A young woman with juvenile myoclonic epilepsy (JME) is treated with valproate but then becomes pregnant. Valproate is considered teratogenic. Its neural tube defect risk is linked to inhibition of which molecular mechanism?

• A Direct inhibition of fetal sodium channels causing neural apoptosis
• B Folate antagonism via dihydrofolate reductase inhibition identical to methotrexate
• C Progesterone receptor blockade causing neural tube dysraphism
• D Inhibition of histone deacetylase (HDAC) altering neural tube gene expression, and folate pathway interference ✓

Explanation

Valproate exerts teratogenic effects primarily through two molecular mechanisms: (1) inhibition of histone deacetylase (HDAC), altering chromatin structure and the epigenetic regulation of neural tube closure genes (including FGF signalling and retinoic acid-responsive genes), and (2) interference with folate metabolism by depleting tetrahydrofolate availability and inhibiting methionine synthase. The combination disrupts neural tube closure during the critical 21–28-day embryonic period, causing spina bifida aperta (risk ~1–2%) and other congenital anomalies. This is why folic acid supplementation (4–5 mg/day preconception and first trimester) is mandatory, though it does not fully eliminate the risk.

Reference: KD Tripathi, Essentials of Medical Pharmacology, 8th ed.

High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP

Written and medically reviewed by the StethoPrep medical team.