Carbachol

|} Carbachol (Kar-ba-kol ), also known as carbamylcholine (sold under the brand names Carbastat&reg:, Carboptic&reg:, Isopto Carbachol&reg:, Miostat), is classified as a cholinergic. It is primarily used in the treatment of glaucoma, but is also used during ophthalmic surgery. In most countries it is only available by prescription. Carbachol eyedrops are used to decrease the pressure in the eye for people with glaucoma. It is sometimes used to constrict the pupils during cataract surgery. more...

In the cat and rat, carbachol is well-known for its ability to induce rapid eye movement (REM) sleep when microinjected into the pontine reticular formation. Carbachol elicits this REM sleep-like state via activation of postsynaptic muscarinic cholinergic receptors (mAChRs).

Clinical Info

Chemistry and pharmacokinetics

Carbachol is a choline ester and a positively charged quaternary ammonium compound. It is not well absorbed in the gastro-intestinal tract and does not cross the blood-brain barrier. It is usually administered topical ocular or through intraocular injection. Carbachol is not easily metabolized by cholinesterase, its duration of action is 4 to 8 hours with topical administration and 24 hours for intraocular administration. Since carbachol is poorly absorbed through topical administration, benzalkonium chloride is mixed in to promote absorption.

Mechanisms of action

Carbachol is a parasympathomimetic that stimulates both muscarinic and nicotinic receptors. In topical ocular and intraocular administration its principal effects are miosis and increased aqueous humour outflow.

Indications

Topical occular administration is used to decrease intraocular pressure in people with primary open-angle glaucoma. Intraocular administration is used to produce miosis after lens implantation during cataract surgery. Carbachol can also be used to stimulate bladder emptying if the normal emptying mechanism is not working properly.

Contraindications and precautions

Use of carbachol, as well as all other muscarinic receptor agonists, is contraindicated in patients with asthma, coronary insufficiency, gastroduodenal ulcers, and incontinence. The parasympathomimetic action of this drug will exacerbate the symptoms of these disorders.

Overdose

Sources

• Brenner, G. M. (2000). Pharmacology. Philadelphia, PA: W.B. Saunders Company. ISBN 0-7216-7757-6
• Canadian Pharmacists Association (2000). Compendium of pharmaceuticals and specialties (25th ed.). Toronto, ON: Webcom. ISBN 0-919115-76-4
• Carbachol (1998). MedlinePlus. Retrieved June 27, 2004, from
• Carbachol (2003). RxList. Retrieved June 27, 2004, from
• National Institute for Occupational Safety and Health. (2002). Choline, chloride, carbamate. In The registry of toxic effects of chemical substances. Retrieved June 27, 2004, from
• Carbachol Chloride (2004). Hazardous Substances Data Bank. Retrieved July 16, 2004, from

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