Intratracheal administration of fentanyl: pharmacokinetics and local tissue effects

Methylene blue in preventing hemodynamic and metabolic derangement following superior mesenteric artery clamping/unclamping: an intratracheal vs. intraperitoneal dose-response study

Intestinal ischemia-reperfusion affects hemodynamics. We studied intratracheal vs. intraperitoneal methylene blue (MB) attenuation of hemodynamic and metabolic deterioration following superior mesenteric artery (SMA) clamping/unclamping. Murine SMAs (5/group) were clamped for 1 h. MB (2, 6, 20, or 60 mg/kg [MB-2, MB-6, MB-20, and MB-60]) was administered intraperitoneally or intratracheally 10 min before unclamping. Observation continued for another 3 h. Circulating xanthine oxidase and base deficit levels doubled among ischemia non-treated and ischemia MB-2- and MB-60-treated groups, blood pressure decreased by 50%, and heart rate increased by 35%, compared to controls (non-clamped/unclamped and non-MB-treated rats, P < 0.01). These three ischemia groups needed 3-fold the amount of fluid to maintain systolic pressure > or =60 mmHg than controls (P < 0.01). Only the MB-6 and MB-20 intraperitoneal and intratracheal regimens similarly afforded hemodynamic stability in ischemic animals; base deficit and resuscitation volumes normalized as well. No drug regimen affected heart rate. We concluded that intraperitoneal and intratracheal MB at specific doses prevented systemic derangement following SMA clamping/unclamping.

Evaluation of poly(ethylene oxide)-poly(propylene oxide)-poly(ethylene oxide) (PEO-PPO-PEO) gels as a release vehicle for percutaneous fentanyl

The primary objective of this study was to investigate the feasibility of PEO-PPO-PEO copolymer gel as a release vehicle for percutaneous administration of fentanyl in vitro and in vivo. A cellulose membrane and nude mouse skin with series concentrations of PEO-PPO-PEO block copolymers were used to examine the sustained-release pattern and permeation of fentanyl. The in vivo percutaneous absorption was examined using rabbits to evaluate the preliminary pharmacokinetics of fentanyl with 46% PEO-PPO-PEO copolymer formulation patches. The micelle formation ability of this block copolymer and the penetration ability of PEO-PPO-PEO copolymer over time were also studied by pyrene fluorescence probe methods and the dynamic light scattering test. At a concentration of 46% at 37 degrees C, PEO-PPO-PEO copolymers formed a gel and showed a pseudo-zero-order sustained-release profile. With increasing concentration of copolymer in the cellulose membrane transport, the apparent release flux of fentanyl (200 microgram/ml) decreased to 1. 09+/-0.19 microgram cm(-2) h(-1). Assessment of the effect of the copolymer on nude mouse skin also showed a decrease in the apparent permeability coefficient [(P(H(2)O))=2.24+/-0.47x10(-6) cm s(-1) vs. (P(46% block copolymer))=0.93+/-0.23x10(-7) cm s(-1)]. The preliminary pharmacokinetics of the fentanyl patch was shown to be in steady state within 24 h, and this was maintained for at least 72 h with an elimination half-life (t(1/2)) of 10.5+/-3.4 h. A fluorescence experiment showed polymeric micelle formation of PEO-PPO-PEO copolymers at 0.1% (w/w) within 50 nm micelle size and the PEO-PPO-PEO copolymers were able to penetrate nude mouse skin within 24 h. Thus, it appears that fentanyl preparations based on PEO-PPO-PEO copolymer gel might be practical for percutaneous delivery.