NCIt definition : The hydrochloride salt form of ritodrine, a phenethylamine derivative with tocolytic
activity. Ritodrine hydrochloride binds to and activates beta-2 adrenergic receptors
of myocytes in the uterine myometrium, which results in decreased intensity and frequency
of uterine contraction. Specifically, ritodrine hydrochloride probably activates adenyl
cyclase, thereby increasing production of cyclic adenosine monophosphate (cAMP), which
in turn enhancing the efflux of calcium from vascular smooth muscle cells. A lack
of intracellular calcium prevents uterine myometrial contraction. In addition, this
agent may directly inactivate myosin light chain kinase, a critical enzyme necessary
for the initiation of muscle contractions.;