Combined effects of diflunisal and nifedipine on uterine contractility in dysmenorrhoeic patients

Effects of calcium channel blockers on the female genital tract

Contractile activity and vascular resistance in the female genital tract are influenced by several smooth muscle tissues with individual mechanisms for control of mechanical activation. Calcium channel blockers have potent relaxant effects on preparations of human myometrium. The myometrial arteries utilize multiple sources of calcium for contractile activation, and excitation-contraction coupling in isolated vessels from non-pregnant uteri seems comparatively less sensitive to nifedipine than in corresponding myometrial preparations. Contractile activation of myometrial and placental arteries at term is inhibited by nitrendipine and nifedipine. Human oviductal smooth muscle depends on superficially bound calcium for mechanical activation, but only phasic contractions can be abolished by nifedipine, while tonic contractions induced by various agents are more resistant to the calcium channel blocker. Menstrual uterine contractions and pain are effectively counteracted by nifedipine in normal and dysmenorrhoeic women. Such therapy may represent an alternative principle in the treatment of dysmenorrhea. Nifedipine has potent relaxant effects on the mid-term pregnant and the post-partum uterus and calcium channel blockers may prove useful in the treatment of premature labor. Nifedipine and related compounds may further show effective in the treatment of pregnancy-associated hypertension. Whether such treatment in late pregnancy involves maintained or even improved placental perfusion could be assumed from in vitro data but needs further studies.

Some extracardiac effects of diltiazem and other calcium entry blockers

Calcium entry blockers have a well documented relaxing effect of smooth muscle, vascular as well as non-vascular. Mainly as a consequence of this action, the drugs have been used for treatment of several non-cardiac disorders where hyperactivity of smooth muscle is considered to have an important role in the pathogenesis. In this short review some of these extracardiac effects of calcium entry blockers are discussed and also their clinical application.

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.

A new look at uterine muscle contraction

Recent progress in our understanding of uterine smooth muscle contraction is reviewed. We no longer believe that actin-myosin interaction in the myometrium occurs through activation of the thin filament; but it is triggered by calcium-dependent phosphorylation of myosin in the thick filament. Calcium is now thought to originate from both extracellular and intracellular sources. Calcium can enter the cell through either a voltage- or a hormone-controlled calcium channel. The intracellular source of calcium is the sarcoplasmic reticulum. The effect of oxytocin in human labor is no longer considered the result of increased circulating oxytocin but rather of increased oxytocin receptors. In contrast, the contractile action of some prostaglandins is related to increased prostaglandin formation at human parturition. The step between hormone binding and cellular action is mediated by second messengers. The uterine-relaxing action of cyclic adenosine monophosphate is now thought to be limited to the inhibition of myosin phosphorylation. Recently discovered second messengers for contraction of the myometrium are phosphoinositides; their turnover causes calcium release from the sarcoplasmic reticulum. Guanine nucleotides are thought to be modulators of these two second messengers.

The effect of a calcium channel blocker (nifedipine) on uterine blood flow in the pregnant goat

The purpose of this study was to analyze the changes in maternal uterine blood flow, maternal arterial blood pressure, and maternal heart rate with the intravenous administration of nifedipine in pregnant, unanesthetized pygmy goats. Bolus injections of 2.5 to 45 micrograms/kg of maternal weight were used. Uterine blood flow did not fall significantly. A transient fall in maternal arterial blood pressure occurred in the first minute after the injection, but the pressure returned to normal after 5 minutes. Maternal heart rate increased immediately after the bolus of nifedipine and returned toward the control value by 30 minutes.

Distribution analysis of intrauterine pressure in nonpregnant dysmenorrheic women

Very few attempts to describe, codify , and implement analysis of intrauterine pressure data have occurred in the past. With a growing interest in intrauterine pressure during dysmenorrhea, the need for new ways of evaluating pressure data have become more acute. The availability of fast, compact microcomputers to process these data provides a tool which may make this goal attainable. In addition to purely mathematical analysis, graphic representations of the changing relationships of pressure and time are also possible. This type of graphic display of data may convey information more rapidly and allow subtle relations to be appreciated more easily. One such display technique, pressure distribution analysis, has been developed and appears to be useful in monitoring dysmenorrhea therapy. The method of the display's development along with examples of its use are presented.

Promising uses of calcium-channel blocking agents

It is not surprising that calcium-channel blocking agents, which have numerous effects on various physiologic systems, have been employed for several "unapproved" uses. This manuscript reviews reports that have appeared within the last two years describing unapproved cardiovascular and noncardiovascular uses of the three available calcium-channel blocking agents. The cardiovascular uses discussed include hypertensive emergencies, pulmonary hypertension, congestive heart failure, aortic insufficiency, Raynaud's phenomenon, migraine headaches, antiplatelet effects and cardiac surgery. Areas of noncardiovascular use include muscular dystrophy, achalasia, esophageal spasm, dysmenorrhea, preterm labor, asthma, hyperuricemia, mania and depression and endocrinologic and oncologic conditions. While some of the data appear promising, other reports are conflicting and contradictory. Furthermore, because much of the information comes from poorly controlled trials or anecdotal reports, even the more promising uses must be studied further and compared with conventional therapy.