Ketoconazole / Itraconazole: co-administration of fosamprenavir 700 mg with ritonavir 100 mg twice daily and ketoconazole 200 mg once daily increased plasma ketoconazole Cmax by 25% and increased AUC(0-τ) to values 2.69-fold those observed on administration of ketoconazole 200 mg once daily without concurrent fosamprenavir with ritonavir.