Cholinergic and Anticholinergic Drugs: Mechanism, Classification, Dosage, and Effects

Introduction

Cholinergic and anticholinergic drugs play a critical role in pharmacology, affecting the parasympathetic nervous system through various mechanisms. Understanding their dosage, therapeutic uses, and contraindications is essential for safe and effective administration.

Mechanism of Action

Cholinergic Drugs

Cholinergic drugs stimulate the parasympathetic nervous system by mimicking the action of acetylcholine.

• Direct-acting cholinergic agonists (e.g., pilocarpine) bind to cholinergic receptors.
• Indirect-acting cholinergic agonists (e.g., neostigmine) inhibit acetylcholinesterase, increasing acetylcholine levels.

Anticholinergic Drugs

These drugs block acetylcholine action at muscarinic receptors, reducing parasympathetic stimulation.

• Used to treat conditions like bradycardia, asthma, and Parkinson’s disease.
• Common examples include atropine and scopolamine.

Dosage and Administration

Cholinergic Drugs

Dosage varies based on the specific drug and indication:

• Pilocarpine: Typically 5-10 mg per dose for glaucoma.
• Neostigmine: 0.5-2.5 mg IV for myasthenia gravis.

Anticholinergic Drugs

Common dosages include:

• Atropine: 0.5-1 mg IV for bradycardia.
• Ipratropium: 500 mcg via nebulizer for asthma.

Adverse Effects

Cholinergic Drugs

Potential adverse effects include:

• Excessive salivation
• Bradycardia
• Muscle cramps

Anticholinergic Drugs

Possible side effects include:

• Dry mouth
• Blurred vision
• Tachycardia

Therapeutic Indications

Cholinergic drugs are used in conditions such as Alzheimer’s disease and glaucoma, while anticholinergic drugs help in asthma, bradycardia, and overactive bladder.

Contraindications

These drugs should be avoided in patients with conditions like:

• Cholinergic drugs: Asthma, peptic ulcers
• Anticholinergic drugs: Glaucoma, prostate hypertrophy