Table 11. Drug interactions between protease inhibitors and other drugs; drug interactions requiring dose modifications

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Drug Interactions Requiring Dose Modifications

	Indinavir	Ritonavir	Saquinavir*	Nelfinavir
Fluconazole	No dose change	No dose change	No data	No dose change
Ketoconazole and Itraconazole	Decrease dose to 600 mg q8h	Increases ketoconazole >3 fold; dose adjustment required	Increases saquinavir levels 3-fold; no dose change	No dose change
Rifabutin	Reduce rifabutin to half dose: 150 mg qd	Consider Alternative drug or reduce rifabutin dose to one quarter	Not Recommended with either Invirase or Fortovase	Reduce rifabutin to half dose: 150 mg qd
Rifampin	Contraindicated	Unknown***	Not recommended with either Invirase or Fortovase	Contraindicated
Oral Contraceptives	Modest increase Ortho-Novum levels; no dose change	Ethinyl estradiol levels decreased; use alternative or additional contraceptive method	No data	Ethinyl estradiol and norethindrone levels decreased; use alternative or additional contraceptive method
Miscellaneous	Grapefruit juice reduces indinavir levels by 26%	-Desipramine increased 145%: reduce dose -Theophylline levels decreased: dose increase	Grapefruit juice increases saquinavir levels**

 

* Several drug interaction studies have been completed with saquinavir given as INVIRASE or FORTOVASE. Results from studies conducted with INVIRASE may not be applicable to FORTOVASE.

** Conducted with INVIRASE

*** Rifampin reduces ritonavir 35%. Increases ritonavir dose or use of ritonavir in combination therapy is strongly recommended. The effect of ritonavir on rifampin is unknown. Used concurrently, there may be increased liver toxicity. Therefore, patients on ritonavir and rifampin should be monitored closely.