Anastrozole has no progesterone, androgene or estrogen effects. It is an inhibitor of CYPs 1A2, 2C8/C9 and 3A4 in vitro, but hepatic exposure may be insignificant in vivo. Side effects such as nausea, anorexia and vomiting may be potentially porphyrinogenic through reduction in caloric intake.

Anastrozole, a benzyltriazole derivative, is a selective, nonsteroidal aromatase inhibitor.

Anastrozole is used in the treatment of advanced or locally advanced breast cancer, and as adjuvant treatment in hormone receptor-positive early breast cancer. It is administered orally. Common adverse reactions of anastrozole that can be confused with an acute porphyric attack are nausea, vomiting, diarrhoea, and joint pain. Side effects such as nausea, anorexia and vomiting may be potentially porphyrinogenic through reduction in caloric intake.

Average steady state Cmax concentrations in patients in chronic treatment (1 mg/day) are 30-fold lower than the apparent Ki values determined in vitro, and hepatic expose may therefore be insignificant (Grimm, 1997).

Extensively CYP-metabolized in the liver, only 10 per cent excreted as unchanged drug. Maximal plasma concetration in steady state about 100 ng/mL. Anastrozole has been shown to inhibit in vitro metabolic reactions catalyzed by CYP1A2, 2C8/9, and 3A4, but only at relatively high concentrations. Although formal interaction studies have not been performed to date, it is considered unlikely that anastrozole, when administered at the recommended dosage, will result in clinically important interactions with drugs metabolized by CYP enzymes (Grimm, 1997).

Anastrolsole was used uneventfully for 4 months in the treatment of breast cancer in 59 year old PV woman (Thiery-Vuillemin, 2008).

Uneventful use reported in 3 patients with acute porphyria.