K. N. M., A. R. Effect of intramuscular tramadol hydrochloride as a labor analgesic in primagravidae. International Journal of Reproduction, Contraception, Obstetrics and Gynecology, [S. l.], v. 5, n. 3, p. 615–619, 2017. DOI: 10.18203/2320-1770.ijrcog20160460. Disponível em: https://www.ijrcog.org/index.php/ijrcog/article/view/687. Acesso em: 13 oct. 2025.