To assess plasma steady-state pharmacokinetics ( PK ) of rifampicin , isoniazid , saquinavir and ritonavir in HIV and tuberculosis ( TB ) co-infected patients , and investigate potential interactions between TB drugs and protease inhibitors ( PIs ) .
Pharmacokinetic interaction between rifampicin and the once-daily combination of saquinavir and low-dose ritonavir in HIV-infected patients with tuberculosis.  To assess plasma steady-state pharmacokinetics ( PK ) of rifampicin , isoniazid , saquinavir and ritonavir in HIV and tuberculosis ( TB ) co-infected patients , and investigate potential interactions between TB drugs and protease inhibitors ( PIs ) . ### methods Open-label, single-arm, sequential PK study including 22 patients with HIV infection and TB. During the first 2 months, patients received rifampicin, isoniazid and pyrazinamide, with or without ethambutol (first PK study, n = 22). Then patients stopped pyrazinamide and ethambutol and started once-daily antiretroviral therapy (ART) with didanosine, lamivudine, ritonavir (200 mg) and saquinavir (1600 mg) (second PK study, n = 18). Patients stopped all TB drugs after 9 months continuing the same ART (third PK study, n = 15). Differences between TB drug parameters in the first and second PK studies, and between PI parameters in the second and third PK studies were used to assess interactions. ### results Rifampicin and isoniazid pharmacokinetics did not change substantially with saquinavir and ritonavir. A significant 39.5%, 34.9% and 48.7% reduction in median saquinavir AUC(0-24), C(max) and C(trough), respectively, was seen with rifampicin and isoniazid. ritonavir AUC(0-24), C(max) and C(trough) decreased 42.5%, 49.6% and 64.3%, respectively, with rifampicin and isoniazid. ### conclusions There was a significant interaction between saquinavir, ritonavir and rifampicin, with reduction in median plasma concentrations of saquinavir and ritonavir. saquinavir should be given with caution in patients receiving rifampicin. Twice-daily dosing or higher saquinavir doses in once-daily administration should be tested to obtain more appropriate plasma levels.
### Instruction:
            Given the context about compound efficacy for the given treatment mentioned within the input, mentioned the compounds 
            that can co-occur for the mentioned treatment

            ### Input:
            Pharmacokinetic interaction between rifampicin and the once-daily combination of saquinavir and low-dose ritonavir in HIV-infected patients with tuberculosis.  To assess plasma steady-state pharmacokinetics ( PK ) of rifampicin , isoniazid , saquinavir and ritonavir in HIV and tuberculosis ( TB ) co-infected patients , and investigate potential interactions between TB drugs and protease inhibitors ( PIs ) . ### methods Open-label, single-arm, sequential PK study including 22 patients with HIV infection and TB. During the first 2 months, patients received rifampicin, isoniazid and pyrazinamide, with or without ethambutol (first PK study, n = 22). Then patients stopped pyrazinamide and ethambutol and started once-daily antiretroviral therapy (ART) with didanosine, lamivudine, ritonavir (200 mg) and saquinavir (1600 mg) (second PK study, n = 18). Patients stopped all TB drugs after 9 months continuing the same ART (third PK study, n = 15). Differences between TB drug parameters in the first and second PK studies, and between PI parameters in the second and third PK studies were used to assess interactions. ### results Rifampicin and isoniazid pharmacokinetics did not change substantially with saquinavir and ritonavir. A significant 39.5%, 34.9% and 48.7% reduction in median saquinavir AUC(0-24), C(max) and C(trough), respectively, was seen with rifampicin and isoniazid. ritonavir AUC(0-24), C(max) and C(trough) decreased 42.5%, 49.6% and 64.3%, respectively, with rifampicin and isoniazid. ### conclusions There was a significant interaction between saquinavir, ritonavir and rifampicin, with reduction in median plasma concentrations of saquinavir and ritonavir. saquinavir should be given with caution in patients receiving rifampicin. Twice-daily dosing or higher saquinavir doses in once-daily administration should be tested to obtain more appropriate plasma levels.

            ### Response:
            isoniazid, saquinavir, ritonavir, rifampicin
            