In vitro uterine response to tetramethylpyrazine, the active constituent of chung chong (a traditional Chinese medicine).

Tetramethylpyrazine is extracted from Rhizoma ligustici wallichii, an herb used in the Chinese medicine Chung Chong. Both herb and extract have been used in the treatment of anginal pain and stroke. Animal studies in the West have shown that tetramethylpyrazine improves coronary blood flow, is short acting, and has a low toxicity. There are no clinical or animal studies on the uterine effects of tetramethylpyrazine. We present results of a preliminary study with isolated uterine strips from rats. We found that tetramethylpyrazine, in a dose-dependent manner (0.6 to 20 micrograms/ml), reduced uterine diastolic tone and inhibited the response to oxytocin (0.02 to 0.32 micrograms/ml). Higher concentrations of tetramethylpyrazine were needed to block the uterine responses to prostaglandin E2 (0.01 to 0.1 microgram/ml). On the basis of clinical and folk experience in the Far East, tetramethylpyrazine appears to have fewer systemic effects in human beings than have the beta-adrenergic agonists or calcium channel blockers. We suggest that studies in the whole animal and in the clinic might provide reasons to use tetramethylpyrazine to reduce uterine contractions and tone in pregnant women at term.