Cholinergic antagonists

Question 1

Belladonna alkoid. High affinity competitive antagonism at muscarinic receptors. Duration of action is ~ 4 hours (ocular administration can last for days). “core” therapeutic agent in WHO’s essential drug list (antidote for cholinergic agonists especially organophosphate poisoning)

Answer 1

Atropine

Question 2

Long acting (not used for acute). Useful in asthma patients who are contraindicated for adrenergic agonists. Useful for COPD (inhaled formulations, positively charged so does not enter systemic circulation or CNS). Somewhat more efective than ipratropium.

Answer 2

Tiotropium

Question 3

Belladona alkaloid. Simliar effects to atropine. Longer duration of action, more significant CNS effects. Pharmacological effects: Low dose (most effective anti-motion sickness drug, blocks short term memory, sedation). High dose (may produce euphoria/excitement)

Answer 3

Scopolamine

Question 4

Competitive nicotinic blockade of ganglia. Duration of action ~ 10 hours. Primarily used to lower blood pressure in emergency situations (antihypertensive, widens blood vessels and increases blood flow). Pharmacological research suggests at low does could be effects as anti-smoking drug.

Answer 4

Mecamylamine

Question 5

One of the most toxic substances known to man. Degrades SNAP-25 (prevents synaptic vesicle fusion in presynaptic membrane, no acetylcholine is released into synaptic cleft). Therapeutic uses: cosmetic, disease associated with increased muscle tone. Adverse effects: Antibodies develop, repeated dosing required, generally well tolerated, but can be severe.

Answer 5

Botulinum toxin