PNS Pharmacology Flashcards
4 organs with single (sympathetic) innervation
Blood vessels
Spleen
Piloerector muscles
Sweat glands
Which neurons are cholinergic?
ALL motor neurons to skeletal muscle
ALL preganglionic autonomic neurons
ALL postganglionic parasympathetic neurons
Some postganglionic sympathetic neurons (sweat glands, some blood vessels in skeletal muscle)
Carbachol Class Use Mechanism Administration Adverse rxns
Muscarinic agonist
Constricts iris and ciliary body → miosis during surgery and reduced IOP following cataract surgery
•Agonist at muscarinic receptors, but also has strong nicotinic (Nn) activity
•Administered directly to eye
•Not inactivated by AchE → long duration
•Adverse rxns: rare iritis or corneal clouding
Methacholine Class Use Mechanism Reversal Precaution
Muscarinic agonist
Used for diagnosis of airway hyperreactivity. Inhaled.
•Agonist at muscarinic receptors. Less nicotinic activity than carbachol.
•If bronchoconstriction occurs, administer albuterol (B2 agonist → bronchodilation)
•Precaution: asthma
Bethanechol Class Use Mechanism Precautions
Muscarinic agonist
Promotes GI and urine motility following surgery or due to postpartum nonobstructive urinary retention.
•Muscarinic agonist w/ zero nicotinic activity
•Precautions – urinary tract obstruction
Pilocarpine Class Use Mechanism Adverse rxns Precautions
Muscarinic agonist
Treats glaucoma by contracting ciliary and circular muscles (M3) → miosis and increased outflow of aqueous humor. Also treats xerostomia caused by Sjogren’s Syndrome and salivary gland dysfunction.
•Muscarinic agonist
•Adverse rxns: blurred vision, hypersalivation, diaphoresis, flushing
•Precautions: asthma, iritis, posterior synechiae (adhesion b/w iris and lens), retinal detachment
Nicotine Class Use Mechanism Adverse rxns Precautions
Nicotinic agonist
•Smoking cessation
•Agonist at Nm and Nn receptors
•Stimulates catecholamine release.
•Adverse rxns: CNS (dizziness, insomnia, irritability), CV (increased BP due to increased inotropic / chronotropic actions)
•Precautions: CV problems, pregnancy category D
Varenicline Use Mechanism Adverse rxns Precautions
Smoking cessation
•Partial agonist at alpha4-beta2 nicotinic receptors in brain. Moderate serotinin activity.
•Adverse rxns: GI (nausea, constipation, farts), CNS (insomnia, vivid dreams, irritability, hostility)
•Precautions – renal insufficiency and black box warning for changes in behavior, such as hostility, agitation, depression, and suicide
Physostigmine Class Use Mechanism Adverse rxns Precautions
Acetylcholinesterase antagonist
DOC to counteract toxic anticholinergic effects of other drugs. Also treats glaucoma.
•Carbamoyl ester class – Competes w/ Ach at binding site of AchE. Carbamoylates AchE to inactivate it. Mimics increased Ach.
•Adverse rxns: SLUDGE
• CNS: restlessness, seizures
• CV: irregular pulse, palpitations, bradycardia
• GI: hypersalivation, cramps, NVD
• UG: urinary urgency
• Lung: bronchospasm, dyspnea, ↑ secretions
• Eye: miosis, lacrimation, blurred vision
•Precautions: asthma, GI obstruction (obstructive ileus), urinary tract obstruction
Neostigmine Class Use Mechanism Adverse rxns Precautions
AchE inhibitor
Treats myasthenia gravis (autoantibodies target NMJ Ach receptors), neurogenic ileus, and postop reversal of NMJ blocker
•Carbamoyl ester class – same mechanism as physostigmine.
•Good to use for neurogenic ileus b/c it’s charged, so it only affects PNS, not CNS
•Adverse rxns:
• CV: irregular pulse, palpitations, bradycardia
• GI: hypersalivation, cramps, NVD
• UG: urinary urgency
• Lung: bronchospasm, dyspnea, ↑ secretions
• Eye: miosis, lacrimation, blurred vision
•Precautions: asthma, obstructive ileus, urinary tract obstruction, peptic ulcer
• Ach stimulates acid secretion → ulcers
Edrophonium Class Use Mechanism Adverse rxns
AchE inhibitor
DOC for diagnosing myasthenia gravis. Also treates ileus and reverses NMJ blockers after surgery.
•Alcohol – competitive inhibitor for Ach at AchE
• Very rapid action and short duration. Not good for tx of myasthenia gravis.
•Adverse rxns:
• Dysphonia, dysarthia, dysphagia, convulsions
• CV: irregular pulse, palpitations, bradycardia
• GI: hypersalivation, cramps, NVD
• UG: urinary urgency
• Lung: bronchospasm, dyspnea, ↑ secretions
• Eye: miosis, lacrimation, blurred vision
•Precautions: obstructive ileus, urinary tract obstruction
Echothiophate Class Use Mechanism Adverse rxns
AchE inhibitor
2nd line tx for open angle glaucoma
•Organophosphate class. Phosphorylates / inhibits AchE.
•Adverse rxns: eye stinging, blurred vision, cataracts
Pralidoxime Class Use Mechanism Time frame Adverse rxns Precautions
Opposite of other drugs. Reverses organophosphate AchE inhibition (restores function). Also reverses effects of neostigmine (myasthenia gravis tx)
•Displaces phosphoryl group via hydroxylation. Must be given w/in 24 hours of organophosphate exposure.
•Adverse rxns:
• CV: tachycardia, hypertension
• Elevated LFTs
• Eye: diplopia, blurred vision
•Precautions: renal insufficiency, myasthenia gravis
Atropine Class Use Mechanism Adverse rxns Precautions
Muscarinic antagonist
Treats bradycardia, reduces secretions for preop, promotes mydriasis and cycloplegia (lack of accommodation) for ophthalmic exams, decreases detrusor tone, decreases GI motility, and bronchodilation. Also used as antidote for AchE inhibitor or muscarinic agonist poisoning.
•Competitive antagonist at muscarinic receptors. Doesn’t effect AchE enzyme (this is main diff from pralidoxime for poison antidote).
•Blocks M2 receptors on heart → increased HR
•Don’t use atropine to produce bronchodilation for asthma b/c it affects so many other things before that occurs.
•Adverse rxns: CNS (confusion, amnesia, hallucinations, delerium, insomnia) and CV (conduction abnormalities, fibrillation, QT prolongation).
•Precautions – acute MI, bladder obstruction, urinarty tract obstruction, prostatic hypertrophy, glaucoma, obstructive ileus, hyperthyroidism.
Oxybutynin Class Use Mechanism Adverse rxns Precautions
Muscarinic antagonist
Bladder muscle relaxant. Used for neurogenic bladder to treat urge incontinence.
•Competitive muscarinic receptor antagonist. Anti-muscarinic effect not as strong as atropine, but antispasmotic activity on detrusor muscle is 4-10x stronger.
•Adverse rxns: heart palpitations, tachycardia, constipation / diarrhea
•Precautions:
• GI obstruction, ileus
• Toxic megacolon, ulcerative colitis
• Urinary retention or urinary tract obstruction
• Uncontrolled narrow-angle glaucoma
Ipratropium Class Use Mechanism Adverse rxns Precautions
Muscarinic antagonist
Tx acute asthma attacks. First line therapy for COPD. Combine w/ B2 agonists.
•Muscarinic receptor antagonist blocks Ach from causing bronchoconstriction (M3).
•Adverse rxns: xerostomia, cough, throat irritation
•Precautions: glaucoma, urinary retention, bladder obstruction
Mecamylamine Class Use Mechanism Adverse rxns
Ganglionic antagonist
Mainly treats HTN. Some use for Tourette’s Syndrome and nicotine withdrawal.
•Competitive antagonist at Nn receptors.
•Adverse rxns: orthostatic hypotension b/c baroreceptor reflex doesn’t work. Can’t vasoconstrict.
Epinephrine Class Use Mechanism Metabolism Precautions
Adrenergic agonist
Tx for bronchospasm, asthma, CPR. DOC for anaphylaxis. One of most potent vasopressors known. Often combined w/ local anesthetics to prolong duration. Decreases IOP for open-angle glaucoma and produces brief mydriasis.
•Activates both alpha and beta receptors
•Metabolized by COMT and MAO in liver
•Precautions: narrow-angle glaucoma, extravasion (skin necrosis), labor
Ephedrine
Class
Use
Mechanism
Adrenergic agonist
Tx asthma. Also works as a psychostimulant.
•Agonist at alpha and beta receptors. Also blocks NE reuptake. Both direct and indirect acting.
Phenylephrine Class Use Mechanism Precautions
Adrenergic agonist
Tx nasal congestion. Induces mydriasis for ophthalmic exam.
•Selective A1 agonist → vasoconstriction
•Adverse rxns: CV, HTN, narrow angle glaucoma, labor