Which antihypertensive drug class acts by blocking the conversion of angiotensin I to angiotensin II and is contraindicated in pregnancy due to teratogenicity?

Explanation

## Mechanism of ACE Inhibitors **Key Point:** ACE inhibitors (ACEIs) block angiotensin-converting enzyme, preventing the conversion of angiotensin I (inactive decapeptide) to angiotensin II (potent vasoconstrictor and aldosterone stimulator). ## Teratogenicity in Pregnancy **High-Yield:** ACEIs are contraindicated in all trimesters of pregnancy, particularly the second and third trimesters, causing: - Renal dysgenesis - Oligohydramnios - Intrauterine growth restriction - Fetal hypotension and renal failure - Neonatal death or permanent renal damage **Clinical Pearl:** The critical period is after the first trimester when fetal kidneys begin to develop and become dependent on angiotensin II for glomerular filtration. ## Common ACEIs | Drug | Characteristics | | --- | --- | | Lisinopril | Long-acting, once daily | | Enalapril | Prodrug, requires hepatic conversion | | Ramipril | High tissue penetration | | Captopril | Short-acting, three times daily, causes taste disturbance | **Mnemonic:** **ACEI in pregnancy = AVOID** — Angiotensin-Converting Enzyme Inhibitors are absolutely contraindicated. [cite:KD Tripathi 8e Ch 31]