inistered with ritonavir, due to induction of CYP1A2.
Anticancer agents
Dasatinib, nilotinib, vincristine, vinblastine
Serum concentrations may be increased when co-administered with ritonavir resulting in the potential for increased incidence of adverse events.
Anticoagulant
Warfarin
S-Warfarin
R-Warfarin
5, single dose
400 q12h
↑ 9%
33%
9%
↔
Induction of CYP1A2 and CYP2C9 lead to decreased levels of R-warfarin while little pharmacokinetic effect is noted on S- warfarin when co-administered with ritonavir. Decreased R-warfarin levels may lead to reduced anticoagulation, therefore it is recommended that anticoagulation parameters are monitored when warfarin is co-administered with ritonavir dosed as an antiretroviral agent or as a pharmacokinetic enhancer.
Anticonvulsants
Carbamazepine
Ritonavir dosed as a pharmacokinetic enhancer or as an antiretroviral agent inhibits CYP3A4 and as a result is expected to increase the plasma concentrations of carbamazepine. Careful monitoring of therapeutic and adverse effects is recommended when carbamazepine is concomitantly administered with ritonavir.
Divalproex, lamotrigine, phenytoin
Ritonavir dosed as a pharmacokinetic enhancer or as an antiretroviral agent induces oxidation by CYP2C9 and glucuronidation and as a result is expected to decrease the plasma concentrations of anticonvulsants. Careful monitoring of serum levels or therapeutic effects is recommended when these medicines are concomitantly administered with ritonavir. Phenytoin may decrease serum levels of ritonavir.
Antidepressants
Amitriptyline, fluoxetine, imipramine, nortriptyline, paroxetine, sertraline
Ritonavir dosed as an antiretroviral agent is likely to inhibit CYP2D6 and as a result is expected to increase concentrations of desipramine, imipramine, amitriptyline, nortriptyline, fluoxetine, paroxetine or sertraline. Careful monitoring of therapeutic and adverse effects is recommended when these medicines are concomitantly administered with antiretroviral doses of ritonavir (see section 4.4)
Desipramine
100, single oral dose
500 q12h
↑ 145%
↑ 22%
The AUC and Cmax of the 2-hydroxy metabolite were decreased 15 and 67%, respectively. Dosage reduction of desipramine is recommended when co-administered with ritonavir dosed as an antiretroviral agent.
Trazodone
50, single dose
200 q12h
↑ 2.4-fold
↑ 34%
An increase in the incidence in trazodone-related adverse reactions was noted when co-administered with ritonavir dosed as an antiretroviral agent or as a pharmacokinetic enhancer. If trazodone is co-administered with ritonavir, the combination should be used with caution, initiating trazodone at the lowest dosage and monitoring for clinical response and tolerability.
Anti-gout treatments
Colchicine
Concentrations of colchicine are expected to increase when co-administered with ritonavir.
Antihistamines
Astemizole, terfenadine
Ritonavir co-administration is likely to result in increased plasma concentrations of astemizole and terfenadine and is therefore contraindicated (see section 4.3).
Fexofenadine
Ritonavir may modify P-glycoprotein mediated fexofenadine efflux w |
