<qa>  What is a non-inducible isoform?We propose to use these validated and widely accepted methods to evaluate the drug-interaction potential of a characterized MT supplement. A clinical protocol, using 16 normal volunteers, will evaluate the potential to inhibit or induce CYP3A4, CYP1A2, CYP2C9, and the potential to inhibit CYP2D6 a non-inducible isoform. Test doses of these four safe probe drugs will be administered at baseline before treatment with MT and after a 14-day treatment period. Changes in the pharmacokinetics of these probe drugs will indicate the degree of specific enzyme inhibition or induction, respectively. These data will be used to evaluate the effects of combining a standardized MT supplement with other drugs that are substrates for the CYP enzymes studied. 