CYP3A4 is involved in about 50% of drug metabolism, so there is a high risk of drug-to-drug interactions with this enzyme. Ritonavir (trade name Norvir - Abbott Laboratories) is an antiretroviral drug from the protease inhibitor class used to treat HIV infection and AIDS and is a potent inhibitor of CYP3A4.
Substrates of CYP2D6 include tricyclic antidepressants, antipsychotics (eg, haloperidol), MDMA, SSRIs, beta blockers, and opiates. Drug-to-drug interactions can occur with all of these drugs when taken in combination with CYP2D6 inhibitors.
