Delay of experimentally induced preterm labour in rats with calcium channel blockers and salbutamol.

The effect of some calcium channel blockers on spontaneous activity of uterine strips obtained from 16 day pregnant rats was observed and compared with salbutamol. Nifedipine (2.9, 14 nM), verapamil (2, 10 nM) and diltiazem (11,22nM) both at low and high doses significantly abolished spontaneous contractions which was gradual and persistent. However, salbutamol (4.2, 21 nM) abolished spontaneous activity immediately but the response was shortlived. The effect of these agents was also investigated on experimentally induced preterm labour in rats (ovariectomized on day 16 of pregnancy). In the control group only 21% of foetuses were retained at the end of 48 hr. Nifedipine, verapamil, diltiazem and salbutamol administered ip 8 hourly protected 91%, 90%, 78% and 61% of foetuses from delivery at 48 hr respectively. The rank order of efficacy was nifedipine > verapamil > diltiazem > salbutamol.