vir is used as a pharmacokinetic enhancer is also contained in the Summary of Product Characteristics of the co-administered protease inhibitor.
Medicinal products that affect ritonavir levels
Serum levels of ritonavir can be reduced by concomitant use of herbal preparations containing St John's wort (Hypericum perforatum). This is due to the induction of medicinal product metabolising enzymes by St John's wort. Herbal preparations containing St John's wort must not be used in combination with ritonavir. If a patient is already taking St John's wort, stop St John's wort and if possible check viral levels. Ritonavir levels may increase on stopping St John's wort. The dose of ritonavir may need adjusting. The inducing effect may persist for at least 2 weeks after cessation of treatment with St John's wort (see section 4.3).
Serum levels of ritonavir may be affected by select co-administered medicinal products (eg delavirdine, efavirenz, phenytoin and rifampicin). These interactions are noted in the medicinal product interaction tables below.
Medicinal products that are affected by the use of ritonavir
Interactions between ritonavir and protease inhibitors, antiretroviral agents other than protease inhibitors and other non-antiretroviral medicinal products are listed in the tables below.
Medicinal Product Interactions – Ritonavir with Protease Inhibitors
Co-administered Medicinal Product
Dose of Co-administered Medicinal Product (mg)
Dose of NORVIR (mg)
Medicinal Product Assessed
AUC
Cmin
Amprenavir
600 q12h
100 q12h
Amprenavir2
↑ 64%
↑ 5 fold
Ritonavir increases the serum levels of amprenavir as a result of CYP3A4 inhibition. Clinical trials confirmed the safety and efficacy of 600 mg amprenavir twice daily with ritonavir 100 mg twice daily. Norvir oral solution should not be co-administered with amprenavir oral solution to children due to the risk of toxicity from excipients in the two formulations. For further information, physicians should refer to the Agenerase Summary of Product Characteristics.
Atazanavir
300 q24h
100 q24h
Atazanavir
↑ 86%
↑ 11 fold
Atazanavir1
↑ 2 fold
↑ 3-7 fold
Ritonavir increases the serum levels of atazanavir as a result of CYP3A4 inhibition. Clinical trials confirmed the safety and efficacy of 300 mg atazanavir once daily with ritonavir 100 mg once daily in treatment experienced patients. For further information, physicians should refer to the Reyataz Summary of Product Characteristics.
Darunavir
600, single
100 q12h
Darunavir
↑ 14 fold
Ritonavir increases the serum levels of darunavir as a result of CYP3A inhibition. Darunavir must be given with ritonavir to ensure its therapeutic effect. Ritonavir doses higher than 100 mg twice daily have not been studied with darunavir. For further information, refer to the Summary of Product Characteristics for Prezista.
Fosamprenavir
700 q12h
100 q12h
Amprenavir
↑ 2.4 fold
↑ 11 fold
Ritonavir increases the serum levels of amprenavir (from fosamprenavir) as a result of CYP3A4 inhibition. Fosamprenavir must be given with rito |
