[CYP3A inhibitors as a pharmacokinetic enhancer: pros and cons of drug interactions].

Certain drugs inherently have unfavourable pharmacokinetic properties; for example, they are poorly absorbed or broken down too quickly in the liver. In some cases, the addition of a pharmacokinetic excipient, thus deliberately causing an interaction, may offer a solution. To date, this concept has been most widely applied in HIV treatment where addition of the CYP3A inhibitors ritonavir and cobicistat greatly increases plasma levels of other HIV medications. For the same reason, ritonavir has been added to the new oral antiviral drug against the SARS CoV-2 virus, nirmatrelvir. In addition to a better and/or longer effect, theoretically lower doses can also be used, resulting in cost savings. Deliberately inducing a pharmacokinetic interaction is not without risk: after all, interactions with other CYP3A substrates can also occur. Nevertheless, we believe that with good interaction management, CYP3A inhibitors can be used safely with benefits for patients and society.