Muscarinic Blockers and Their Effects

This page focuses on muscarinic blockers, a type of cholinergic antagonist. Atropine is the prototype muscarinic blocker, with various derivatives used for different purposes. For instance, hyoscine (scopolamine) is used to prevent motion sickness, often administered as a transdermal patch.

The page describes the classic anticholinergic effects using the mnemonic "dry as a bone, blind as a bat, hot as a hare, red as a beet." These effects include dry mouth, blurred vision, hyperthermia, and flushed skin.

Various muscarinic blockers are listed with their specific uses, such as ipratropium and tiotropium for asthma and COPD, and drugs like oxybutynin and tolterodine for overactive bladder.

Vocabulary: Anticholinergic effects - The physiological effects resulting from the blocking of acetylcholine receptors.

Example: Ipratropium, a quaternary derivative of atropine, is used as a bronchodilator in asthma treatment due to its more peripheral effects on the lungs and reduced CNS effects.

Ganglionic and Neuromuscular Blockers

This final page discusses ganglionic blockers and neuromuscular blockers, both types of cholinergic antagonists. Ganglionic blockers, such as hexamethonium, block neurotransmission at nicotinic receptors in autonomic ganglia.

Neuromuscular blockers are divided into two categories:

1. Non-depolarizing, competitive, reversible blockers (e.g., tubocurarine, atracurium) used as muscle relaxants.
2. Depolarizing, irreversible, non-competitive blockers, with succinylcholine being the only one in clinical use.

The page highlights the risk of malignant hyperthermia associated with succinylcholine use, a life-threatening condition caused by excessive calcium release due to overactivation of ryanodine receptors.

Highlight: Succinylcholine, the only depolarizing muscle relaxant in clinical use, can cause malignant hyperthermia, a potentially fatal complication.

Vocabulary: Malignant hyperthermia - A severe reaction to certain anesthetic drugs, characterized by rapid temperature increase, muscle rigidity, and metabolic acidosis.