Drugs used in the management of toxemia of pregnancy

The role of calcium channel blockers in the treatment of women with preeclampsia

Preeclampsia was originally known as a process whereby an unknown “toxin” was responsible for a variety of responses. While this toxin has yet to be determined, many theories have prevailed as to the appropriate therapy for this condition.

Recently, antihypertensive therapy has become increasingly regarded as an important component of the medical management of women with preeclampsia. Initially, the ideal therapy for peripartum acute hypertensive emergencies was felt to be a smooth muscle relaxant and the most commonly prescribed agent was hydralazine. This drug was felt to be beneficial because of its action on vascular smooth muscle, decreasing vasospasm. Outside of the United States diazoxide was also used for this purpose, although this drug has been replaced because of the high incidence of fetal distress. Another agent that was frequently used was α-methyldopa which was initially considered to be the treatment of choice in the treatment of patieats with moderate and severe preeclampsia. Recently, α-methyldopa has been reserved for the outpatient management of gestational hypertension, especially in women with mild preeclampsia or chronic hypertension.

Treatment of preeclampsia with prostaglandin A1

The vasodepressor prostaglandin A1 appeared to offer a major clinical potential solution in cases of severe pregnancy-induced hypertension. Thirty pregnant women with severe pregnancy-induced hypertension and a low Bishop score were studied in three equal groups. Group 1 received prostaglandin A1 infusions alone (0.5 microgram/kg/min for a maximum of 24 hours). Group 2 had received initial priming by prostaglandin E2 vaginal gel 6 hours before the onset of the prostaglandin A1 infusion, and group 3 was treated by conventional therapy and oxytocin induction. In the first two groups blood pressure was reduced to normotensive values, and labor was induced satisfactorily in 15 of the 20 cases, but four patients in group 1 were delivered within 24 hours after infusion. Group 2 offered the most favorable results because 80% were delivered during the infusion; thus the postinfusion rebound rise in blood pressure was avoided. Group 3 presented the least acceptable results, with the highest failure rate and an increased number of operative deliveries.

Maternal and fetal cardiovascular indices during fetal hypoxia due to cord compression in chronically cannulated sheep. I. Responses to timolol

Timolol, one of the newer beta-adrenergic antagonists, has less depressive effects on the heart than propranolol, so that it has the potential for use by pregnant women. In chronically cannulated ewes, timolol at 0.01 and 0.1 mg/kg of body weight induced maternal and fetal bradycardia; the higher dose also depressed uterine blood flow and fetal PaO2. When this higher dose preceded brief compression of the umbilical cord, uterine flow was further depressed and the usual posthypoxia rebound tachycardia did not develop. Both the blocking of fetal responses to hypoxia (precluding detection of fetal distress) and the reduction in uterine flow led us to conclude that timolol taken by a mother could pose particular hazards for her fetus in hypoxic conditions, such as during cord compression at parturition.

Placental transfer of etozolin and ozolinone during the first half of gestation in man

The placental transfer of etozolin and its pharmacologically active metabolite ozolinone was studied in 48 patients during the first (44 patients) and second (4 patients) trimester. 24 patients received a single oral dose of etozolin 400 mg 2-20 h prior to interruption of pregnancy by curettage or prostaglandin infusion. 24 other patients received 3 oral doses of etozolin 400 mg (11 patients) or 800 mg (13 patients) on 3 consecutive days, and pregnancy was terminated 2-10 h after the last dose. The fetal tissue/maternal serum and placental tissue/maternal serum ratios of etozolin and ozolinone were found to lie between 0.3 and 0.6. The serum levels were lower in pregnant than in non-pregnant patients. The low placental and fetal concentrations of etozolin and ozolinone suggest that these drugs may prove useful when a diuretic is indicated in the treatment of oedema and hypertension during pregnancy.

The treatment of hypertension in pregnancy

The drug treatment of hypertension occurring during pregnancy is described. Diagnostic problems and management are outlined, and the available literature regarding the use of standard hypotensive agents in pregnancy is reviewed by drug class. Based on currently published literature and opinion, the following drugs are recommended when needed during pregnancy (with proper monitoring) : methyldopa, hydralazine, and furosemide. Caution is recommended when the following drugs are used during pregnancy: propranolol, and thiazide diuretics. The following drugs are not recommended for use during pregnancy based on currently available information: reserpine, clonidine, chlorthalidone, prazosin, minoxidil, spironolactone, ethacrynic acid, metoprolol, nadolol, and guanethidine.