Low extent of oxidative metabolism. Inducer of CYP 3A4. Three references consider it safe. Occasional patient reports of suspected porphyrinogenicity, but vast and significant clinical experience of non-porphyrinogenicity.

(To be edited, initial data ST OCT 04) Anilide (acetaminophen) derivative metabolized by conjugation with glucuronic acid and sulfate. A small part (<4%) is oxidatively metabolized by CYPs and excreted as cysteine and mercapto conjugates. At low concentrations inducer of CYP 3A4, increasing activity and content. Australian list: safe. South African list: use French list: avoid, known to have precipitated an acute attack Thunell; patient inquiry: tolerated (n=28), possibly not tolerated (n=2 C. Andersson; patient inquiry: used without illeffecs (n=18). Used in Swedish porphyria ward . See e.g. Feierman et al. The paradoxical effect of acetaminophe on CYP3A4 activity and content in transfected HepG2 cells. Arch Biochem Biophys 2002 398: 109-17.

Uneventful use reported in 430 patients with acute porphyria.