Cholinergic Drugs

For a review of the effects of cholinergic receptors and metabolism, see here: Cholinergics

Muscarinic Agonists (Parasympathetic)

Stimulates the parasympathetic nervous system. The following either have an extra methyl group, a terminal NH2 group, or both which makes it harder to break down by AchE.

Bethanechol

Taken orally after surgery to restart GI activity. Will also open urinary smooth muscle.

Pilocarpine

Stimulates sweat, tears, and saliva which is good for closed-angle glaucoma and xerostomia (Sjogren syndrome). Also used as eye drops for Presbyopia (age related vision deficits).

Methacholine

Stimulates airway, causing wheezing. Challenge test for asthma.

Carbachol

Constricts the pupil and relieves intraocular pressure, which is good for open-angle glaucoma.

Cholinesterase Inhibitors (Parasympathetic)

Acetylcholinesterase (AchE) is found in the synaptic cleft, red blood cells, placenta, and tendons. Plasma cholinesterase is non-specific and will metabolize any ester.

Carbamic acid derivatives

Steric hinderance from nitrogen makes it hard to release the final products, slowing down the esterase reaction and increasing concentration of Ach.

Physostigmine

Original carbamic acid derivative. Can be taken orally.

Neostigmine

Used in operating rooms to reverse curare.

Pyridostigmine

Used to treat myasthenia gravis by blocking breakdown of Ach.

Rivastigmie & Donepezil

Medications used to treat Alzheimer's disease which is caused by degeneration of cholinergic nerves. This will prolong cognitive function.

Edrophonium

Used in operating rooms to reverse curare.

Clinical Pearl: Reversing Curare

Giving AchE inhibitors to increase the amount of Ach will reverse the effects of curare at the NMJ. To insure the Ach doesn't also affect muscarinic targets, an anticholinergic like atropine can be administered to inhibit those receptors.

Organophosphates (Parasympathetic)

These are also cholinesterase inhibitors, but will permanently (irreversibly) shut off AchE.

Echothiopate

The only AchE with a phosphate group used in medicine. Given as eye drops for treatment of glaucoma.

Chemical warfare agents

WWII era weapons. Thoughtful gifts for kids younger than 7. Can be treated with pralidoxime.

Muscarinic Antagonists (Sympathetic)

Also known as antimuscarinics or anticholinergics. Stimulates the sympathetic nervous system via blocking the parasympathetic.

Atropine

Can cross the blood brane barrier can cause mental fog and confusion. Used in surgery to reduce saliva and can be used as treatment for mushroom poisoning. Can also be used in emergencies to treat bradycardia.

Scopolamine

Used for motion sickness.

Homatropine

Used as eye drops for pupil dilation.

Ipratropium/tiotropium

Administered through insufflation via an inhaler to dilatate bronchioles/reduce secretions.

Tolterodine

Treats overactive bladder. Has dry mouth, constipation, headache, and stomach pain as side effects.

Glycopyrronium

Treats hyperhidrosis (excessive sweating). Has dry mouth, blurred vision, and urinary retention as side effects.

Nicotinic Antagonists (Sympathetic)

Either block nicotinic muscle receptors or nicotinic neuronal receptors. Drugs which have charge centers 10C apart will block muscle receptors while charge centers 6C apart will block neuronal receptors.

Curare

Competitive antagonist of Ach. Decreases size of excitatory potential and does not generate action potential, resulting in muscle paralysis.

Hexamethonium

Discontinued ganglionic blocking drug.

Trimethaphan & Mecamylamine

Ganglionic blocking drugs. Diffuse mechanism which used to be used for severe hypertension.