Methylergobrevin is a semi-synthetic derivative of the natural ergot alkaloid (ergometrine), which increases the tone and contractile activity of the myometrium. The stimulating effect of ergot alkaloids on the uterus is manifested in the form of intense contractions. The pregnant uterus, especially at the end of pregnancy, is extremely sensitive to ergot alkaloids. Low doses of methylergometrine cause intense rhythmic contractions of the uterus, which are alternated with periods of relaxation. High doses of this drug cause contractions along with an increase in basal tone. Methylergometrine causes contraction of the smooth muscles of blood vessels. Blood circulation through the spiral arteries is reduced due to the contraction of smooth muscles, and not due to the effect of the drug on the blood vessels of the uterus. This can lead to an increase in central venous pressure, as well as an increase in blood pressure. The effect of methylergometrine on blood pressure is less than that of ergometrine.