Autonomic lecture: Parasympathomimetics Flashcards
analogs
bethanechol
plant parasympathomimetics
cevimeline
muscarine
pilocarpine
what are the problems with Acetylcholine as a drug
- ineffective orally-> quaternary structure, not lipid soluble, can’t absorb it
- injection: very brief action and not specific, rxn all over body - effects fleeting: seconds or minutes due rapid hydrolysis
- widespread effects on injection of ACh
- analogs are made
bethanechol (Urecholine)
beta, methyl carbachol
- absorbed p.o. despite quaternary structure
- used in post-partem or post-operative urinary retention, atony in GI tract, after child birth(stimulates bladder)
- not gonna be broken down
- stimulates muscarinic receptors throughout body
cevimeline (Evoxac) is used to
correct dryness of mouth and URT
-after head and neck irradiation and in Sjogren’s syndrome to correct dryness
muscarine
alkaloid from mushroom (amanita muscaria)
-not used as a drug
pilocarpine (Isopto Carpine)
- miotic in glaucoma
- constrict pupil of eye to bring pressure down
- partial agonist: less headache, less irritation, cheaper
- relieves block of canal of Schlemm
what is pilocarpine used for?
glaucoma
-intraocular pressure increases to 30-40 mmHg
what does pilocarpine block?
canal of Schlemm blocked
- opens up canal and fluid flows out
- flow of aqueous humor is flow, 3mm a day
what are the types of glaucoma
narrow angle
wide angle: 65% of patients, have to use drugs the rest of their life
drugs used to treat glaucoma
beta blockers
prostaglandins
-dont act fast, take hours
pilocarpine for narrow angle emergencies
precautions to muscarine drugs
asthma: don’t want stimulate those receptors
hyperthyroidism
instead of an acetic acid ester in ACh, what is it replaced with?
carbamic acid ester
-resistant to degradation, long action
muscarine receptors
M1-> brain, PIP2
M2-> heart-> decrease cAMP
M3-> smooth muscle-> PIP2
