SMLE Pharmacology 2

Question 1

Which medication is contraindicated in patients with a history of acute intermittent porphyria?

Accepted Answer

Barbiturates

Answer

Barbiturates are strongly contraindicated in acute intermittent porphyria because they induce hepatic cytochrome P450 enzymes, specifically ALA synthase, which increases porphyrin precursor production and can precipitate a life-threatening acute attack.

Question 2

A patient with asthma is prescribed a non-selective beta-blocker for hypertension. What is the expected adverse effect?

Accepted Answer

Bronchospasm

Answer

Non-selective beta-blockers (e.g., propranolol) block beta-2 receptors in bronchial smooth muscle, causing bronchoconstriction. This can precipitate severe bronchospasm in asthmatic patients. Cardioselective beta-blockers (beta-1 selective) are safer but should still be used cautiously.

Question 3

A patient on isoniazid for tuberculosis develops peripheral neuropathy. Which vitamin deficiency is responsible and what supplement prevents this?

Accepted Answer

Vitamin B6 (pyridoxine)

Answer

Isoniazid inhibits pyridoxal phosphokinase and competes with pyridoxal phosphate (active form of vitamin B6), leading to pyridoxine deficiency. This manifests as peripheral neuropathy. Prophylactic pyridoxine (10-25 mg/day) prevents this complication.

Question 4

Which class of antihypertensive drugs is teratogenic and absolutely contraindicated in pregnancy?

Accepted Answer

ACE inhibitors and ARBs

Answer

ACE inhibitors and ARBs are teratogenic, particularly in the second and third trimesters, causing renal agenesis, oligohydramnios, pulmonary hypoplasia, and fetal death. They are absolutely contraindicated throughout pregnancy. Methyldopa and labetalol are safe alternatives.

Question 5

A patient on rifampicin for tuberculosis is also taking warfarin. What effect does rifampicin have on warfarin levels?

Accepted Answer

Decreases warfarin levels (inducer)

Answer

Rifampicin is one of the most potent inducers of cytochrome P450 enzymes (especially CYP3A4, CYP2C9). It accelerates warfarin metabolism, significantly decreasing warfarin levels and anticoagulant effect, requiring substantial dose increases and close INR monitoring.

SMLE Practice Test

SMLE Practice Test

SMLE Pharmacology 2