Cholinergic agonists Flashcards
This drug has almost no nicotinic activity. Duration is up to 2 hours. Poor substrate for acetylcholinesterase. Pharmacological effects: Increased motility and tone in GI tract, stimulates detrusor muscles of bladder, expulsion of urine. Useful in postpartum or postoperative nonobstructive urinary retention.
Bethanechol
This drug is a poor substrate for acetycholinesterase. Duration of action is aprox. 1 hour. Systemic effects: CV and GI stimulation followed by depression, NOT useful therapeutically in systemic administration, Nicotinic action (epi release from adrenal medulla). Pharmacological effects: causes pupillary contraction and decreased intraocular pressure. Used to treat eye glaucoma.
Carbachol
This drug is relatively selective for cardiovascular muscarinic cholinoceptors: Magnitude of response is unpredictable. Therapeutic use limited to vasodilation or cardiac vagomimetic (vagus nerve mimicking): Mimics cardiovascular response to vagus nerve, only use is in diagnosis of asthma (bronchial reactivity testing)
Methacholine
This drug has no medical uses, found in mushrooms. It’s effects cause salivation, mitosis, urination/defecation, sweating, bronchial constriction/secretion, Bradycardia, Nausea/vomiting, headache, hypotension, shock.
Muscarine
This drug is tertiary amine so hydrolyzed by acetycholinesterase. Duration of action up to 2 hours. Muscarinic activity: Less potent than acetylcholine, Uncharged and can penetrate CNS (stimulates profuse sweating and salivation). Therapeutic uses: Used topically in ophthamology, Promotes salivation in patients with xerostomia resulting from irradiation of head and neck.
Pilocarpine
This drug is selective muscarinic (M1 & M3) agonist. Used to treat xerostomia in Sjogrens syndrom. Systemic autoimmune disease where exocrine glands that produce tears and saliva are attacked. Sometimes in combination with pilocarpine.
Cevimeline
This is resistant to Acetylcholinesterase. It also induces paralysis during surgery through depolarizing blockage (brief excitement > widespread fasciculations > flaccid paralysis)
Succinylcholine
This drug has wide effects at muscarinic and nicotinic receptors in ANS and also nicotinic receptors of neuromuscular junction. Duration of action 2-4 hours. Pharmacological effect: increases intestinal and bladder motility, produces miosis and spasm of accomidaiton in eye, lowers intraocular pressure, used to treat overdoses of anticholinergic drugs & TCAs. Adverse effects- rare at therapeutic doses. High doses –> convulsions, bradycardia, decrease cardiac output, accumulation of ACh in NMJ leads to skeletal muscle paralysis
Physostigmine
This drug is polar, does not enter CNS. Greater effect on skeletal muscles than physostigmine. Simulates contractility before paralysis. Duration of action 30 min - 2 hours. Therapeutics effects: stimulates bladder and GI tract, used as antidote for competitive neuromuscular blocking drugs, reduces symptoms of Myasthenia Gravis. Adverse effects: similar to general cholinergic stimulation, no CNS effects.
Neostigmine
drugs to treat Myasthenia Gravis (3)?
Neostigmine, pyridostigmine (3-6 hours), ambenomium (4-8 hours)
Longer duration of action than neostigmine. Only drug approved for medicaid patients in US for MG. Used as antidote to nerve gas in combat.
Pyridostigmine
This drug is structurally related to neostigmine (similar to MOA and adverse reactions). Therapeutic actions: Used in the treatment of chronic glaucoma, diagnosis and treatment of accommodative estropia
Demecarium
This drug is similar to neostigmine but more rapidly to absorbed (short duration of action 10-20 m). Therapeutic effects: used to diagnosis of MG, IV dose leads to rapid increase in muscle strength. Adverse effects: cholinergic crisis with excessive dosing.
Edrophonium
drugs used to treat Alzheimer’s patients.
Tacrine: hepatotoxic
Donepezil: oral bioavailability of 100%, 70 hr 1/2 life
Rivastigmine: transdermal patch, used in dementia/parkinsons patients
Galantimine: natural product, over the counter formulations, sleed aid???
Most commonly used organophosphate insecticide in the US. Rapidly degraded by exposure to sunlight, but trace levels found in water run off, linked to increased ADHD prevalence, used in the treatment of head lice.
Malathion
