[Effect of co-medication with magnesium sulfate in beta-mimetic tocolysis on parameters of water-electrolyte balance]

With 2 groups of 10 patients the influence of an additional therapy with 1 g magnesium sulfate/h during i.v. tocolysis with the betamimetic fenoterol (2 micrograms/min) upon parameters of water and electrolyte balance has been investigated. The whole of the magnesium administered during the 24 hours investigational period has been eliminated via the kidneys. Most probably due to a competition within the distal tubulus hypermagnesemia was associated with hypocalcemia and hypercalciuria, followed by a rise in parathyroid hormone. As PTH is able to compensate hypocalcemia not only by means of bone mobilisation but also by an increase in enteral Ca absorption, estimated losses of calcium are minimal. These may be neglected, as additional therapy with magnesium sulfate--besides the advantages yet known (cardioprotection, saving of betamimetic dosage, reduction of drug tolerance development)--reduces betamimetic induced water retention, thus significantly diminishing lung edema hazard during tocolytic therapy.