Ability of nifedipine to prolong parturition in rats.
Rats were randomly assigned to treatments: (i) no surgery control; (ii) saline control; (iii) 0.25, 0.5, 1.0 or 2.0 micrograms nifedipine kg-1 min-1; or (iv) 5.0 micrograms ritodrine kg-1 min-1. All drug treatments increased the interval between pup deliveries compared with the no surgery and saline controls. Apparent complete tocolysis was observed in 20, 60, 80 and 80% of the animals receiving 0.5, 1.0 or 2.0 micrograms nifedipine kg-1 min-1 or 5.0 micrograms ritodrine kg-1 min-1, respectively. A positive pharmacodynamic relationship was observed for the nifedipine doses. Analysis of pup viability showed no statistically significant difference among treatments. Treatment with 2.0 micrograms nifedipine kg-1 min-1 gave a delay in pup delivery comparable to that with ritodrine.
Tracy
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Department of Pharmacy Practice, School of Pharmacy and Pharmacal Sciences, Purdue University, West Lafayette, IN 47906.
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D000818:Animals; D004305:Dose-Response Relationship, Drug; D005260:Female; D005313:Fetal Death / Q000139:chemically induced; D007743:Labor, Obstetric / Q000187:drug effects*; D009543:Nifedipine / Q000097:blood / Q000494:pharmacology*; D011247:Pregnancy; D011897:Random Allocation; D051381:Rats; D011919:Rats, Inbred Strains; D012312:Ritodrine / Q000494:pharmacology; D015145:Tocolysis / Q000379:methods*
D012312:Ritodrine; D009543:Nifedipine