USMLE STEP 1 Pharmacology
LAEST EXAM QUESTIONS AND
REVISED SOLUTIONS
Tetrodotoxin - ANSWER ✔ -Poisoning can result from ingestion of
poorly prepared puffer fish (exotic sushi)
-Highly potent toxin that binds fast voltage-gated Na+ channels in
cardiac and nerve tissue, preventing depolarization - blocks action
potential without changing resting potential (same mechanism as
Lidocaine)
-Causes nausea, diarrhea, paresthesias, weakness, dizziness,
loss of reflexes.
-Treatment is primarily supportive.
Ciguatoxin - ANSWER ✔ -Consumption of reef fish (e.g.
barracuda, snapper, eel...)
-Causes ciguatera fish poisoning.
-Opens Na+ channels causing depolarization. Symptoms easily
confused with cholinergic poisoning.
-Temperature-related dysesthesia (e.g., "cold feels hot; hot feels
cold") is regarded as a specific finding of ciguatera.
-Treatment is primarily supportive.
Scombroid poisoning - ANSWER ✔ -Caused by consumption of
dark-meat fish (e.g., bonito, mackerel, mahi-mahi, tuna)
improperly stored at warm temperature.
-Bacterial histidine decarboxylase converts histidine to histamine.
Histamine is not degraded by cooking.
,-Acute-onset burning sensation of the mouth, flushing of face,
erythema, urticaria, pruritus, headache. May cause anaphylaxis-
like presentation (i.e., bronchospasm, angioedema, hypotension).
-Frequently misdiagnosed as allergy to fish.
-Treat supportively with antihistamines; if needed,
antianaphylactics (e.g., bronchodilators, epinephrine).
Albuterol - ANSWER ✔ -β2 > β1 direct agonist
-Acute asthma
Salmterol - ANSWER ✔ -β2 > β1 direct agonist
-Long term asthma or COPD control
Dobutamine - ANSWER ✔ -β1 > β2, α direct agonist
-Uses: heart failure (HF) (inotropic > chronotropic), cardiac stress
testing.
Dopamine - ANSWER ✔ -D1 = D2 > β > α direct agonist
-Uses: unstable bradycardia, HF, shock; inotropic and
chronotropic α effects predominate at high doses.
Epinephrine - ANSWER ✔ -β > α direct agonist
-Uses: anaphylaxis, asthma, open-angle glaucoma;
α effects predominate at high doses. Significantly stronger effect
at β2-receptor than norepinephrine.
Isoprterenol - ANSWER ✔ -β1 = β2 direct agonist
-Uses: electrophysiologic evaluation of tachyarrhythmias. Can
worsen ischemia
Norepinephrine - ANSWER ✔ -α1 > α2 > β1 direct agonist
-Hypotension (butrenal perfusion). Significantly weaker effect at
β2-receptor than epinephrine.
, Phenylephrine - ANSWER ✔ -α1 > α2 direct agonist
-Uses: hypotension (vasoconstrictor), ocular procedures
(mydriatic), rhinitis (decongestant)
Amphetamine - ANSWER ✔ -Indirect general sympathetic
agonist
-reuptake inhibitor; also releases stored catecholamines
-Narcolepsy, obesity, ADHD.
Cocaine - ANSWER ✔ -Indirect general sympathetic agonist
-Reuptake inhibitor
-Causes vasoconstriction and local anesthesia.
-Never give β-blockers if cocaine intoxication is
suspected (can lead to unopposed α1 activation and extreme
hypertension).
Ephedrine - ANSWER ✔ -Indirect general sympathetic agonist
-Releases stored catecholamines
-Nasal decongestion, urinary incontinence, hypotension.
Norepinephrine vs. isoproterenol - ANSWER ✔ -Norepinephrine
increases systolic and diastolic pressures as a result of α1-
mediated vasoconstriction causing increased in mean arterial
pressure and reflex bradycardia. -However, isoproterenol (no
longer commonly used) has little α effect but causes β2-mediated
vasodilation, resulting in decreased mean arterial pressure and
increased heart rate through β1 and reflex activity.
Clonidine - ANSWER ✔ -α2-agonist
-Uses: hypertensive urgency (limited situations); does not
decrease renal blood flow; ADHD, Tourette syndrome
-Toxicity: CNS depression, bradycardia, hypotension, respiratory
depression, miosis
, α-methyldopa - ANSWER ✔ -α2-agonist
-Used for hypertension in pregnancy
-Toxicity: Direct Coombs ⊕ hemolysis, SLE-like syndrome
Phenoxybenzamine - ANSWER ✔ -Nonselective α-blocker
-Irreversible
-Used preoperatively for pheochromocytoma to prevent
catecholamine (hypertensive) crisis
-Toxicity: orthostatic hypotension, reflex tachycardia
Phentolamine - ANSWER ✔ -Nonselective α-blocker
-Give to patients on MAO inhibitors who eat tyramine containing
foods
-Toxicity: orthostatic hypotension, reflex tachycardia
Prazosin - ANSWER ✔ -Selective α1-blocker
-Uses: urinary symptoms of BPH; PSTD
-Hypertension
-Toxicity: 1st-dose orthostatic hypotension, dizziness, headache
Terazosin - ANSWER ✔ -Selective α1-blocker
-Uses: urinary symptoms of BPH;
-Hypertension
-Toxicity: 1st-dose orthostatic hypotension, dizziness, headache
Doxazosin - ANSWER ✔ -Selective α1-blocker
-Uses: urinary symptoms of BPH;
-Hypertension
-Toxicity: 1st-dose orthostatic hypotension, dizziness, headache
Tamsulosin - ANSWER ✔ -Selective α1-blocker
-Uses: urinary symptoms of BPH;
-Toxicity: 1st-dose orthostatic hypotension, dizziness, headache
LAEST EXAM QUESTIONS AND
REVISED SOLUTIONS
Tetrodotoxin - ANSWER ✔ -Poisoning can result from ingestion of
poorly prepared puffer fish (exotic sushi)
-Highly potent toxin that binds fast voltage-gated Na+ channels in
cardiac and nerve tissue, preventing depolarization - blocks action
potential without changing resting potential (same mechanism as
Lidocaine)
-Causes nausea, diarrhea, paresthesias, weakness, dizziness,
loss of reflexes.
-Treatment is primarily supportive.
Ciguatoxin - ANSWER ✔ -Consumption of reef fish (e.g.
barracuda, snapper, eel...)
-Causes ciguatera fish poisoning.
-Opens Na+ channels causing depolarization. Symptoms easily
confused with cholinergic poisoning.
-Temperature-related dysesthesia (e.g., "cold feels hot; hot feels
cold") is regarded as a specific finding of ciguatera.
-Treatment is primarily supportive.
Scombroid poisoning - ANSWER ✔ -Caused by consumption of
dark-meat fish (e.g., bonito, mackerel, mahi-mahi, tuna)
improperly stored at warm temperature.
-Bacterial histidine decarboxylase converts histidine to histamine.
Histamine is not degraded by cooking.
,-Acute-onset burning sensation of the mouth, flushing of face,
erythema, urticaria, pruritus, headache. May cause anaphylaxis-
like presentation (i.e., bronchospasm, angioedema, hypotension).
-Frequently misdiagnosed as allergy to fish.
-Treat supportively with antihistamines; if needed,
antianaphylactics (e.g., bronchodilators, epinephrine).
Albuterol - ANSWER ✔ -β2 > β1 direct agonist
-Acute asthma
Salmterol - ANSWER ✔ -β2 > β1 direct agonist
-Long term asthma or COPD control
Dobutamine - ANSWER ✔ -β1 > β2, α direct agonist
-Uses: heart failure (HF) (inotropic > chronotropic), cardiac stress
testing.
Dopamine - ANSWER ✔ -D1 = D2 > β > α direct agonist
-Uses: unstable bradycardia, HF, shock; inotropic and
chronotropic α effects predominate at high doses.
Epinephrine - ANSWER ✔ -β > α direct agonist
-Uses: anaphylaxis, asthma, open-angle glaucoma;
α effects predominate at high doses. Significantly stronger effect
at β2-receptor than norepinephrine.
Isoprterenol - ANSWER ✔ -β1 = β2 direct agonist
-Uses: electrophysiologic evaluation of tachyarrhythmias. Can
worsen ischemia
Norepinephrine - ANSWER ✔ -α1 > α2 > β1 direct agonist
-Hypotension (butrenal perfusion). Significantly weaker effect at
β2-receptor than epinephrine.
, Phenylephrine - ANSWER ✔ -α1 > α2 direct agonist
-Uses: hypotension (vasoconstrictor), ocular procedures
(mydriatic), rhinitis (decongestant)
Amphetamine - ANSWER ✔ -Indirect general sympathetic
agonist
-reuptake inhibitor; also releases stored catecholamines
-Narcolepsy, obesity, ADHD.
Cocaine - ANSWER ✔ -Indirect general sympathetic agonist
-Reuptake inhibitor
-Causes vasoconstriction and local anesthesia.
-Never give β-blockers if cocaine intoxication is
suspected (can lead to unopposed α1 activation and extreme
hypertension).
Ephedrine - ANSWER ✔ -Indirect general sympathetic agonist
-Releases stored catecholamines
-Nasal decongestion, urinary incontinence, hypotension.
Norepinephrine vs. isoproterenol - ANSWER ✔ -Norepinephrine
increases systolic and diastolic pressures as a result of α1-
mediated vasoconstriction causing increased in mean arterial
pressure and reflex bradycardia. -However, isoproterenol (no
longer commonly used) has little α effect but causes β2-mediated
vasodilation, resulting in decreased mean arterial pressure and
increased heart rate through β1 and reflex activity.
Clonidine - ANSWER ✔ -α2-agonist
-Uses: hypertensive urgency (limited situations); does not
decrease renal blood flow; ADHD, Tourette syndrome
-Toxicity: CNS depression, bradycardia, hypotension, respiratory
depression, miosis
, α-methyldopa - ANSWER ✔ -α2-agonist
-Used for hypertension in pregnancy
-Toxicity: Direct Coombs ⊕ hemolysis, SLE-like syndrome
Phenoxybenzamine - ANSWER ✔ -Nonselective α-blocker
-Irreversible
-Used preoperatively for pheochromocytoma to prevent
catecholamine (hypertensive) crisis
-Toxicity: orthostatic hypotension, reflex tachycardia
Phentolamine - ANSWER ✔ -Nonselective α-blocker
-Give to patients on MAO inhibitors who eat tyramine containing
foods
-Toxicity: orthostatic hypotension, reflex tachycardia
Prazosin - ANSWER ✔ -Selective α1-blocker
-Uses: urinary symptoms of BPH; PSTD
-Hypertension
-Toxicity: 1st-dose orthostatic hypotension, dizziness, headache
Terazosin - ANSWER ✔ -Selective α1-blocker
-Uses: urinary symptoms of BPH;
-Hypertension
-Toxicity: 1st-dose orthostatic hypotension, dizziness, headache
Doxazosin - ANSWER ✔ -Selective α1-blocker
-Uses: urinary symptoms of BPH;
-Hypertension
-Toxicity: 1st-dose orthostatic hypotension, dizziness, headache
Tamsulosin - ANSWER ✔ -Selective α1-blocker
-Uses: urinary symptoms of BPH;
-Toxicity: 1st-dose orthostatic hypotension, dizziness, headache
