The comparative actions of uterine inhibiting drugs.
Currently there is not an in vitro or in vivo method of quantitating the potency of uterine inhibiting drugs. Electric field stimulation (EFS) of pregnant and parturient rabbit myometrial strips has been effectively used to assay oxytocic potency of prostaglandins and it is shown in this study to be useful in assaying potency of beta-sympathomimetic compounds. Decreasing electric field stimulation (DEFS) provides three measureable endpoints: tension, excitability, and threshold voltage. Three compounds were tested for these parameters: isoproterenol, ritodrine, and isoxsuprine. It is also revealed that so-called uterine inhibition by these compounds represents the creation of a chaotic fibrillating muscle which is unable to respond in a synchronous way to produce a contraction of maximal tension.
D000818:Animals; D003864:Depression, Chemical; D004558:Electric Stimulation; D005260:Female; D006801:Humans; D007545:Isoproterenol / Q000494:pharmacology*; D007556:Isoxsuprine / Q000494:pharmacology*; D009215:Myometrium / Q000187:drug effects; D009638:Norepinephrine / Q000494:pharmacology; D011247:Pregnancy; D011412:Propanolamines / Q000494:pharmacology*; D011433:Propranolol / Q000494:pharmacology; D011817:Rabbits; D012312:Ritodrine / Q000494:pharmacology*; D014590:Uterine Contraction / Q000187:drug effects*
D011412:Propanolamines; D011433:Propranolol; D012312:Ritodrine; D007545:Isoproterenol; D007556:Isoxsuprine; D009638:Norepinephrine