COMLEX/What You Missed From Truelearn

These are mostly concepts/wordings/tip-offs/distinguishing details that I learned from my mistakes on Truelearn and other resources while preparing for COMLEX.

“Prolonged time to release grip” which condition?

Myotonic dystrophy

What is the mechanism of carbamazepine?

prolongs voltage-gated sodium-channel inactivation.

What is the mechanism of carbamazepine?

prolongs voltage-gated sodium-channel inactivation.

Why can warfarin initially cause thrombosis?

Protein C falls rapidly before procoagulant factors → transient hypercoagulable state.

How do you recognize early warfarin hypercoagulability?

New painful skin changes/necrosis shortly after starting warfarin.

How do you recognize flucytosine in a vignette?

Serious systemic fungal infection + antifungal therapy + new cytopenias/bone-marrow suppression.

How do you recognize heparin-induced thrombocytopenia?

Heparin exposure + platelet drop after ~5–10 days + new thrombosis.

What causes heparin-induced thrombocytopenia?

Immunoglobulin G antibodies against the heparin–platelet factor 4 complex → platelet activation and thrombosis.

What is the mechanism of lamotrigine?

Prolongs sodium-channel inactivation → decreases excitatory neurotransmitter release.

How do you recognize maraviroc in a vignette?

HIV drug that prevents viral entry by blocking a host chemokine coreceptor.

What is the mechanism of maraviroc?

Blocks CCR5 on host cells → prevents HIV entry.

Treatment of giant cell arthritis

Glucocorticoids

Lacunar infarcts typically involve the

Basal ganglia

Frontal lobe strokes usual symptoms

Unilateral weakness, hemineglect, aphasia, personality changes

Headaches unsteady gait, in coordination, longstanding uncontrolled hypertension, hemichorea are signs of a

Lacunar infarct

Degradation of the anterior horn causes

Spinal muscular atrophy (SMN1)

“Asymmetrical upper motor neuron symptoms and increased muscle tone”

Cerebral palsy

What’s this a sign of

Megablastic anemia

Which seizure drug inhibits intestinal conjugate to turn folate into an absorbable form

Phenytoin

How do you recognize lamotrigine in a vignette?

Antiseizure or mood-stabilizing drug + painful rash + mucosal involvement → think Stevens-Johnson syndrome/toxic epidermal necrolysis.

What is the mechanism of lamotrigine?

Blocks voltage-gated sodium channels

Pharyngitis + sandpaper rash + strawberry tongue → organism?

Streptococcus pyogenes.

Key morphology/labs of Streptococcus pyogenes?

Gram-positive cocci in chains; beta-hemolytic; bacitracin sensitive; PYR positive.

How do you recognize allopurinol in a vignette?

Chronic gout prevention + severe rash/hypersensitivity. Think xanthine oxidase inhibitor.

What is the mechanism of allopurinol?

Inhibits xanthine oxidase → decreases uric acid production.

How do you recognize irinotecan on boards?

Chemotherapy + prominent diarrhea/abdominal cramping.

What is the mechanism of irinotecan?

Inhibits topoisomerase I.

Inferior atrial septal defect just above the atrioventricular valves = ?

Patent ostium primum.

What is the mechanism of mirtazapine?

Antagonizes presynaptic alpha-2 receptors → increases norepinephrine and serotonin release

How do you recognize mirtazapine in a vignette?

Depression + marked sedation + increased appetite + weight gain.

What junction predominates in the transverse portion of an intercalated disc?

Desmosomes, with fascia adherens, for mechanical attachment. Gap junctions are more lateral and provide electrical coupling.

What is the mechanism of griseofulvin?

disrupts fungal microtubules → inhibits mitosis.

How do you recognize griseofulvin in a vignette?

dermatophyte infection + oral therapy + photosensitivity.

Left-to-right atrial septal defect causes what major ventricular change?

Increased right ventricular volume from right-sided volume overload.

How do you recognize aspirin as an antiplatelet drug?

Acute coronary syndrome/secondary prevention + irreversible platelet inhibition.

How do you recognize valproate in a vignette?

Bipolar disorder or generalized seizures + pregnancy → neural tube defect risk.

What is the mechanism of valproate?

Increases sodium-channel inactivation and increases GABA activity.

How do you recognize an integrase inhibitor question?

HIV therapy + prevents viral genetic material from integrating into the host genome.

What is the mechanism of integrase inhibitors?

Inhibit HIV integrase → prevent insertion of viral DNA into host DNA.

How do you recognize colchicine in a vignette?

Acute gout + severe joint inflammation; think inhibition of neutrophil-mediated inflammation.

What is the mechanism of colchicine?

Disrupts microtubule polymerization → decreases neutrophil chemotaxis and activity

What is the mechanism of bleomycin?

Generates free radicals → DNA strand breaks.

How do you recognize bleomycin in a vignette?

Chemotherapy + progressive dry cough/dyspnea + pulmonary fibrosis.

What ion current causes phase 0 depolarization in sinoatrial and atrioventricular nodal cells?

L-type calcium current.

What is the mechanism of cyproheptadine?

Serotonin receptor antagonist; used for serotonin syndrome.

How do you recognize serotonin syndrome?

Serotonergic drugs + agitation + diaphoresis + hyperreflexia + clonus.

Lateral ventricles + third ventricle enlarged, fourth ventricle normal = blockage where?

Cerebral aqueduct.

How do you recognize warfarin in a vignette?

Oral anticoagulant + monitor PT/INR; bleeding risk; interacts with vitamin K.

What is the mechanism of warfarin?

Inhibits vitamin K epoxide reductase → ↓ activation of factors II, VII, IX, X and proteins C/S.

What is the mechanism of ribavirin?

Interferes with viral RNA synthesis, including inhibition of inosine monophosphate dehydrogenase.

How do you recognize ribavirin in a vignette?

Antiviral therapy + hemolytic anemia. Think chronic hepatitis C treatment in older regimens.

Dilated pupil in oculomotor nerve palsy is due to loss of what fibers?

Preganglionic parasympathetic fibers traveling with cranial nerve III.

Methanol toxicity can damage which basal ganglia structure?

Putamen. Classic clues: homemade alcohol, visual symptoms, severe toxicity

What is the mechanism of methotrexate?

Inhibits dihydrofolate reductase → ↓ tetrahydrofolate → ↓ thymidylate/purine synthesis.

How do you recognize methotrexate in a vignette?

Rheumatoid arthritis/autoimmune disease + oral ulcers + macrocytic anemia ± elevated liver enzymes; leucovorin can rescue toxicity.

Rapid vomiting a few hours after cream-filled pastry/mayonnaise-type food → organism?

Staphylococcus aureus.

Atrophy + fasciculations + decreased reflexes + intact sensation localizes where?

Ventral horn / lower motor neuron.

How do you recognize terbinafine in a vignette?

Onychomycosis/tinea + possible hepatotoxicity → monitor liver enzymes.

What is the mechanism of terbinafine?

Inhibits squalene epoxidase → decreases ergosterol synthesis and causes squalene accumulation

How do you recognize unfractionated heparin on boards?

Immediate anticoagulation + deep venous thrombosis/pulmonary embolism treatment + prolonged partial thromboplastin time.

What is the mechanism of unfractionated heparin?

activates antithrombin III → inhibits thrombin (IIa) and factor Xa.

How do you recognize carbamazepine in a vignette?

Focal seizures or trigeminal neuralgia + diplopia/ataxia + hyponatremia.

What is the mechanism of carbamazepine?

Prolongs the inactivated state of voltage-gated sodium channels → decreases repetitive neuronal firing.

Contralateral loss of pain and temperature from the body localizes to what tract?

Anterolateral system on the opposite side of the spinal cord.

Spasticity + hyperreflexia + loss of vibration/position sense = ?

Subacute combined degeneration from vitamin B12 deficiency → lateral corticospinal tracts + dorsal columns.

What retrograde messenger helps mediate long-term potentiation?

Nitric oxide.

What is the mechanism of cyclophosphamide/ifosfamide?

Alkylate and cross-link DNA.

How do you recognize cyclophosphamide/ifosfamide in a vignette?

Chemotherapy + hemorrhagic cystitis + gross hematuria; think acrolein toxicity.

What is the mechanism of bupropion?

Inhibits norepinephrine and dopamine reuptake.

How do you recognize an echinocandin in a vignette?

Invasive Candida in a very ill or immunocompromised patient; IV antifungal; acts on the fungal cell wall.

What is the mechanism of echinocandins?

inhibit beta-glucan synthesis in the fungal cell wall.

How do you recognize lamotrigine in a vignette?

Antiseizure/mood-stabilizing drug + painful diffuse rash + mucosal involvement → think Stevens-Johnson syndrome.

How do you recognize digoxin toxicity in a vignette?

Heart failure or atrial fibrillation + nausea/vomiting + confusion + yellow-green vision + arrhythmias.

What is the mechanism of digoxin?

Inhibits Na⁺/K⁺-ATPase → increases intracellular Ca²⁺ → increases contractility; also increases vagal tone at the AV node.

How do you recognize milrinone in a vignette?

Severe/decompensated systolic heart failure + short-term IV inotrope + increased contractility + vasodilation.

What is the mechanism of milrinone?

Inhibits phosphodiesterase-3 → increases cyclic AMP → increases cardiac contractility and causes vasodilation.

Common adverse effect of topical retinoic acid?

Erythema and local skin irritation/dryness.

Sore throat + sandpaper rash + strawberry tongue → diagnosis/organism?

Scarlet fever from Streptococcus pyogenes.

Key morphology/labs of Streptococcus pyogenes?

Gram-positive cocci in chains; beta-hemolytic; bacitracin sensitive; PYR positive.

How do you recognize a dihydropyridine calcium-channel blocker?

Hypertension + peripheral/ankle edema + flushing/headache; little direct effect on heart rate compared with verapamil/diltiazem.

Landscaper + nodules spreading along lymphatics = ?

Sporotrichosis from Sporothrix schenckii; dimorphic fungus.

Cervicitis + migratory joint pain/tenosynovitis + pustular rash → organism?

Neisseria gonorrhoeae.

Key morphology/labs of Neisseria gonorrhoeae?

Gram-negative diplococci; oxidase positive; ferments glucose only.

What laboratory finding supports a primary myopathy?

Increased serum creatine kinase from muscle fiber injury.

Key morphology/labs of viridans streptococci?

Gram-positive cocci; alpha-hemolytic; optochin resistant.

Poor dentition or dental procedure + subacute endocarditis → organism?

Viridans streptococci.

How do you recognize amphotericin B in a vignette?

Severe/systemic fungal infection + rising creatinine/nephrotoxicity; often a very sick patient needing broad antifungal therapy.

What is the mechanism of amphotericin B?

Binds ergosterol in fungal cell membranes → forms pores → membrane leakage.

Atrophy + fasciculations + decreased reflexes + intact sensation = lesion where?

Ventral horn/lower motor neuron.

How do you recognize an ARB in a vignette?

Hypertension/diabetic kidney disease + hyperkalemia + no ACE-inhibitor cough.

What is the mechanism of ARBs?

Block angiotensin II AT₁ receptors → decrease vasoconstriction and aldosterone effects.

Parkinson disease — primary site of degeneration?

Substantia nigra pars compacta → loss of dopaminergic neurons → bradykinesia, rigidity, resting tremor.

Which cell produces myelin in the central nervous system?

Oligodendrocyte. Schwann cells produce myelin in the peripheral nervous system.

Slow, effortful speech + preserved comprehension = lesion where?

Dominant inferior frontal gyrus → Broca aphasia.

How is 5-fluorouracil classically recognized on boards?

Board knowledge: chemotherapy + diarrhea/mucositis ± painful red palms/soles (“hand-foot syndrome”).

How do you recognize a TCA in a vignette?

Depression ± neuropathic pain + dry mouth + constipation + blurry vision + urinary retention; overdose can cause arrhythmias.

What is the mechanism of TCAs?

Inhibit serotonin and norepinephrine reuptake.