Carbachol is a synthetic choline ester that acts as a potent cholinergic agonist. It is commonly used in ophthalmology for the treatment of glaucoma and in the diagnosis of certain eye conditions. Carbachol acts on both muscarinic and nicotinic receptors, stimulating the parasympathetic nervous system.
In the eye, carbachol stimulates the muscarinic receptors in the iris sphincter muscle and ciliary muscle, causing miosis (pupillary constriction) and accommodation (focusing of the lens). This helps to lower intraocular pressure in glaucoma by increasing the outflow of aqueous humor.
Carbachol is also used in the diagnosis of Horner’s syndrome, which is a condition characterized by ptosis (drooping of the eyelid), miosis (pupillary constriction), and anhidrosis (absence of sweating) on one side of the face. When carbachol is administered to the affected eye, it causes a greater pupillary constriction compared to the unaffected eye, indicating that there is a problem with the sympathetic nervous system on that side of the face.
While carbachol is generally well-tolerated, it can cause side effects such as headache, nausea, and gastrointestinal upset. In some cases, it can also cause systemic effects such as bradycardia (slow heart rate) and hypotension (low blood pressure). It is important to use carbachol only as directed by a healthcare professional.
