Influence of Tocolytical Medications on Hemodynamics (Central and Peripheral) and Vascular Function in a Pilot Study to Determine the Design of the Final Study and the Final Study Itself

This trial will consist of two parts: A pilot study in a three-way cross over trial to determine the highest well tolerated dose of Ritodrine (Pre-Par®), the impact of Atosiban (Tractocile®) on the hemodynamics and hence the design of the final study. The final study is planned as a three-way crossover trial to investigate and compare the cardiovascular effects of Ritodrine, Atosiban and placebo to relate those effects to the pharmacokinetics of Ritodrine and Atosiban (PK/PD modelling).