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Pilocarpine

Pilocarpine, the oldest and most widely used cholinergic agent, derived from the plant pilocarpus microphylus.

Mechanism of action

Angle closure glaucoma
Stimulation of parasympathetic nerve ending → constriction of the pupillary sphincter muscle → miosis → Peripheral iris is pulled away from trabecular meshwork → preventing the crowding of iris at the angle and also it prevents relative pupillary block.
Open angle glaucoma
Pilocar­pine → contraction of longitudinal fibers of the ciliary muscles inserted into the scleral spur → causes opening up of the trabecular pores → increased drainage of aqueous humor.

Pharmacokinetics and Dosage:

Pilocarpine is well absorbed by the cornea and released slowly in to the aqueous. Topically administered, produces a reduction in IOP that starts after one hour and lasts for 4 - 8 hours. The drug is administered every 6 hours to ensure good reduction in IOP. Intraocular penetration of pilocarpine is excellent because of the biphasic solubility of the pilocarpine molecules. Peak IOP lowering effect is seen at 2-3 hours of application and lasts for 6-8 hours.Pilocarpine when given with a polmer vehicle (1.6% polyvinyl pyrolidine) has a prolonged duration of action.

It is available in topical ophthalmic solutions, ocuserts and gel form.

Preparations of Pilocarpine

Topical solution

Pilocarpine hydrochloride in the strengths of 0.25, 0.50, 1, 2, 3, 4, 6, 8, 10%.
Pilocarpine nitrate in the strengths of 1, 2 & 4%.

Gel

Available in 4% and also 1-2% onset of action is 10-30mins and duration is 4-6 hours

Ocusert:

Pilocarpine can be given in ocusert form. Ocusert P - 20, P - 40 or by soft contact lens. Ocuserts are changed weekly and have to be kept in refrigeration at 2°- 8° centigrade.(ocusert 20 mcg is roughly equal to 0.5% to 1% and 40 mcg is about 2 - 4%)

 

Drug interactions

Side effects

Ocular Side effects:

General:

Cornea:

Iris and ciliary body:

Lens:

Posterior segment:

Miscellaneous:

Systemic Side Effects:

Sweating, salivation and lacrimation, nausea, vomiting and abdominal cramps, weakness, fatigue and muscle spasm, paraesthesia, night mare, depression & delusion, prolonged respiratory paralysis after GA, bronchial spasm, asthma and pulmonary edema.

See also: other Cholinergic Agents

Statutory Warning

Materials / Informations provided here are for educational purpose only ; and not to be used for medical advice, diagnosis or treatment