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Carvedilol is an antihypertensive belonging to a class of beta-adrenoreceptor antagonists.

Presentation

Carvedilol is present in forms of 6.25, 12.5, 25 mg tablets.

Clinical Pharmacology of Carvedilol

Carvedilol is a nonselective beta-adrenergic blocking agent with a selective alpha one adrenergic blocking activity.

The principal physiologic action of carvedilol is to completely block adrenergic stimulation of beta receptors within the myocardium (beta 1 receptors) and within bronchial and vascular smooth muscles (beta 2 receptors) and to a lesser extent alpha 1 receptors within the vascular smooth muscle.

The beta1 antagonist activity of carvedilol is similar to that of propanolol and greater than that of labetalol and the duration of carvedilol's effect is longer than those of labetalol and propanolol.

Carvedilol does not exhibit intrinsic sympathomimetic (beta1 agonist) activity and possesses only weak membrane-stabilizing activity.

Pharmacokinetics of carvedilol

Carvedilol is well absorbed from the GI tract but is subjected to fast pass metabolism in the liver; the absolute bioavailability is about 25 %.

Peak plasma concentrations occur in 1-2 hours after an overall dose. It has a high liquid solubility.
Carvedilol is more than 98% bound to plasma proteins.

Its extremely metabolized in the liver, primarily by the P450 isoenzymes CYP2D6 and CYP2C9, and the metabolites are excreted mainly in the bile. The elimination half-life is about 6-10 hours.

Indications of Carvedilol

Carvedilol is used in the management of hypertension and angina pectoris.
It is used as an adjunct to standard therapy in symptomatic heart failure.
It is also used to reduce mortality in patients with left ventricular dysfunction following myocardial infarction.

Dosage

Hypertension:

The initial dose of 12.5mg once daily, increased after 2 days to 25 mg once daily. Alternatively, initial dose of 6.25 mg once daily increased after one to two weeks to 12.5mg twice daily. The dose may be increased further if necessary at intervals of at least two weeks to 50mg once or in divided doses.
A dose of 12.5 mg once daily is enough for the elderly.

Angina Pectoris:

Initial dose, 12.5mg twice daily increased after two days to 25mg twice daily.

Heart Failure:

Initial dose,3.125mg twice daily given with food to reduce the risk of hypotension. If tolerated the dose can be increased to 6.25 mg twice daily and then increased gradually at intervals of not less than two weeks, to maximum dose tolerated.

The dose should not exceed 25mg twice a day in patients with severe heart failure or in those whose weighing less than 85kgs or 50mg twice a day in patients with mild to moderate heart failure weighing more than 85kgs.

Contraindications

Precautions

Carvedilol may cause bradycardia, the dosage should be reduced if the heart rate is less than 55 beats per minute.

May cause hypotension, or syncope.

To decrease the risk of orthostatic hypotension administer with food and strictly adhere to the usual starting dose.

In patients with pheochromocytoma, an alpha one adrenergic blocking should be used before using a beta-adrenergic blocker.

Adverse Effects.

Most of the effects are related to its beta-adrenergic blocking activity. Among them are heart failure, heart block, and bronchospasm.

Cardiovascular: Bradycardia and hypotension, heart failure, or heart block may be precipitated by underlying cardiac disorders.

CNS effects: headache, confusion, hallucinations, sleep disturbances. Fatigue, paraesthesia, peripheral neuropathy, arthralgia, and myopathies.

Nausea and vomiting, diarrhea, constipation, and abdominal cramping are common.


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