Anabolic steroids are synthetic substances related to male sex hormones (androgens). Although it is illegal in the United States to possess or distribute anabolic steroids for nonmedical use, a "black market" for them exists, and many amateur and professional athletes take them to enhance performance. In many cases, the athletes take doses that are extremely high—perhaps 100 times the doses that might be prescribed for medical use. As a result, they put themselves in real danger of short-term and long-term health problems. Blood testing, as has been used in the Olympic Games, can detect, identify, and quantify the presence of anabolic steroids in the blood of athletes, which can lead to the disqualification of an athlete.
The effect of solubilization by micelles on the transport of steroids across microporous membranes has been studied theoretically and experimentally. Our theoretical model requires the following parameters: micelle and drug diffusion coefficients in free solution, the distribution coefficient of the drug between the bulk and micellar phases, and micelle and membrane pore radil. The steroids used were hydrocortisone, testosterone, and progesterone. Since the model accounts for the flux of free drug as well as micelle-solubilized drug, the distribution coefficient of the drug between micelles and the aqueous phase had to be determined by solubilization experiments for each of the steroids. Membrane pore diameters, as determined by scanning electron microscopy (SEM) and transmission electron microscopy (TEM), ranged from ˜500 to 4000 A. Steroid diffusion coefficients were calculated from membrane diffusion experiments. Quasi-elastic light scattering was used to find the free-solution diffusion coefficients and hydrodynamic radii of the micelles. With these experimentally determined parameters, the model is shown to be capable of predicting the rate of transport of micelle-solubilized drugs through microporous membranes. The application of our model to the design of controlled-release devices is also discussed.