Exam 2 Flashcards
Where are muscarinic receptors located?
Heart muscle, sphincters of bladder and gi tract, bronchioles of lungs, sweat glands, iris constrictor
Name the prototype drug that represents the muscarinic agonists. This drug works by reversibly binding directly to and activating muscarinic receptors. It has no effect on nicotinic receptors.
Bethanechol (Urechol)
What 4 areas does bethanechol effect that can cause adverse reactions?
heart, exocrine glands, smooth muscle, and eye
There are three therapeutic uses for bethanechol, one approved one and two invesitgational or off label ones, what are they?
treating urinary retention postoperatively is the approved one, it is also used investigationally for treating GERD and GI paralysis.
Name some of the adverse effects of bethanechol.
cardiovascular effects such as hypotension and bradycardia, alimentary effects such as increased salivation, secretions, diarrhea and involuntary defecation, bronchoconstriction, dysrhythmia in hyperthyroid patients.
Name three sources of toxicology due to muscarinic agonists.
ingestion of inocybe an clitocybe mushrooms, overdose on direct acting musarinic agonists such as bethanechol and pilocarpine, and overdose on cholinesterase inhibitors
What is the treatment for overdose on muscarinic agonists?
atropine - a muscarinic blocking agent
Name the prototype muscarinic antagonist which competitively blocks Acetylcholine action. It can be extracted from plants.
Atropine
Name the seven things that atropine does.
increases heart rate, decreases secretions, relaxes bronchi, decreases bladder tone, decreases GI motility and tone, dilates the pupil and relaxes the ciliary muscle, CNS excitation.
From low to high doses, what areas and in what order does atropine effect?
secretions, heart, eye, urinary tract, intestine, lung, stomach
Name some therapeutic uses for atropine.
preanesthesia to block the baroreceptor reflex and keep heart rate from dropping, eye disorders and exams to cause mydriasis (pupil enlargement) and paralysis of ciliary muscle, bradycardia, intestinal hypertonicity and hypermotility, muscarinic agonist poisoning, peptic ulcer disease, asthma, gall stones (relaxes biliary tract smooth muscle)
Name some adverse effects of atropine.
xerostomia (dry mouth), blurred vision, elevated intraocular pressure, urinary retention, constipation, anhidrosis (low or absent sweat), tachycardia, thickening and drying of bronchial secretions.
What are some sources of antimuscarinic poisoning?
natural products like atropa belladonna and datura stramonium, overdose of atropine or scopolamine, other drugs with pronounced antimuscarinic properties like antihistamines, phenothiazines, antipsychotics, and tricyclic antidepressants.
What are some drugs that atropine interacts with?
any drug that causes muscarinic block - antihistamines, phenothiazine, antipsychotics, tricyclic antidepressants.
What is the treatment for toxicology to muscarinic antagonists?
physostigmine which is a cholinesterase inhibitor, syrup of ipecac and activated charcoal can also be used.
Urinary frequency, urgency, nocturia, and urge incontinence are all symptoms of what pathology?
overactive bladder (OAB)
What class of drugs is used to treat overactive bladder and what is the mechanism of action?
Anticholinergic drugs are used, they work by blocking muscarinic receptors on the bladder detrusor muscle and inhibit bladder contractions and voiding. They block specific M3 receptors (bladder, GI, eye, and salivary glands)
Name some of the anticholinergic drugs used to treat OAB.
oxybutynin (ditropan, oxytrol), darifenacin/enablex (highly M3 selective), solifenacin/vesicare (primarily M3 selective), tolterodone/detrol (nonselective), trospium (sanctura)
Cholinesterase inhibitors are used to treat what condition?
myasthenia gravis
What are the two basic categories of cholinesterase inhibitors?
reversible and irreversible
Name the prototype reversible cholinesterase inhibitor and discuss its mechanism of action.
Neostigmine. It intensifies neurotransmitters action and causes muscarinic responses similar to muscarinic agonists. At the neuromuscular junction it causes increased force of contraction and at toxic levels can cause constant depolarization. Can cause some mild CNS stimulation and CNS depression can result with toxic levels.
Name two therapeutic uses for neostigmine.
myasthenia gravis and reversal of nondepolarizing neuromuscular blockade. (postoperative or OD on muscle relaxant)
What are some adverse reactions of neostigmine?
excessive muscarinic stimulation, neuromuscular blockade - too much Ach at the receptor leads to constant stimulation and paralysis.
Name the only irreversible cholinesterase inhibitor that is used medicinally and what condition is it used to treat?
echothiophate and it is used for glaucoma. It’s pharmacologic effects are exactly like the reversible cholinesterase inhibitors but produces a state of cholinergic crisis.