Possible treatment of pre-eclampsia with calcium channel blocking agents

Magnesium taurate for the prevention and treatment of pre-eclampsia/eclampsia

The use of parenteral magnesium sulfate for the management of pre-eclampsia/eclampsia is well established. In striking analogy to the effects of hypermagnesemia, taurine has antivasospastic, antihypertensive, platelet-stabilizing, anticonvulsant and hypoxia-protective properties. Thus parenteral magnesium taurate can reasonably be proposed as a superior alternative to magnesium sulfate in the treatment of pre-eclampsia; administered orally as a component of prenatal supplementation, magnesium taurate might well have both preventive and therapeutic value in this syndrome. In the light of the hypoxia-protective actions of both magnesium and taurine, such supplementation might also protect fetuses experiencing temporary perinatal asphyxia, lessening the risk of cerebral palsy.

Comparison of the anticonstrictor action of dihydropyridines (nimodipine and nicardipine) and Mg2+ in isolated human cerebral arteries

The isometric tension recorded from ring segments of branches of human middle cerebral artery was the parameter used to study the inhibition of spasmogen-induced contractions as model for cerebral vasospasm. Concentration-response curves to 5-hydroxytryptamine (10(-9)-3 x 10(-5) M) and prostaglandin F2 alpha (10(-7)-3 x 10(-5) M) were inhibited in Ca(2+)-free medium and in Ca(2+)-free medium to which EGTA (1 mM) had been added, respectively. Nimodipine (10(-7), 10(-5) M), nicardipine (10(-7), 10(-5) M) and Mg2+ (magnesium sulfate 10(-4), 10(-2) M) inhibited the 5-HT-elicited contractions, and this inhibition was similar for the highest concentrations tested. In contrast, nimodipine and nicardipine were more effective than Mg2+ to inhibit the prostaglandin F2 alpha-elicited contractions. Nimodipine (10(-9)-10(-5) M), nicardipine (10(-9)-10(-5) M) and Mg2+ (10(-5)-3 x 10(-2) M) relaxed the arteries precontracted with PGF2 alpha (10(-5) M), but nicardipine was the most potent relaxant drug. Because 5-hydroxytryptamine and prostaglandin F2 alpha may be involved in the pathogenesis of cerebral vasospasm, nimodipine, nicardipine, and Mg2+ could be used in the pharmacological treatment of this disorder. However, dihydropyridines (particularly nicardipine) are more potent anticonstrictors than Mg2+.

Antihypertensive drug effects on placental flow velocity waveforms in pregnant women with severe hypertension

Doppler studies of the uterine and umbilical arteries were performed in 24 acutely hypertensive pregnant women. Women were divided into 2 groups: Group 1 (diastolic blood pressure (DBP) > 110 mm Hg) received placebo (n = 6) or 10 mg oral nifedipine (n = 9); Group 2 (DBP > or = 110 mm Hg) received 10 mg oral nifedipine (n = 5) or 10 mg intravenous hydralazine (n = 4). Treatment allocations were random within groups and the investigator and patient were blind to the treatments. Baseline flow velocity waveforms (FVW) and posttreatment FVW's at 30, 60 and 120 minutes were recorded. There was no significant difference between baseline and posttreatment FVW indices within or between groups. Placebo was as effective as nifedipine in lowering blood pressure over 2 hours of study. There were no significant adverse effects of treatment.

The effects of nifedipine on pregnancy outcome and morphology of the placenta, uterus, and cervix during late pregnancy in the rat

OBJECTIVE

Although the calcium antagonist nifedipine has been reported to suppress preterm labor, little is known of the effects of long-term nifedipine use in late pregnancy. In this study the effects of nifedipine on pregnancy outcome and the morphologic features of the reproductive tract in the late-pregnant rat were investigated.

STUDY DESIGN

From days 14 to 21 of gestation pregnant rats were administered three or 30 times the maximum human dose of nifedipine reported to suppress preterm labor. Analysis was performed on day 21.

RESULTS

Blood vessel dilatation, increased vascularization of the uterus and placenta, and trophoblast hypertrophy were seen in both nifedipine-treated groups. Placental weight was increased in the higher-dose group, but neither dose of nifedipine resulted in any change of fetal survival or malformations. Pup weight was not different from that of controls in the lower-dose group but was significantly reduced (p less than 0.001) with the higher dose. Histologic changes in uterine musculature and cervical collagen were consistent with the inhibitory effects of nifedipine on uterine contractions.

CONCLUSION

The results suggest that, in addition to tocolysis, nifedipine can cause vascular dilatation in both the uterus and the placenta. The use of nifedipine within the normal dose range does not appear to adversely affect fetal outcome and may potentially improve fetal outcome in some disorders of pregnancy.

In vivo and in vitro effects of magnesium sulfate in the cerebrovascular bed of the goat

The effects of magnesium sulfate in the cerebrovascular bed were studied both in vivo, by measuring cerebral blood flow in conscious nonpregnant goats, and in vitro, by recording isometric tension in isolated goat middle cerebral arteries. Injections of increasing doses (10 to 300 mg) of magnesium sulfate directly into the cerebral circulation elicited transient and dose-dependent increases in cerebral blood flow and decreases in cerebral vascular resistance. Similar results were obtained when increasing doses (0.3 to 3 gm/15 min) of magnesium sulfate were infused intravenously, although the vasodilatations reached a stable plateau that remained when the infusions finished. Cumulative addition of magnesium sulfate (10(-5) to 3 x 10(-2) mol/L) did not change the isometric tension of isolated arterial segments at resting tone, but relaxed in a concentration-dependent manner the arterial segments preconstricted with 10(-5) mol/L prostaglandin F2 alpha. These results demonstrate that magnesium sulfate acts as a dilator in the cerebral circulation by acting directly on the cerebral arteries. This could explain, at least in part, its beneficial effects on preeclampsia-eclampsia.

Magnesium sulfate reverses experimental delayed cerebral vasospasm after subarachnoid hemorrhage in rats

We induced experimental delayed cerebral vasospasm by the intracisternal injection of greater than 0.5 ml blood in 30 rats. Seventy-two hours later the basilar artery was exposed via the transclival approach and photographed at high-power magnification through an operating microscope. We then evaluated the effect of topical (n = 30) and intravenous (n = 20) magnesium sulfate on the spastic artery by computerized image analysis. A greater than 50% reduction in baseline diameter of the basilar artery was observed in the rats subjected to subarachnoid hemorrhage compared with the 10 controls (p less than 0.0001). Intravenous magnesium sulfate dilated the spastic artery to approximately 75% of the baseline diameter in control rats (p less than 0.0001). Topical magnesium sulfate caused dramatic dilation of the basilar artery in both the control and the subarachnoid hemorrhage groups to near 150% of the baseline diameter in the controls (p less than 0.001). All rats receiving intravenous magnesium sulfate reached therapeutic plasma levels of the ion. Hemodynamic effects were mild and immediately reversible upon cessation of magnesium sulfate administration. We suggest that magnesium has a role in the treatment of subarachnoid hemorrhage-induced vasospasm in humans.

Action of magnesium sulfate in the treatment of preeclampsia-eclampsia

Recent evidence supports the concept that cerebral vasospasm is involved in the pathogenesis of eclampsia. Magnesium, which has a beneficial effect in eclampsia, may act by opposing calcium-dependent arterial constriction, thereby relieving vasospasm. Magnesium may also antagonize the increase in intracellular calcium concentration caused by ischemia and thus prevent cell damage and death. Magnesium might have a role in the treatment of cerebral vasospasm and ischemia, such as occurs in subarachnoid hemorrhage, ischemic stroke, and brain trauma.