PHARMACARP EYE DROPS

Indications

• Open-angle glaucoma
• Ocular hypertension

Mechanism of action

Pilocarpine primarily acts as an agonist at muscarinic receptors, particularly M1, M2, and M3 subtypes. Its action at the M3 receptor, a Gq-protein-coupled receptor, leads to the activation of phospholipase C, resulting in increased inositol trisphosphate and intracellular calcium levels. This mechanism enhances smooth muscle contraction, stimulates salivary gland secretion, and induces miosis by contracting the pupillary sphincter and ciliary body muscles. After topical application, the effects on intraocular pressure and miosis occur within 15 to 30 minutes, lasting for 4 to 8 hours.

Pharmacodynamics

Pilocarpine's pharmacodynamic effects include increased secretions from various exocrine glands such as sweat, lacrimal, and salivary glands, resulting in diaphoretic and miotic effects. It significantly increases salivary flow rates, enhancing mucosal moisture, particularly in patients with dry mouth conditions. The drug also increases smooth muscle tone and contractions in the gastrointestinal tract, further contributing to its therapeutic effects. Due to its action on all five muscarinic receptor subtypes, pilocarpine may provoke parasympathetic side effects, including excessive salivation and gastrointestinal upset.

Pharmacokinetics

Pilocarpine is administered topically for ocular conditions and orally for xerostomia. After topical application, it is quickly absorbed, with peak effects on intraocular pressure observed within 2 to 4 hours. The duration of action for miosis is around 4 to 8 hours. Following oral administration, pilocarpine shows a significant increase in salivary secretion, with peak levels maintained for at least one to two hours. The drug is primarily metabolized in the liver, and its metabolites are excreted via urine.

Contra-indications

• Acute iritis
• Uncontrolled asthma

Adverse effects

• Diarrhoea
• Headache
• Hyperhidrosis
• Hypersalivation
• Nausea
• Skin reactions
• Vision disorders
• Vomiting
• Bradycardia
• Bronchospasm
• Conjunctival vascular congestion
• Eye disorder

Interactions

• Beta blockers
• Non-selective beta-adrenergic antagonists

Precautions

• Care in patients with asthma
• Cardiac disease
• Corneal damage
• Epilepsy
• Gastrointestinal conditions
• Parkinson's disease
• Peptic ulceration
• Retinal detachment
• Urinary-tract obstruction

Pregnancy

Avoid unless the potential benefit outweighs risk-limited information available.

Breast-feeding

Avoid unless the potential benefit outweighs risk-no information available.

Storage

Store at room temperature, away from light, and keep out of reach of children.

Formulations

• Pilocarpine 5 mg tablets
• Pilocarpine eye drops

Mechanism of action

The muscarinic M3 receptor is expressed in various endocrine and exocrine glands, including the gastric and salivary glands. It is also found in smooth muscle cells in pupillary sphincter and ciliary bodies. The M3 receptor is a G_q-protein-coupled receptor that activates phospholipase C and upregulates inositol trisphosphate and intracellular calcium. M3 receptor activation has been implicated in smooth muscle contraction and the stimulation of salivary glands. Pilocarpine is an agonist for M1 and M2 receptors, and is a full and partial agonist at the M3 receptor. ...ACT PRIMARILY @ MUSCARINIC RECEPTORS OF AUTONOMIC EFFECTOR CELLS, GANGLIONIC EFFECTS CAN ALSO BE OBSERVED. THIS IS PARTICULARLY TRUE OF PILOCARPINE, ALTHOUGH ITS GANGLIONIC ACTION ALSO INVOLVES STIMULATION OF MUSCARINIC RECEPTORS... ...AFTER TOPICAL INSTILLATION, MIOSIS BEGINS IN 15 TO 30 MIN & LASTS 4 TO 8 HR. REDUCTION OF INTRAOCULAR PRESSURE IS MAXIMAL IN 2 TO 4 HR, WHICH CORRELATES WITH MAX DECR IN OUTFLOW RESISTANCE. EFFECT ON INTRAOCULAR PRESSURE OUTLASTS EFFECT ON OUTFLOW FACILITY...PILOCARPINE...MAY DECR AQUEOUS PRODUCTION. ...PILOCARPINE /HAS AS/...PRINCIPAL ACTION STIMULATION OF SAME AUTONOMIC EFFECTOR CELLS AS THOSE ACTED UPON BY CHOLINERGIC POSTGANGLIONIC NERVE IMPULSES. ...PILOCARPINE...PRINCIPAL ACTION STIMULATION OF SAME AUTONOMIC EFFECTOR CELLS AS THOSE ACTED UPON BY CHOLINERGIC POSTGANGLIONIC NERVE IMPULSES. IN THIS RESPECT...RESEMBLE CHOLINE ESTERS...

Pharmacodynamics

Pilocarpine is a muscarinic agent that mediates diaphoretic, miotic, and central nervous system effects. Pilocarpine stimulates the secretion of various exocrine glands, such as sweat, lacrimal, salivary, and gastrointestinal glands. Following oral administration, pilocarpine increased the mean salivary flow rate by 2- to lO-folds than placebo. Its peak levels were maintained for at least one to two hours. Pilocarpine increases smooth muscle tone, contracts the pupillary and iris sphincter muscles, and induces miosis. Because pilocarpine may affect all five muscarinic receptor subtypes, it is associated with parasympathetic side effects.