Pharmacology Chapter 12: Cholinergic Drugs

Myasthenia gravis (MG) is a chronic condition with no cure, characterized by antibodies attacking nicotinic synapses on skeletal muscles.
Symptoms of MG include extreme fatigue, diplopia (double vision), speech difficulties, and challenges with chewing or swallowing.
Pyridostigmine (Mestinon) and neostigmine enhance skeletal muscle contraction, alleviating severe muscle weakness.

Cholinergic agonists promote parasympathetic nervous system activity, resulting in increased secretions and muscle contractions.
A cholinergic crisis can occur with symptoms like fever, visual disturbances, and hallucinations, remembered by the phrase "Hot as Hades, blind as a bat, dry as a bone, mad as a hatter."
Bethanechol (Duvoid, Urecholine) stimulates smooth muscle contraction in the digestive and urinary tracts; used for non-obstructive urinary retention in atonic bladder conditions.
Caution is advised during administration; monitor vital signs and be aware of side effects, including increased salivation and hypotension. Atropine serves as a specific antidote.

Anticholinergics inhibit acetylcholine (ACh) at cholinergic synapses, leading to symptoms consistent with "fight-or-flight" response.
Common effects include tachycardia, CNS stimulation, urinary retention, and decreased sweating, potentially causing hyperthermia.
Benztropine (Cogentin) helps alleviate tremors and rigidity in Parkinson's disease.
Scopolamine (Transderm-Scop) is effective for sedation and preventing motion sickness.

Physostigmine serves as an antidote for anticholinergic toxicity by inhibiting ACh breakdown; must be administered slowly to prevent seizures.
Atropine is an anti-bradycardic and antidote for cholinesterase poisoning; it counteracts parasympathetic actions of ACh to stimulate the sympathetic response.
Side effects of atropine include dry mouth, constipation, and potential CNS depression leading to coma. It's contraindicated in patients with glaucoma and certain gastrointestinal obstructions.

Adrenergic receptors are categorized as alpha and beta receptors, each with different physiological roles.
Alpha1 receptors affect all sympathetic target organs except the heart, causing blood vessel constriction and pupil dilation (mydriasis); used in shock treatment and nasal congestion.
Alpha2 receptors inhibit norepinephrine release; they are used to treat hypertension through central nervous system mechanisms.
Beta1 receptors, found in the heart and kidneys, increase heart rate and contractility, alongside renin release; employed in managing cardiac arrest and heart failure.
Beta2 receptors relax smooth muscle and are pivotal in treating asthma and COPD; albuterol is a notable medication used in these cases.