During animal experiments two substances, which are used for tocolysis (Fenoterol and Clenbuterol) have been compared regarding their tocolytic efficiency (determinations of myometrial cyclic AMP after long term treatment of the pregnant rat), their effects upon myocardial high energy phosphates (determinations of maternal myocardial high energy phosphates as well as of maternal and fetal myocardial cyclic AMP after long term treatment of the pregnant rat) and upon the hemodynamic situation (acute experiments with thoracotomized dogs). While significant hemodynamic derangements could be stated when using Fenoterol, no significant evidence for such alterations could be found during Clenbuterol administration during acute experiments. Determinations of myocardial high energy phosphates however reflected an augmented myocardial workload, both after Fenoterol and Clenbuterol administration. As by means of myometrial cyclic AMP determinations Clenbuterol proved to be at least as efficient as Fenoterol, concerning the tocolytic effect, Clenbuterol can be recommended as an oral tocolytic because of its pharmaco-cinetic advantages and the encouraging results from our hemodynamic investigations. According to results from chronical experiments an additional cardioprotection by means of magnesium substitution and eventually beta 1-blockade is still recommended.

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[Magnesium aspartate as a cardioprotective agent and adjuvant in tocolysis with betamimetics. Animal experiments on the kinetics and calcium antagonist action of orally administered magnesium aspartate with special reference to simultaneous vitamin B administration].

With pregnant Wistar-rats, suffering from alimentary magnesium deficiency, absorption and distributing of Mg28 has been studied, the latter having been applied as aspartate and as chloride, with and without simultaneous substitution of vitamin B6. Absorption and tissue pooling were found to be augmented when using the aspartate and even more when adding vitamin B6. These differences were significant in the blood as well as in fetal and myocardial tissue. Correlation between blood-Mg28 und Mg28-activities in various tissues shows, that blood magnesium levels indicate a magnesium deficiency at least in the tissues of interest: fetus, myocardium, uterus and placenta. Nevertheless blood magnesium levels fail to reflect an additional tissue pooling, that exerts a beneficial action in the respect of cardio protection and of saving beta-mimetic tocolytics. When measuring magnesium and calcium excretion during chronic experiments with and without oral magnesium aspartate substitution, it could be demonstrated, that the amount of substituted magnesium has been pooled almost totally. Oral magnesium substitution furthermore reduces intestinal calcium absorption. Investigation on calcium uptake into the maternal myocardium revealed, that oral magnesium aspartate substitution significantly diminishes myocardial calcium uptake, the latter among others being responsible for cardiac hazards during tocolysis with beta-mimetic substances, while the pharmacologic calcium-antagonist Verapamil failed to do so.

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