• Archives of Pharmacal Research
• /
• v.20 no.1
• /
• pp.24-28
• /
• 1997

In the present study, a pharmacokinetic model to address the effects of the diffusional barrier between splanchnic bed and enterocytes on the extent of presystemic and systemic intestinal elimination of drugs was developed. The model is composed of five compartments, ie., gut lumen, enterocyte, splanchnic bed, liver and central compartments. The equations for various pharmacokinetic parameters important for estimating the quantitative differences between presystemic and systemic intestinal and hepatic elimination of drugs were derived. A simulation study demonstrated that the diffusions[ barrier present between splanchnic blood and enterocytes can have significant effects on oral bioavailability and systemic clearance of drugs. In conclusion, the model can be useful for a better understanding of the effects of diffusional barrier on the extent of administration-route dependent intestinal and hepatic elimination of drugs, especially those with high hydrophilicity and/or charge(s) under physiological conditions.

• Journal of Pharmaceutical Investigation
• /
• v.27 no.1
• /
• pp.15-22
• /
• 1997

The mucosal route of administration(nasal, buccal, conjunctival and vaginal) has recently been considered as an alternative to parenteral delivery for many peptide drugs because enzymatic degradation of these agents may be partly avoided. The objective of these study was to establish the optimal mucosal administration dosage form of $LHRH/[D-Ala^6]LHRH$, based on presystemic metabolism. We reported previously the peptidase inhibition effect of medium chain fatty acid salts(sodium caprylate, soadium caprate and sodium laurate), EDTA and STDHF on the proteolysis of $LHRH/[D-Ala^6]LHRH$ in rabbit mucosal homgenates. We also reported that EDTA, STDHF and sodium laurate markedly increased the potency of $LHRH/[D-Ala^6]LHRH$ solution applied vaginally. In the present study, by administration of polycarbophil hydrogel containing LHRH the ovulation inducing activity was 3.3 times greater than solution. These results indicate not only peptidase inhibitor but also polycarbophil hydrogel significantly improved the absorption of this drug. The results of this study would provide the feasibility as a rational dosage form for improving bioavailability and self administration of this hydrogel by the vaginal application.