title: Pharmacokinetics of sildenafil after intravenous and oral administration in rats: hepatic and intestinal first-pass effects.
abstract: Pharmacokinetics of sildenafil after intravenous and oral administration at various doses and first-pass effect at 30 mg/kg were evaluated in rats. After intravenous administration (10, 30, and 50mg/kg), the dose-normalized AUC values were proportional to intravenous doses studied. However, after oral administration (10, 30, and 100mg/kg), the dose-normalized AUC values increased significantly with increasing doses, possibly due to saturation of metabolism of sildenafil in rat intestinal tract. After oral administration (30 mg/kg), approximately 0.626% was not absorbed and F was 14.6%. The AUC after intragastric administration was significantly smaller (71.4% decrease) than that after intraportal administration, however, the values were not significantly different between intragastric and intraduodenal administration. The above data suggested that intestinal first-pass effect of sildenafil was approximately 71% of oral dose in rats. The AUC values after intraportal administration were significantly smaller (49% decrease) than that after intravenous administration. This suggested that hepatic first-pass effect of sildenafil after absorption into the portal vein was approximately 49% of oral dose in rats (approximately 49% was equivalent to approximately 13.7% of oral dose). The low F of sildenafil at a dose of 30 mg/kg in rats could be mainly due to considerable intestinal first-pass effect.
authors.affiliation: College of Pharmacy and Research Institute of Pharmaceutical Sciences, Seoul National University, San 56-1, Shinlim-Dong, Kwanak-Gu, Seoul 151-742, South Korea.
authors.forename: Hyun S
authors.initials: HS
authors.lastname: Shin
authors.forename: Soo K
authors.initials: SK
authors.lastname: Bae
authors.forename: Myung G
authors.initials: MG
authors.lastname: Lee
mesh_terms: D000284:Administration, Oral; D000818:Animals; D019540:Area Under Curve; D004305:Dose-Response Relationship, Drug; D007262:Infusions, Intravenous; D007413:Intestinal Mucosa / Q000378:metabolism*; D007441:Intubation, Gastrointestinal; D008099:Liver / Q000378:metabolism*; D008297:Male; D010726:Phosphodiesterase Inhibitors / Q000008:administration & dosage / Q000097:blood / Q000493:pharmacokinetics*; D010879:Piperazines / Q000008:administration & dosage / Q000097:blood / Q000493:pharmacokinetics*; D011687:Purines; D051381:Rats; D017207:Rats, Sprague-Dawley; D000068677:Sildenafil Citrate; D013450:Sulfones
chemical_list: D010726:Phosphodiesterase Inhibitors; D010879:Piperazines; D011687:Purines; D013450:Sulfones; D000068677:Sildenafil Citrate