Drug interactions may change how your medications work or increase your risk for serious side effects. This document does not contain all possible drug interactions. Keep a list of all the products you use (including prescription/nonprescription drugs and herbal products) and share it with your doctor and pharmacist. Do not start, stop, or change the dosage of any medicines without your doctor's approval.

Ritonavir interacts with many medications. Some products that may interact with this drug include: cobicistat, disulfiram, orlistat.

Ritonavir can slow down or speed up the removal of other medications from your body, which may affect how they work. Examples of affected drugs include alfuzosin, antiarrhythmics (such as amiodarone, flecainide, propafenone, quinidine), azole antifungals (such as voriconazole), certain benzodiazepines (midazolam, triazolam), certain "blood thinners" (such as rivaroxaban, warfarin), eletriptan, drugs to treat erectile dysfunction-ED or pulmonary hypertension (such as avanafil, sildenafil), ergot alkaloids (such as dihydroergotamine, ergonovine, ergotamine, methylergonovine), lurasidone, certain opioid pain medications (such as fentanyl, meperidine), pimozide, ranolazine, salmeterol, "statin" cholesterol drugs (such as simvastatin, lovastatin), among others.

Other medications can affect the removal of ritonavir from your body, which may affect how ritonavir works. Examples include apalutamide, rifampin, St. John's wort, among others.

This medication may decrease the effectiveness of hormonal birth control such as pills, patch, or ring. This could cause pregnancy. Discuss with your doctor or pharmacist if you should use reliable backup birth control methods while using this medication. Also tell your doctor if you have any new spotting or breakthrough bleeding, because these may be signs that your birth control is not working well.