
- Cardiogenic shock
- Impaired left ventricular function
- Second- or third-degree atrioventricular block
- Severe bradycardia
- Sick sinus syndrome
Pregnancy: avoid
Breast Feeding: amount too small to be harmful.
Hepatic Impairment: reduce dose
Renal Impairment:
FAQ[edit]
How should I take the tablet?[edit]
Swallow the tablet whole with a drink of water. Do not crush the tablet.
What should I avoid while taking?[edit]
Avoid eating grapefruit or drinking grapefruit juice while taking diltiazem. Grapefruit juice can increase diltiazem in your body and make side effects worse, such as flushing or getting headaches.
What happen if I miss a dose?[edit]
If you forget to take a dose and you usually take diltiazem:
- Once a day – take it as soon as you remember, unless it is less than 12 hours until your next dose. In this case, leave out the missed dose and take your next dose at the usual time.
- Twice a day – take it as soon as you remember, unless it is less than 4 hours until your next dose. In this case, leave out the missed dose and take you next dose at the usual time.
- Three times a day – leave out that dose and take your next dose at the usual time.
Do not take a double dose to make up for a forgotten one.
