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Re: Nifedipine and PTLFrom: Tregoning, S, Shawn, Dr (STREGONG@uctgsh1.uct.ac.za)Thu Mar 28 08:02:50 1996
> Date sent: Tue, 26 Mar 1996 05:15:04 -0600 (CST) > Send reply to: ob-gyn-l@listserv.bcm.tmc.edu > From: "Don Shuwarger, M.D., F.A.C.O.G." <obdoc@inmind.com> > To: stregong@uctgsh1.uct.ac.za > Subject: Nifedipine and PTL
Don Shuwager writes
> There appears to be a common (mis)perception that one of the cardinal concerns with the usage of Nifedipine as a tocolytic agent, is its hypotensive effect. It would appear reasonable to assume that since calcium channel blockers are known to have a vasodilatory and negative inotropic effect, that they would have potentially severe haemodynamic side- effects when administered for tocolytic purposes. This assumtion engenders two concerns with me: 1. There appears to be no published data to substantiate this. Ulmsen et al (1980) reported blood pressure to unaffected by oral administration of nifedipine. In a later study this same author reported a decrease in both systolic and diastolic BP, but these differences did not reach statistical significance. Others, such as Read et al(1986) and Meyer et al (1990) ratified these findings, and although they showed a tendency to lower pressures, these were not statistically significant. The study published by Kupferminc et al in the Br J O&G in 1993 comparing nifedipine with ritodrine, also failed to show a statistically significant reduction in the BP in patients treated with nifedipine. They in fact demonstrated a greater reduction in the group which received ritodrine! For diastolic pressure this difference became significant at 30min (p<0.01), and for mean BP at 45 min (p<0.001) This brings me to my second point, viz 2.Many tend to forget that the betamimetic agents themselves, have been shown to have adverse cardiac effects secondary to their vasodilatory properties. In the same study by Kupferminc et al, ritodrine, in addition to causing a hypotensive response greater than that of nifedipine, also caused a significant tacycardia, which was more pronounced than that of nifedipine. There were also globally more side-effects in the ritodrine group than in the nifedipine group. (23/30 vs 8/30; p<0.001) This has also been the experience of others (Ulmsen 1980, Read 1986, Meyer 1990, Ferguson 1990) Hence it appears from current published data that the side-effect profile of nifedipine is less significant than that of betamimetics. whilst it may be laudable to mention them, we should remain mindful that the "older" agents which we are more familiar with appear,by all accounts, to have a more remarkable negative effect. Shaun Tregoning Registrar: Dept O&G University of Cape Town South Africa
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