Correct Answer: A. 14 grams
The Pritchard regimen is the gold-standard magnesium sulfate protocol for seizure prophylaxis in preeclampsia/eclampsia, widely adopted in Indian obstetric practice and endorsed by FIGO guidelines. The regimen consists of an initial loading dose of 14 grams administered as follows: 4 grams IV bolus over 5–10 minutes (or 10 mL of 40% solution), followed immediately by 10 grams IM (5 grams in each buttock using 50% solution). This 14-gram loading dose achieves rapid therapeutic serum magnesium levels (4–7 mEq/L) needed to prevent seizures in severe preeclampsia. The subsequent maintenance dose is 5 grams IM every 4 hours for 24 hours postpartum. The Pritchard regimen is preferred in India over the Zuspan regimen (which uses IV infusion) because IM administration is feasible in resource-limited settings and does not require continuous IV access. The mechanism is GABA-mediated CNS depression and reduced acetylcholine release at the neuromuscular junction, raising the seizure threshold. Magnesium sulfate is the only anticonvulsant proven to reduce maternal mortality and morbidity in eclampsia (not phenytoin or diazepam).
Why the other options are wrong
B. 10 grams — This represents only the IM component of the Pritchard loading dose (5 g + 5 g in both buttocks), omitting the critical 4-gram IV bolus. NBE traps students who remember only the IM portion or confuse it with the maintenance dose regimen. 10 grams alone is subtherapeutic and will not achieve adequate serum magnesium levels for seizure prophylaxis. C. 4 grams — This is only the IV loading bolus component of the Pritchard regimen, not the total loading dose. Students who focus on the initial IV administration without understanding the complete two-step protocol (IV + IM) fall into this trap. 4 grams alone is insufficient for seizure prevention in severe preeclampsia. D. 5 grams — This is the maintenance dose given IM every 4 hours after the loading phase, not the initial loading dose. NBE exploits confusion between loading and maintenance dosing—a common error in drug regimen questions. Using only 5 grams initially would fail to rapidly achieve therapeutic magnesium levels.
High-Yield Facts
- Pritchard regimen loading dose: 14 grams (4 g IV + 10 g IM) for seizure prophylaxis in preeclampsia.
- Maintenance dose: 5 grams IM every 4 hours for 24 hours postpartum in the Pritchard protocol.
- Magnesium sulfate is the only anticonvulsant proven to reduce maternal mortality in eclampsia (Magpie trial evidence).
- Therapeutic serum magnesium level: 4–7 mEq/L required for seizure prevention; toxicity occurs >10 mEq/L.
- Pritchard regimen preferred in India over Zuspan (IV infusion) due to feasibility in resource-limited obstetric settings.
- Mechanism: GABA-mediated CNS depression and reduced acetylcholine release at neuromuscular junction.
Mnemonics
Pritchard Loading = 4 + 10 4 grams IV bolus + 10 grams IM (5 + 5 in buttocks) = 14 grams total. Then maintain 5 grams IM Q4H. Use this when dosing magnesium sulfate in preeclampsia. MgSO₄ > Phenytoin/Diazepam Only magnesium sulfate reduces maternal mortality in eclampsia (proven by Magpie trial). Phenytoin and diazepam do not. Remember this for any eclampsia seizure prophylaxis question.
NBE Trap
NBE pairs the Pritchard regimen with individual dose components (4 g, 5 g, 10 g) to trap students who memorize fragments without understanding the complete two-step loading protocol. Confusion between loading dose (14 g) and maintenance dose (5 g) is the primary cognitive error.
Clinical Pearl
In Indian obstetric wards, the Pritchard regimen is preferred because it requires only IM injections and does not depend on continuous IV infusion pumps—critical in peripheral hospitals. A 36-week preeclamptic woman receiving the full 14-gram loading dose will typically have seizure prophylaxis established within 30 minutes, preventing progression to eclampsia.
_Reference: DC Dutta's Textbook of Obstetrics (7th ed.), Ch. 18 (Hypertensive Disorders in Pregnancy); FIGO Guidelines on Management of Hypertensive Disorders in Pregnancy_