TRANSDERMAL DELIVERY OF KETOROLAC TROMETHAMINE - PERMEATION ENHANCEMENT, DEVICE DESIGN, AND PHARMACOKINETICS IN HEALTHY HUMANS

Transdermal delivery of ketorolac tromethamine, a potent non-narcotic analgesic, through human skin in vitro and in vivo was investigated. I n order to enhance and sustain the flux of ketorolac through human ski n, various compositions of isopropyl alcohol (IPA), water, and isoprop yl myristate (IPM) were evaluated. The solubility of ketorolac acid in an IPA/water binary vehicle mixture increased as the volume fraction of IPA increased from 0 to 90%. The solubility of ketorolac acid in an IPA/water/IPM (saturated) temary vehicle mixture was practically the same as in the IPA/water binary vehicle mixture. The permeation of ket orolac acid through cadaver skin was evaluated using modified Franz di ffusion cells. The skin flux increased as the IPA volume fraction was increased from 0 to 50% and then leveled off beyond 80% IPA loading. W hen IPM was added to the IPA/water binary vehicle mixture, a significa nt increase in the skin flux of ketorolac was observed. The skin flux decreased exponentially as the donor solution pH was raised from 3.5 t o 7.0. The permeability of ketorolac through various membranes such as a microporous membrane and pressure-sensitive adhesive was evaluated. While a microporous membrane offered practically no diffusion resista nce, the in vitro flux of ketorolac through cadaver skin decreased sub stantially upon lamination of pressure-sensitive adhesive onto a micro porous membrane. Three liquid-reservoir type transdermal devices were fabricated using 6.5% ketorolac tromethamine gel, a microporous membra ne, an adhesive membrane, and polyester backing film: TD-A (microporou s membrane/acrylic adhesive), TD-B (microporous membrane/silicone adhe sive), and TD-C (microporous membrane). The pharmacokinetics of ketoro lac in 10 healthy humans following application of a transdermal device for 24 h was evaluated, The maximum plasma concentrations (C-max) wer e 0.20, 0.18, and 0.82 mu g/mL for TD-A, TD-B, and TD-C, respectively. The total AUC values for the concentration-time curves were TD-C > TD -A > TD-B, and the terminal half-life ranged from 6.6 to 9.7 h.