Open AccessThe Effect of Labetalol on Contractility of Human Myometrial Preparations
Author(s) -
Thulesius Olav,
Lunell NilsOlov,
Ibrahim Mamoun,
Moberger Birgitta,
Angilivilayil Cherian
Publication year - 1987
Publication title -
acta obstetricia et gynecologica scandinavica
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.401
H-Index - 102
eISSN - 1600-0412
pISSN - 0001-6349
DOI - 10.3109/00016348709020754
Subject(s) - labetalol , myometrium , medicine , phentolamine , contractility , uterine contraction , endocrinology , contraction (grammar) , uterus , epinephrine , verapamil , tocolytic , propranolol , fetus , pregnancy , preterm labor , biology , blood pressure , calcium , genetics
Because of results in animal experiments which demonstrated a partial β 2 ‐adrenoceptor activity of labetalol on rat uterine smooth muscle the present study was conducted in human preparations. The following results were obtained: 1. Rhythmic uterine contractions with a defined steady‐state amplitude and frequency were elicited spontaneously and after methylergometrine. 2. Labetalol reduced amplitude of contractions dose‐de‐pendently after 3 h of incubation. Frequency was unaffected. 3. The tocolytic effect of labetalol is apparent only at high concentrations, above those used in the treatment of hypertension. 4. Neither β 2 ‐specific adrenoceptor blokade with ICI 118,551 nor alpha‐blockade with phentolamine changed amplitude of contraction, either alone or in combination with labetalol. 5. Labetalol has little tocolytic effect on human myometrium in vitro. This effect is unrelated to a‐or β‐antagonism, but seems to depend on a direct smooth muscle depressant effect. In conclusion, from the present in vitro experiments using human myometrial preparations, it seems unlikely that labetalol would interfere with the normal process of labor when used for the treatment of pregnancy hypertension.