Methods and reagents are disclosed for enhancing the bioavailability of a hydrophobic drug, and in some embodiments for determining a hydrophobic drug, in a sample suspected of containing a hydrophobic drug. A combination is formed in a medium where the combination comprises the sample, a hemolytic agent where a determination of the hydrophobic drug is conducted, and a bioavailability agent for the hydrophobic drug. The bioavailability agent comprises an ionic detergent comprising a chain of at least 10 carbon atoms or a non-ionic detergent comprising a chain of at least 15 repeating ethylene oxide units or propylene oxide units or a combination of ethylene oxide units and propylene oxide units. The concentration of the bioavailability agent in the medium is sufficient to enhance the bioavailability of the hydrophobic drug. The medium is incubated under conditions for enhancing the bioavailability of the hydrophobic drug, and in a determination of the hydrophobic drug under conditions for hemolyzing cells in the sample. For determination of the hydrophobic drug, reagents for determining the presence and/or amount of the hydrophobic drug in the sample are added to the medium. The reagents comprise at least one antibody for the hydrophobic drug. The medium is examined for the presence of a complex comprising the hydrophobic drug and the antibody for the hydrophobic drug. The presence and/or amount of the complex indicates the presence and/or amount of the hydrophobic drug in the sample.