Research report: Faculty of Health Sciences / ABSTRACT Labour induction in an underresourced environment poses a tremendous challenge. While labour induction is a common obstetric procedure, it poses potential hazards for mother and fetus. This is largely dependent on method and agent used and can be expensive on limited resources because of high purchase prices, refrigerated storage, monitoring equipment and manpower. Misoprostol is a unique anti-ulcer agent that has good properties as an induction agent, but as yet not fully evaluated. It is relatively cheap, easily available, simple to store and has a long shelf life, and would amount to considerable cost saving in an underresourced setting if it were proven to be effective and safe for induction of labour. A simple reliable method of administration and appropriate dosage regimen of misoprostol for the purposes of induction of labour is needed. This study was undertaken in two phases; Part A. The clinical trial where an oral misoprostol suspension was given in a stepwise manner for the induction of labour alone or in combination with an inexpensive mechanical method (Foley catheter bulb) is compared with the “standard” method of induction i.e. dinoprostone 2 mg gel in a randomized controlled trial. Altogether 750 patients (250 in each arm) were recruited. Part B. (a) In vitro study to verify if misoprostol has a direct stimulatory effect on gut smooth muscle similar to sihlambezo.1 There is an increase in the incidence of meconium stained liquor in women who have taken sihlambezo or castor oil and misoprostol.2 It is postulated that misoprostol crosses the placenta and stimulates foetal bowel activity directly rather than as a result of asphyxia caused by excessive uterine contractions due to misoprostol. Strips of rat uterine and intestinal smooth muscle were mounted on a strain gauge with a chart recorder in a physiological bath as was done in the Pharmacology department for the original sihlambezo studies. The model was perfused with doubling concentrations of each test substance, and the concentration noted at which the first uterine muscle and the first bowel muscle activity was detected. The test substances were: #1; prostaglandin E2 (Dinoprostone) #1; oxytocin (Syntocinon) #1; misoprostol freshly dissolved in water #1; misoprostol freshly dissolved in a weak hydrochloric acid solution to approximate stomach content pH #1; misoprostol dissolved in water and stored for 2 hours, 6 hours, 24 hours and 1 year. For each substance, the ratio between the minimum stimulatory concentration for uterine to bowel smooth muscle was calculated, and these ratios compared between substances. The absolute minimum stimulatory concentrations were compared between the different misoprostol preparations to determine the effects of storage and acidification. (b) In vitro study to find out if misoprostol dissolved in water is stable and over what duration of time. This has practical importance, because if it is unstable, it may imply that a fresh sample has to be prepared each time the induction agent is given, and this may be several times per patient per induction. This would escalate the cost of the drug, especially in an underresourced setting such as ours, and would mean more manpower i.e. nursing staff, would be required for each case of induction. We also wanted to establish if acidification of the preparation would affect misoprostol stability as was implied to happen when misoprostol is given vaginally3. References 1 Mitri F, Hofmeyr GJ, van Gelderen CJ. Meconium during labor, self medication and other associations. S Afr Med J 1987: 71: 431-433. 2 Hofmeyr GJ, Gulmezoglu AM. Vaginal misoprostol for cervical ripening and labor induction in late pregnancy (Cochrane Review). In: The Cochrane Library, Issue 3, 1999. Oxford: Update Software. 3 Gunalp S, Bildirici I. The effect of vaginal pH on the efficacy of vaginal misoprostol for induction of labour. Acta Obstet Gynaecol Scand 2000; 79(4): 283-5.