CYP enzymes bind medications (ie: substrates). Recalling regular biochemistry, the reaction can proceed and the enzyme releases the product (usually an inactivated metabolite). The likelihood for the reaction to go to completion is described by a coefficient Km. Sometimes an enzyme has such a high affinity for a substrate that it binds strongly to the substrate and is reluctant to let it go. This is described by the coefficient Ki (the lower the coefficient, the more likely it is to inhibit the enzyme). Enzymes with a low Ki for a substrate are considered inhibitors. Sometimes the enzyme releases the substrate without completing the reaction (K-1). Some substrates will bind an enzyme more strongly than other substrates. This is termed competitive inhibition. Finally, some medications induce new transcription of new enzymes. This process typically takes a few days