The in vitro antiplasmodial activity of crude extracts from the leaves and twigs of five plant species used traditionally in Benin for the treatment of malaria was assessed against the 3D7 chloroquine-susceptible strain of Plasmodium falciparum. Their selectivity was evaluated on J774 macrophage-like murine cells and WI38 human normal fibroblasts. For each species, methylene chloride, methanol and aqueous extracts were tested. The best inhibition of the growth of Plasmodium falciparum was observed with the methylene chloride extracts of Strychnos spinosa leaves (IC50=15.7µg/ml) and Canthium setosum leaves and twigs (IC50=31.2 and 14.3µg/ml, respectively). All these extracts had a low cytotoxicity. These results confirmed the good antiplasmodial activity of the methylene chloride extract of the aerial parts of C. setosum [1]. No data were available on S. spinosa leaves as only stems and barks were studied up to now and did not show any activity [2,3].

Reinvestigation of Strychnos usambarensis Gilg resulted in the isolation of a tertiary phenolic bisindole alkaloid, 10'-hydroxyusambarensine (1), which was identified by detailed spectroscopic methods. Compound 1 was moderately active against two strains of Plasmodium falciparum in vitro.

The development of new drugs requires increasingly the performance of large multinational clinical trials (MCT) with a common protocol. They must be planned when the demonstration of a hypothesis, which requires specific conditions (for example availability of patients with rare diseases, a particular infrastructure or expert knowledge in trial centers) has to be proven in an acceptable time. Our own experience has shown that such multinational trials are more time-consuming in their preparation and their analysis than multicenter trials which are run in one country. MCTs are associated with complex problems due to many differences in medical culture, treatment strategies, administrative guidelines, etc., between countries. When possible MCTs should be realized in countries and centers with relatively similar medical practices. A global coordination is necessary to control the progress of the trial in the different countries. The major requirements for the successful realisation of an MCT, from the writing of the first draft of the protocol until the publication of the results, are a well-coordinated multidisciplinary team and an effective project management.

In developing countries, severe vitamin A deficiency is associated with increased child mortality. In Kivu, Zaïre, child mortality rate is approximately 50 per 1000 per year and protein calorie malnutrition is endemic. To evaluate vitamin A status in this population, we measured plasma retinol levels in 28 severely malnourished hospitalized children (plasma albumin level below 3 g/dl), and in 153 outpatients (mean plasma albumin level: 3.19 +/- 0.7 g/dl) as controls. Sixty percent of inpatients and 37 percent of out-patients had retinol levels below 10 micrograms/dl (P = 0.02) suggesting a high prevalence of severe vitamin A deficiency in this population. We found that plasma retinol levels were correlated with low retinol binding protein plasma levels (r = 0.77). We conclude that although vitamin A deficiency probably exists in this malnourished population, low retinol levels could at least partly be related to decreased levels of its carrier protein.

The review describes gastrointestinal receptors which are of therapeutic interest for the treatment of motility disorders. It updates the present knowledge on muscarinic, adrenergic, dopamine, opioid and dihydropyridine receptors, their subtypes, cellular sites and functional role as drug targets. On the basis of this pharmacological receptor concept, drugs like bethanechol, clonidine, lidamidine, metoclopramide, domperidone, cisapride, loperamide and nifedipine are evaluated in proven and potential indications. In view of the very complex regulation of motility, our understanding of receptors is still fragmentary and our tools to treat motility disorders do not fulfil all therapeutic requirements. This review tries to point out the areas of particular need for further basic research and the prospects of further drug development.

The study is of double-blind crossover design. In the first part of the study, rioprostil (300 micrograms and 600 micrograms) is given orally with a solid breakfast to 9 healthy male volunteers. Both doses of rioprostil delay and reduce the 3-h postprandial GIP release. They also reduce the maximal postprandial insulin concentration, but only rioprostil (600 micrograms) reduces the 3-h integrated release of insulin significantly (by approximately 20%). Neither dose modifies the postprandial glucose gastrin levels significantly. In another study two groups of 6 volunteers are studied in parallel; they are given either rioprostil (600 micrograms) or a placebo each evening for 14 days. On the mornings before and on days 13 and 14 of the study the volunteers take a solid breakfast and blood glucose is measured 1 h and 2 h postprandially. The results show that no differences in the basal and postprandial glucose levels are observed. In conclusion, rioprostil given with a meal can reduce the insulin release but it does not change the postprandial blood glucose levels when given as a single dose or repeatedly in an evening dose. This study shows that rioprostil can be given to patients with diabetes.

When administered as 300 micrograms b.d. or as 600 micrograms once in the evening, the new prostaglandin E1 analogue, rioprostil, is capable of reducing nocturnal H+ activity (1200 h to 0800 h) by 52% and 74%, respectively (p less than 0.01). Diurnal acidity (0900 h to 1800 h), on the other hand, is only reduced by 33% and 15% (not significant). A single evening dose of rioprostil, 600 micrograms, is used successfully on 208 patients suffering from acute duodenal ulcer. After 2 weeks and 4 weeks of treatment, the healing rates are comparable to the high values obtained with ranitidine, 300 mg nocte (rioprostil, 600 micrograms nocte: 54.1% and 84.1%; ranitidine, 300 mg nocte: 54.4% and 89.9%). There are also no significant differences between the groups as regards symptomatic improvement. Severe diarrhoea and abdominal complaints do not occur with rioprostil, 600 micrograms nocte.

A single oral dose of rioprostil, a synthetic methyl-prostaglandin E1, together with or 2 h before ingestion of 0.8 mg beta-acetyldigoxin significantly delays the rate but does not change the extent of beta-acetyldigoxin absorption. However, repeated evening doses of rioprostil do not alter either the glycoside steady-state plasma levels or renal excretion.

Numerous clinical studies have been performed to establish efficacy and safety of drugs in gastroenterological disorders. Only in a few if any of these studies, however, the rationale for the optimal dose and the dose regimens, respectively, have been addressed. Adequate and well-controlled dose finding studies play a key role in the clinical assessment of new drugs and in the evaluation of new indications. Hereby the range from the minimal effective dose to the maximal effective and well tolerated dose can be assessed and thus the optimal dose-range and dosage regimen be determined. Meaningful pharmacodynamic studies can be performed in the gastrointestinal tract also in healthy volunteers provided that a method with a high predictability for the desired therapeutic effect is available such as measurement of gastric acid secretion and its inhibition by a drug. Dose finding studies in gastroenterology can be carried out under two main aspects: First, to assess the pharmacodynamic and therapeutic effect of a compound on the gastrointestinal tract (e.g. anti-ulcer drug). Second, to evaluate the side effects of a drug on the gastrointestinal tract (e.g. gastric mucosal damage by non-steroidal anti-inflammatory drugs). For the evaluation of new drugs in gastrointestinal therapy a number of methods are available which yield accurate and reproducible data. While careful clinical-pharmacological dose-response studies using these methods have been carried out already more than a decade ago, it is surprising that therapeutic dose finding studies have become available only during the past few years. For scientific as well as for ethical reasons more trials which determine the optimal therapeutic dose are warranted.

Nervous control of gastrointestinal motility is extremely complex, is regulated by the enteric system, the "brain of the gut", and modulated by extrinsic nerves. This system with its multiplicity of transmitters and receptors does not always allow a clear interpretation of experimental data, especially with compounds lacking specificity. In this review the complex situation is described particularly in relation to receptor populations (cholinergic, adrenergic, dopamine, histamine, 5-hydroxytryptamine, opioid, gamma-aminobutyric acid (GABA), prostanoid and dihydropyridine receptors), therapeutic aspects of drugs and their usefulness in children. Newer principles with known drugs and promising new compounds with a more appropriate kinetic or fewer side-effects, deriving from distinct pharmacological groups, as candidates for the treatment of gastrointestinal disorders are considered e.g. anticholinergics (prifinium or actilonium bromide), adrenergic alpha 2-agonists (clonidine, lidamidine) for diarrhoea in diabetic neuropathy, adrenergic beta-blockers for shortening postoperative ileus (propranolol), dopamine receptor antagonists (metoclopramide, domperidone, alizapride) and another prokinetic substance (cisapride) which may be useful for a number of applications as gastro-oesophageal reflux, gastro-paresis, intestinal pseudo-obstruction, cystic fibrosis and constipation, morphine derivatives (e.g. loperamide) for intractable diarrhoea and calcium antagonists (e.g. nifedipine) for achalasia. Increasing experience in digestive tract pharmacology and reliable clinical studies will furthermore be the basis for a more specific and better tolerated therapy of gastrointestinal motility disorders in adults and children.

To investigate the effect of aclatonium napadisilate (Ac), a synthetic cholinergic compound, on human interdigestive gastrointestinal function, six healthy volunteers underwent gastrointestinal intubation for measurement of duodeno-jejunal motor activity and pancreatic enzyme secretion. Each subject was studied twice on two separate days and received either aclatonium (300 mg) or placebo intraduodenally in randomized order. Aclatonium significantly increased the overall length of the cycle of interdigestive motor complex (IMC) by a mean of 34% (p<0.05) without stimulating the phases of increased motor activity. Aclatonium slightly, but significantly increased output of lipase during phase II of the IMC (p<0.05), whereas outputs during phase I and III were not significantly changed. We conclude that aclatonium in a dose of 300 mg has only weak cholinergic effects on motility and exocrine pancreatic secretion in healthy humans during the interdigestive state.

The antisecretory effect of rioprostil on acid and pepsin secretion stimulated by pentagastrin or a meal, or on the 24-h intragastric acidity is tested in four different studies in 33 healthy male volunteers using a double-blind, crossover design. The oral doses of rioprostil used are 50 micrograms, 100 micrograms, 150 micrograms, 200 micrograms, 300 micrograms and 600 micrograms; these are the results obtained: Rioprostil reduces basal H+ and pepsin output by more than 50%. Rioprostil, 300 micrograms and 600 micrograms, significantly reduces the 3-h pentagastrin-stimulated acid output by 43.5% and 58.9%, respectively, and the 3-h stimulated pepsin output by 41.1% and 66.5%, respectively (p = 0.01). Depending on the method used for intragastric titration the following percentages of inhibition of acid secretion are observed, 40%, 65%, and 75% with 150 micrograms, 300 micrograms, and 600 micrograms rioprostil respectively, with one method and 32%, 34%, and 79% with 25 micrograms, 50 micrograms, and 200 micrograms rioprostil respectively, with a somewhat modified technique. The differences observed in % inhibition between these two studies can be explained by the use of a different intragastric titration technique. Rioprostil, 300 micrograms and 600 micrograms, significantly inhibits night-time acid secretion (AUC x h, 2400 h-0800 h) by 52% and 73.5% when compared with placebo (p = 0.03). The calculated ED50 for acid inhibition is 86.5 micrograms of rioprostil.

The influence of rioprostil on the resting pressure of the lower esophageal sphincter (LESP) and on the bolus-stimulated contraction wave amplitude of primary peristalsis was investigated in 9 healthy male volunteers receiving placebo or 300 and 600 micrograms of rioprostil orally in a randomised, double-blind, threefold cross over study. Manometry was performed using the low-compliance pneumohydraulic infusion system. Rioprostil in a dose of 600 micrograms slightly increased LESP and contraction wave amplitudes measured 5 cm and 10 cm above LES. The duration of the peristaltic contractions was not altered. We conclude that rioprostil in doses which inhibit effectively gastric acid and pepsin secretion and heal peptic ulcers has no inhibitory effects on esophageal motility. Thus rioprostil may be a candidate to treat reflux esophagitis and studies are warranted to establish its efficacy.

Following abdominal radiation, a 16-year-old male developed persistent vomiting, metabolic alkalosis, and cachexia secondary to gastric stasis, atony, and dilatation in the absence of mechanical obstruction. Fluoroscopically and manometrically, antral motility was found to be severely impaired. Antral motor activity was not influenced by metoclopramide, but stimulated by carbachol. During oral maintenance carbachol therapy, gastric emptying of food was restored and sufficient oral nutrition could be resumed. The improvement persisted even after termination of therapy four months later. Systematic investigations on the effects of abdominal radiation on gastrointestinal motility appear to be necessary.

The protective effect of 50 and 100 micrograms of the synthetic prostaglandin E1 analogue rioprostil (2-decarboxy-2-hydroxymethyl-15-deoxy-16RS-hydroxy-16-methyl PGE1) against the 0.5 and 1 g acetylsalicylic acid (ASA)-induced changes of gastric potential difference (PD) was compared to that of placebo in a double-blind cross-over study in 8 volunteers. Rioprostil 50 and 100 micrograms reduced significantly (p = 0.45) the intensity (area under baseline) of the 0.5 g ASA-induced PD changes. Both doses reduced highly significantly (p = 0.003) the time taken for PD to return to baseline value (15.1 min with 50 micrograms and 17.2 min with 100 micrograms rioprostil vs 43.5 min with placebo). Both doses of rioprostil also reduced significantly (p = 0.04) the PD maximal drop induced by 1 g ASA and reduced highly significantly (p = 0.006) the time taken for PD to return to baseline value (18.9 min with 50 micrograms and 16.8 min with 100 micrograms rioprostil vs 64.6 min with placebo). This study shows that rioprostil protects the stomach against the ASA-induced alterations of the gastric mucosa even when it is given at the same time as ASA and in doses which have only a small antisecretory effect.

On different days, fasted volunteers were given either 100 ml of ethanol (40% v/v), glucose (isocaloric to ethanol) or distilled water intragastrically; the instillations always starting during the first observed duodenal phase I of the interdigestive migrating complex (IMC). Both ethanol and glucose produced a fed pattern of motility but only glucose significantly (P less than 0.05) delayed the reappearance of a new duodenal phase III of the IMC when compared to water. Ethanol and glucose significantly increased the 1-h duodenal bicarbonate output 7- and 16-fold, respectively. Glucose, but not ethanol, stimulated the duodenal amylase output when compared to water. Glucose, but not ethanol, caused a significant rise in plasma gastrin concentration; plasma secretin levels not being altered by both substances. We conclude that in non-alcoholic humans, an intragastric administration of ethanol in a concentration present in whisky and in an amount that is consumed in ordinary social drinking has a weak stimulatory action on pancreatic bicarbonate secretion and that this action is not mediated by release of secretin.