Risk-benefit assessment of tocolytic drugs.

beta 2-Mimetics are the principal agents used for myometrial relaxation. As all the available drugs also have beta 1-stimulant effects, the various side effects (cardiovascular, pulmonary and metabolic) require a critical consideration of the clinical indications, thorough supervision and combined therapeutic concepts. With regard to clinical indications, 'prophylactic tocolysis' frequently turns out to be unnecessary, as does the treatment of physiological uterine contractions during pregnacy which have no effect on the cervix. The benefit of tocolysis must be seen not so much in a reduction of preterm labour but in enabling the obstetrician and neonatologist to optimise the handling of the premature baby, e.g. by allowing lung maturation or by enabling the patient to reach a centre for perinatal medicine before the birth. Labour-dependent fetal distress situations during birth at term can also be managed successfully. Supervision involves thorough control of both mother (especially of cardiovascular and metabolic parameters, electrolyte and water balance) and fetus (cardiotocography, fetometry) in order to decide individually when possible benefits are outweighed by maternal or fetal risks. Combination of beta 2-mimetic treatment with magnesium therapy reduces the beta-mimetic dosage required, has a cardioprotective action, and reduces the development of drug tolerance and the risk of lung oedema. This combination, therefore, should become routine in tocolytic therapy. If further protection against cardiovascular and risk of lung oedema is required, administration of beta 1-blockers is advisable.