Following intramuscular administration the onset of action is about one hour and lasts for three to four hours. Magnesium is excreted solely by the kidneys at a rate proportional to the plasma concentration (concentration in the blood) and glomerular filtration (rate at which the blood is filtered through the kidneys). Magnesium sulfate is associated with several minor side effects; serious side effects are uncommon, occurring at elevated magnesium serum concentrations greater than 7.0 mEq/L. Serious toxicity can be counteracted with calcium gluconate.Even with therapeutic serum magnesium concentrations, recurrent convulsions may occur, and additional magnesium may be needed, but with close monitoring for respiratory, cardiac, and neurological depression. If magnesium administration with resultant high serum concentrations fails to control convulsions, the addition of other intravenous anticonvulsants may be used and  intubation and mechanical ventilation may be initiated. It is important to avoid magnesium toxicity, including thoracic muscle paralysis, which could cause respiratory failure and death. Magnesium sulfate results in better outcomes than diazepam, phenytoin or a combination of chlorpromazine, promethazine, and pethidine. Blood pressure management
Blood pressure control is used to prevent stroke, which accounts for 15 to 20 percent of deaths in women with eclampsia. The agents of choice for blood pressure control during eclampsia are hydralazine or labetalol. This is because of their effectiveness, lack of negative effects on the fetus, and mechanism of action. Blood pressure management is indicated with a diastolic blood pressure above 105–110 mm Hg.
Delivery
If the baby has not yet been delivered, steps need to be taken to stabilize the woman and deliver her speedily. This needs to be done even if the baby is immature, as the eclamptic condition is unsafe for both baby and mother. As eclampsia is a manifestation of a type of non-infectious multiorgan dysfunction or failure, other organs (liver, kidney, lungs, cardiovascular system, and coagulation system) need to be assessed in preparation for a delivery (often a caesarean section), unless the woman is already in advanced labor. Regional anesthesia for caesarean section is contraindicated when a coagulopathy has developed. There is limited to no evidence in favor of a particular delivery method for women with eclampsia. Therefore, the delivery method of choice is an individualized decision. Monitoring
Invasive hemodynamic monitoring may be elected in an eclamptic woman at risk for or with heart disease, kidney disease, refractory hypertension, pulmonary edema, or poor urine output. Etymology
The Greek noun ἐκλαμψία, eklampsía, denotes a "light burst"; metaphorically, in this context, "sudden occurrence." The New Latin term first appeared in Johannes Varandaeus’ 1620 treatise on gynaecology Tractatus de affectibus Renum et Vesicae. The term toxemia of pregnancy is no longer recommended: placental toxins are not the cause of eclampsia occurrences, as previously believed. Popular culture
In Downton Abbey, a historical drama television series, the character Lady Sybil dies (in series 3, episode 5) of eclampsia shortly after child birth.