Magnesium Sulphate is the drug of choice for routine anti convulsant management of women with eclampsia, rather than diazepam or phenytoin (The Lancet, 1995) and should be administer in patient with severe pre eclampsia as well. The target of usage is to abort an attack of convulsion, to prevent immediate recurrence of convulsion and to gain time for antihypertensive to function. The role of magnesium sulphate for eclampsia is initially being reported by Lazard and later being popularized by Pritchard.
Magnesium sulphate prevents or controls convulsions by blocking neuromuscular transmission and decrease the amount of acetylcholine secreted at the end plate by the motor nerve impulse
Currently there are three ways to deliver the magnesium sulphate, 1) High dose regimes like Pritchards, 2) Low dose regimes like Zuspan and Single dose regime like VIMS regimes. Whatever the regimes is, delivering the drug intravenously is the most preferred method and the duration of treatment should not normally exceed 24 hours.
The traditional Pritchard's Regime has been used for 55 years since 1955.The Pritchard's regimes involves
4g IV,slow bolus (not less than 3 minutes) followed by 5g IM in each buttock
If convulsion persists over 15 minutes, 2g is given over 2 minutes.
5g IM every 4 hourly at alternate sites. Play particular attention to knee reflex, respiratory rate and urine output.
Meanwhile, Zuspan Regime is given by
4g IV over 5-10 minutes
1-2 g/hr, IV infusion.
Study shows than Zuspan's regime is eight times less effective than Pritchard's regime in the prevention of convulsion in pre eclampsia and eclampsia. Maternal mortality was 2.5 times greater in women who received Zuspan's regimen than among those on Pritchard's regimen. [The Lancet vol 351:9108, 1998].
Even so, current study shows that seizure can be safely controlled in women with eclampsia with a lower dose of MgSO4, with the advantage of a lower magnesium toxicity. It therefore seems that a lower dose of MgSO4 can be safely used at peripheral institutions where facilities for proper monitoring are lacking [Shilva et al, 2007]
In USM the low dose regime is used as follow,
IV MgSO4 4g, slow bolus over 10-15 minutes to prevent cardiac arrest.
IV 1g/hour MgSO4.
If convulsion persist after 15 minutes, a further 2g MgSo4 diluted in 6 ml normal saline or sterile water is given over 15 minutes.
The therapeutic range of magnesium sulphate is 2-4 mmol/l or 4-8 mg/dl. Since the complication is related to the blood level of the magnesium and hazardous, therefore monitoring of the magnesium sulphate toxicity is required. Attention should be paid to patellar reflex, respiratory rate, urine output and pulse oxymetry. Serum magnesium level should be checked when oliguria (<25ml/h), respiratory rate <16/min, Pulse oxymetry <90% and persisting of fitting.
1) Adibah Ibrahim et al, “The Practical Labour Suite Management”, Penerbit Universiti Sains Malaysia, 2009.
2) M.F.M.James, "Magnesium inobstetrics", Best Practice & Research Clinical Obstetrics & Gynaecology 24(2010) 327–337
3) Evidence from the Collaborative Eclampsia Trial, Lancet vol 345: 8963, 1995.
4) Joshi Syyajna D, "MgSO4 regimens in Eclampsia PPT Presentation", 2011, www.suyajna.com
5) Shikha Seth, Arun Nagrath & Dinesh Kumar Singh, "Comparison of low dose, single loading dose, and standard Pritchard regimen of magnesium sulfate in antepartum eclampsia", Anatol J Obstet Gynecol 2010; 1: 1, Alkim Basin Yayin.
6) Shilva, Saha SC, Kalra J, Prasad R, "Safety and efficacy of low-dose MgSO4 in the treatment of eclampsia", Int J Gynaecol Obstet. 2007 May;97(2):150-1.
7) Lelia Duley, "Evidence and practice: the magnesium sulphate story", Best Practice & Research Clinical Obstetrics and Gynaecology, Vol 19 No 1, 2005, Elsevier