Special instructions Ritonavir should be taken with food if possible. Some drugs taken together may have interactions that cause illness or make the drugs less effective. Always check with a doctor or pharmacist before taking any other medicine to be sure it will not interact with ritonavir. Birth control pills or other hormonal contraceptives may be less effective when given with ritonavir. A different form or backup method of birth control should be used by women taking ritonavir.
Tobacco reduces the amount of ritonavir in the body.
Rifabutin should not be taken with ritonavir, because it reduces the amount of ritonavir in the body. Clarithromycin dosage may need to be adjusted in people who also have kidney disease. Because ritonavir increases the amount of some other drugs in the body, they may cause much more intense side effects, such as irregular heartbeat, blood disorders, or seizures. Extreme sedation and severe breathing problems may result from taking some medications in combination with ritonavir. Because ritonavir increases the amount of some other drugs in the body, they may cause much more intense side effects.