Pritchard Regimen for Magnesium Sulfate Administration
The Pritchard regimen consists of a 14-gram loading dose (4 grams IV plus 5 grams IM in each buttock), followed by 5 grams IM every 4 hours in alternating buttocks for 24 hours as maintenance therapy for eclampsia prevention and treatment. 1
Loading Dose Protocol
The loading dose totals 14 grams administered simultaneously through two routes: 1
- 4 grams intravenous - given as initial IV dose
- 10 grams intramuscular - split as 5 grams in one buttock and 5 grams in the other buttock
- All three components together constitute the complete loading dose
Maintenance Dose Protocol
Following the loading dose: 1
- 5 grams IM every 4 hours for 24 hours total duration
- Administer in alternating buttocks with each dose
- Continue for the full 24-hour period unless contraindications develop
Clinical Context and Comparison
The Pritchard regimen is recommended when IV infusion pumps are unavailable or IV access is limited, as it was one of the two protocols validated in the landmark MAGPIE trial that demonstrated approximately 50% reduction in seizure risk. 1, 2
The alternative to Pritchard is the IV-only protocol (4-6 gram IV loading dose over 20-30 minutes, followed by 1-2 grams/hour continuous infusion), which is preferred when IV access and infusion pumps are readily available. 2
Safety Monitoring Requirements
During Pritchard regimen administration, monitor for magnesium toxicity: 3
- Loss of patellar reflexes - first warning sign, occurs at 3.5-5 mmol/L
- Respiratory rate - respiratory paralysis occurs at 5-6.5 mmol/L
- Urine output - magnesium is renally excreted
- Cardiac monitoring - conduction alterations occur above 7.5 mmol/L, cardiac arrest risk above 12.5 mmol/L
Task-Shifting Considerations
In resource-limited settings where only IM administration is permitted by lower-level providers, give 5 grams IM in each buttock (10 grams total) as an emergency loading dose before transfer - it is better to initiate partial treatment than refer without any magnesium sulfate. 1
Duration of Therapy
Standard duration is 24 hours postpartum, though emerging evidence suggests stopping after 8 grams predelivery may be reasonable in select populations with low postpartum eclampsia rates. 2 However, the 24-hour postpartum protocol remains the guideline-recommended standard since eclampsia can occur in the postpartum period. 2