DO Osteopathic Pharmacology 3

Question 1

A patient on digoxin for heart failure develops nausea, yellow-green visual disturbances, and arrhythmias. Which electrolyte abnormality most potentiates digoxin toxicity?

Accepted Answer

Hypokalemia

Answer

Hypokalemia increases digoxin binding to Na+/K+-ATPase since potassium and digoxin compete for the same binding site, greatly potentiating toxicity.

Question 2

A patient is being switched from fluoxetine to phenelzine. Why must a 5-week washout period be observed before starting the MAOI?

Accepted Answer

Fluoxetine and its active metabolite norfluoxetine have exceptionally long half-lives

Answer

Fluoxetine has a half-life of 1-4 days and its active metabolite norfluoxetine has a half-life of up to 1 week, requiring a 5-week washout to prevent serotonin syndrome.

Question 3

A 68-year-old man with both hypertension and benign prostatic hyperplasia (BPH) asks about a single drug that can treat both conditions. Which drug class is appropriate?

Accepted Answer

Alpha-1 adrenergic blockers

Answer

Alpha-1 blockers (e.g., doxazosin, terazosin) relax vascular smooth muscle to lower blood pressure and relax prostatic smooth muscle to improve urinary flow.

Question 4

Which immunosuppressant used in solid organ transplantation works by forming a complex with cyclophilin that inhibits calcineurin?

Accepted Answer

Cyclosporine

Answer

Cyclosporine binds cyclophilin; this complex inhibits calcineurin phosphatase, preventing dephosphorylation of NFAT and blocking IL-2 transcription needed for T-cell activation.

Question 5

A patient with Parkinson's disease is prescribed levodopa/carbidopa. Why is carbidopa included in the formulation?

Accepted Answer

Carbidopa inhibits peripheral DOPA decarboxylase, preserving levodopa for CNS conversion

Answer

Carbidopa inhibits aromatic amino acid decarboxylase (DOPA decarboxylase) in peripheral tissues but does not cross the blood-brain barrier, reducing peripheral dopamine side effects and increasing CNS levodopa availability.

DO - Doctor of Osteopathic Medicine Practice Test

DO - Doctor of Osteopathic Medicine Practice Test

DO Osteopathic Pharmacology 3