A 28-year-old woman with idiopathic pulmonary arterial hypertension is started on an oral agent that improves exercise capacity and delays clinical worsening. Before prescribing, the clinician must exclude pregnancy and check baseline liver function because the drug:

• A Is a prostacyclin analog causing severe hypotension
• B Is a soluble guanylate cyclase stimulator associated with hypothyroidism
• C Is a phosphodiesterase 5 inhibitor that causes retinal ischemia
• D Is an endothelin receptor antagonist that is embryotoxic and hepatotoxic ✓

Explanation

Bosentan is a dual ETA and ETB endothelin receptor antagonist used in PAH. Endothelin signaling is essential for fetal development, so bosentan is strongly teratogenic and absolutely contraindicated in pregnancy, mandating reliable contraception. It also causes dose-dependent transaminase elevation requiring monthly liver function monitoring. Ambrisentan, a selective ETA blocker, shares these concerns. The other options describe riociguat, prostacyclins, and sildenafil respectively.

Reference: Katzung's Basic and Clinical Pharmacology, 15th ed.

High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP

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