First Aid USMLE Step 1: Pharmacology Test
Treat toxicity with *aminocaproic acid*, an inhibitor of
fibrinolysis. Fresh frozen plasma and cryoprecipitate can also
be used to correct factor deficiencies.
Aspirin - Correct Answer ✔ ✔ *MOA*:
*IRREVERSIBLY* inhibits cyclooxygenase (both COX-1 and
COX-2) enzyme by covalent acetylation.
Platelets cannot synthesize new enzyme, so effect lasts until
new platelets are produced: ↑ bleeding time, ↓ TXA₂ and ↓
prostaglandins. No effect on PT or PTT.
*Clinical use*:
,Low dose (< 300 mg/day): ↓ platelet aggregation.
Intermediate dose (300-2400 mg/day): antipyretic, analgesic,
anti-inflammatory,
High dose (2400-4000 mg/day): anti-inflammatory.
*Toxicity*:
*Gastric ulceration/upper GI bleed*, tinnitus (CN VIII toxicity).
Chronic use can lead to acute renal failure, interstitial
nephritis, and upper GI bleeding.
Risk of *Reye syndrome* in children treated with aspirin for
viral infection.
,Overdose initially causes hyperventilation and respiratory
alkalosis, but transitions to mixed metabolic acidosis-
respiratory alkalosis.
Clopido*grel*
Ticlopidine
Prasu*grel*
Tica*grel*or - Correct Answer ✔ ✔ *MOA*:
Inhibit platelet aggregation by irreversibly (except ticagrelor)
blocking ADP receptors → prevents expression of GpIIb/IIIa on
platelet surface
*Clinical use*:
, Acute coronary syndrome, coronary stenting, ↓ incidence or
recurrence of thrombotic stroke
Clopidogrel is first line, ticlopidine used when patients cannot
tolerate clopidogrel
*Toxicity*:
*Ticlopidine causes neutropenia* (rare but serious, can
manifest as fever and mouth ulcers. Monitor CBC). TTP may be
seen
Cilostazol
Dipyridamole - Correct Answer ✔ ✔ *MOA*:
Inhibits *platelet phosphodiesterase III* → ↓ breakdown of
cAMP → inhibition of platelet aggregation
Treat toxicity with *aminocaproic acid*, an inhibitor of
fibrinolysis. Fresh frozen plasma and cryoprecipitate can also
be used to correct factor deficiencies.
Aspirin - Correct Answer ✔ ✔ *MOA*:
*IRREVERSIBLY* inhibits cyclooxygenase (both COX-1 and
COX-2) enzyme by covalent acetylation.
Platelets cannot synthesize new enzyme, so effect lasts until
new platelets are produced: ↑ bleeding time, ↓ TXA₂ and ↓
prostaglandins. No effect on PT or PTT.
*Clinical use*:
,Low dose (< 300 mg/day): ↓ platelet aggregation.
Intermediate dose (300-2400 mg/day): antipyretic, analgesic,
anti-inflammatory,
High dose (2400-4000 mg/day): anti-inflammatory.
*Toxicity*:
*Gastric ulceration/upper GI bleed*, tinnitus (CN VIII toxicity).
Chronic use can lead to acute renal failure, interstitial
nephritis, and upper GI bleeding.
Risk of *Reye syndrome* in children treated with aspirin for
viral infection.
,Overdose initially causes hyperventilation and respiratory
alkalosis, but transitions to mixed metabolic acidosis-
respiratory alkalosis.
Clopido*grel*
Ticlopidine
Prasu*grel*
Tica*grel*or - Correct Answer ✔ ✔ *MOA*:
Inhibit platelet aggregation by irreversibly (except ticagrelor)
blocking ADP receptors → prevents expression of GpIIb/IIIa on
platelet surface
*Clinical use*:
, Acute coronary syndrome, coronary stenting, ↓ incidence or
recurrence of thrombotic stroke
Clopidogrel is first line, ticlopidine used when patients cannot
tolerate clopidogrel
*Toxicity*:
*Ticlopidine causes neutropenia* (rare but serious, can
manifest as fever and mouth ulcers. Monitor CBC). TTP may be
seen
Cilostazol
Dipyridamole - Correct Answer ✔ ✔ *MOA*:
Inhibits *platelet phosphodiesterase III* → ↓ breakdown of
cAMP → inhibition of platelet aggregation
