Viagra Research Today is a free monthly online journal that collates and summarizes the latest research about Viagra, including details on sildenafil, erectile dysfunction, impotence, side-effects, alternatives.

In vivo dilation of fetal and neonatal ductus arteriosus by inhibition of phosphodiesterase-5 in rats.

Momma K, Toyoshima K, Imamura S, Nakanishi T

Department of Pediatric Cardiology, Tokyo Women's Medical University, Kawada-cho, Shinjuku-ku, Tokyo 162-8666, Japan. prmomma@hij.twmu.ac.jp

A recent in vitro study showed that sildenafil, a type 5 phosphodiesterase inhibitor, dilated the constricted ductus arteriosus of neonatal rabbits. We studied the in vivo ductus-dilating effects of sildenafil in fetal and neonatal rats. Ductus diameters were measured with whole-body freezing and cutting on a freezing microtome. Indomethacin (10 mg/kg) constricted the fetal ductus severely at 4 and 8 h after orogastric administration to the dams. Sildenafil, administered orogastrically and simultaneously with indomethacin, dilated the near-term fetal [21 fetal days (FD)] ductus constricted by indomethacin completely with 1 mg/kg at 8 h after administration. The preterm fetal ductus was more sensitive to sildenafil at 19FD. The ductus constricted rapidly after birth, and the ductal diameter was only 10% of the fetal diameter at 1 h after birth. The ductus-dilating effect of sildenafil was studied by i.p. injection at 1 h after birth, and the ductus diameter was studied 30 and 60 min later. Sildenafil dilated the neonatal constricted ductus moderately with a massive dose (100 mg/kg) and only minimally with 1 mg/kg. In conclusion, sildenafil, a type 5 phosphodiesterase inhibitor, dilated the constricted fetal ductus completely at 8 h with 1 mg/kg in the near-term fetus and completely with a smaller dose (0.1 mg/kg) in the preterm fetus. However, sildenafil dilated the neonatal constricted ductus only moderately with large doses and minimally with 1 mg/kg. Probably, sildenafil is useful clinically for treating idiopathic and secondary fetal ductal constriction and not useful for dilation of the neonatal constricted ductus.

Published 29 June 2005 in Pediatr Res, 58(1): 42-5.
Full-text of this article is available online (may require subscription).

© 2004-2008 Viagra Research Today. All Rights Reserved.