Interferon alfa natural is a mixture of cytokines and fever and flu-like symptoms are very common adverse reactions. Experience seems to be that infection may trigger attacks of acute porphyria. However, infections are not commonly reported in the treatment with interferon alfa natural, and there is no evidence to show that inflammation and fever alone are triggering factors. Chronic inflammatory diseases are not associated with higher incidence of porphyric attacks. Inflammation has also shown to down-regulate the activity and expression of cytochrome P450 enzymes involved in hepatic drug clearance. Through inhibition of ALAS1-induction, interferon alfa natural might therefore protect against attacks of acute porphyria. However, very common side effects such as nausea and vomiting are potentially porphyrogenic through reduction in caloric intake.

Interferon alfa natural is a mixture of naturally occurring human interferon alfa proteins recovered from supernate of primary human leukocyte cultures incubated with Sendai virus.

Interferon alfa natural is used as adjuvant therapy of high-risk patients with cutaneous melanoma and in the treatment of patients that have initially responded to recombinant interferon alpha, but who have become resistent. It is administered subcutaneously. Common adverse reactions of interferon alfa natural are influenza-like symptoms like fever, fatigue, musculoskeletal pain, diarrhea and nausea. Several of these effects can be confused with an acute porphyric attack. Side effects such as anorexia, nausea and diarrhea may be potentially porphyrinogenic through reduction in caloric intake.

Interferon alfa natural is mainly eliminated by the kidneys. Inflammation suppresses the expression of several hepatic transporters and detoxifying CYPs including CYP3A4 (Aitken, 2005; Moreau, 2008).