Norethisterone Ritonavir

Amprenavir and atazanavir, given alone increase the levels of ethinylestradiol and norethisterone. Ritonavir and nelfinavir, in contrast to the effect that would normally be expected decrease the levels of ethinylestradiol. Reduced ethinylestradiol and norethisterone levels occur with fosamprenavir, lopinavir and ti-pranavir given with ritonavir. Indinavir does not appear to interact. 

PROTEASE INHIBITORS PROGESTOGENS -NORETHISTERONE t adverse effects with amprenavir and atazanavir. Possibly 1 efficacy and risk of contraceptive failure with nelfinavir and ritonavir (with or without lopinavir) Uncertain Advise patients to use additional contraception for the period of intake and for 1 month after stopping coadministration with these drugs. Barrier methods are necessary to prevent transmission of infection from patients with HIV. Watch for early features of toxicity of amprenavir and atazanavir, and adjust the dose accordingly... 

Tipranavir given with low-dose ritonavir decreased the AUC and maximum concentration of ethinyiestradiol by 50%, but did not significantly alter the pharmacokinetics of norethisterone. ... 

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