"The cystic fibrosis (CF) drug Orkambi (Vertex Pharmaceuticals) has received a green light from the European Medicines Agency (EMA) Committee for Medicinal Products for Human Use (CHMP).
Orkambi is a fixed-dose oral combination "...
Heme acts to limit the hepatic and/or marrow synthesis of porphyrin. This action is likely due to the inhibition of δ-aminolevulinic acid synthetase, the enzyme which limits the rate of the porphyrin/heme biosynthetic pathway. The exact mechanism by which hematin produces symptomatic improvement in patients with acute episodes of the hepatic porphyrias has not been elucidated.1,9
Following intravenous administration of hematin in non-jaundiced human patients, an increase in fecal urobilinogen can be observed which is roughly proportional to the amount of hematin administered. This suggests an enterohepatic pathway as at least one route of elimination. Bilirubin metabolites are also excreted in the urine following hematin injections.2
PANHEMATIN (hemin for injection) therapy for the acute porphyrias is not curative. After discontinuation of PANHEMATIN treatment, symptoms generally return although in some cases remission is prolonged. Some neurological symptoms have improved weeks to months after therapy although little or no response was noted at the time of treatment.
Other aspects of human pharmacokinetics have not been defined.
1. Bickers, D., Treatment of the Porphyrias: Mechanisms of Action, J Invest Dermatol 77(1):107-113, 1981.
2. Watson, C. J., Hematin and Porphyria, editorial, N Engl J Med 293(12):605- 607, September 18, 1975.
9. Pierach, C. A., Hematin Therapy for the Porphyric Attack, Semin Liver Dis 2(2):125-131, May, 1982.
Last reviewed on RxList: 9/18/2013
This monograph has been modified to include the generic and brand name in many instances.
Additional Panhematin Information
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