Pharmacokinetic enhancers (boosters) are compounds used in combination with a primary therapeutic agent (drug) and are not used for their direct effects on the disease but because they enhance or restore the activity of the primary agent. Hence, in certain cases, they represent an indispensable escort for
enzyme-labile drugs. Pharmacokinetic enhancers can exert their activity on different ways. In the most common case, they inhibit
enzymes such as human
cytochrome P450 enzymes in the liver or other organs and, thereby, block or reduce undesired metabolism and inactivation of the primary drug. In this review, an overview will be given on the therapeutically most important classes of pharmacokinetic enhancers like β-lactamase inhibitors, inhibitors of CYP (
cytochrome P450)
enzymes in HIV
therapy and
hepatitis C, boosters for fluoropyrimidine-type
anticancer agents, compounds utilized for enabling
therapy of
Parkinson's disease with
levodopa, and others. Inhibitors of efflux pumps in both pathogenic bacteria and
tumor cells will be addresses shortly.