Norethisterone Nelfinavir

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... 

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. 

The manufacturer briefly notes that in women taking a combined oral contraceptive (ethinylestradiol/norethisterone 35/400 micrograms) nelfinavir 750 mg three times daily for one week decreased the AUCs of ethi-nylestradiol and norethisterone by 47% and 18%, respectively. In a retrospective study 7 of 21 women taking nelfinavir experienced contraceptive failure (overall there were 8 contraceptive failures out of 33 women taking protease inhibitors). However, medication adherence could not be confirmed. ... 

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