In vivo in vitro correlations for a poorly soluble drug, danazol, using the flow-through dissolution method with biorelevant dissolution media

The purpose of the study was to design dissolution tests that were able to distinguish between the behaviour of danazol under fasted and fed conditions, by using biorelevant media. In vitro dissolution of 100 mg danazol capsules was performed using the flow-through dissolution method. Flow rates were 8, 16 or 32 ml/min, corresponding to total volumes dissolution medium of 960, 1920 and 3840 ml, respectively. The media used contained bile salt and phospholipid levels relevant for either fasted or fed conditions in vivo. Crude and inexpensive bile components, Porcine Bile Extract and soybean phospholipids, were used as the bile source. The effect of adding different concentrations and molar ratios of monoglycerides and fatty acids to the fed state media was investigated. In vivo release profiles under fasted and fed conditions were obtained from a previous study by deconvolution [Sunesen, V.H., Vedelsdal, R., Kristensen, H.G., Christrup, L., Müllertz, A. 2005. Effect of liquid volume and food intake on the absolute bioavailability of danazol, a poorly soluble drug, Eur. J. Pharm. Sci. 24, 297-303]. In the fasted state, the physiologically most relevant correlation with in vivo results was achieved with a medium containing 6.3 mM bile salts and 1.25 mM phospholipids (8 ml/min). A medium containing 18.8 mM bile salts, 3.75 mM phospholipids, 4.0 mM monoglycerides and 30 mM fatty acids (8 ml/min) gave the closest correlation with fed state in vivo results. By using the flow-through dissolution method it was possible to obtain correlations with in vivo release of danazol under fasted and fed conditions. Both hydrodynamics and medium composition were important for the dissolution of danazol. In the fed state an IVIVC could only be obtained by including monoglycerides and fatty acids in the medium.