Hemin Other names: Haem

Haem arginate is indicated for hepatic porphyria (intermittent acute porphyria, porphyria variegata and hereditary coproporphyria). These porphyrias are characterised by the existence of an enzymatic block in the pathway of haem biosynthesis resulting in:

1. a deficit of haem necessary for the synthesis of various haemoproteins.
2. mainly the accumulation ahead of the metabolic block of haem precursors which are directly or indirectly toxic to the organism.

The administration of hemin, by reducing the haem deficit, suppresses by feedback the activity of delta-amino-laevulinic synthase (the key enzyme in the synthesis of the porphyrins) which reduces the production of porphyrins and of the toxic precursors of haem. Therefore, by contributing to the re-establishment of normal levels of haemoproteins and of respiratory pigments, haem corrects the biological disorders observed in patients with porphyria. As the bioavailability of haem arginate is comparable to that of methaemalbumin, the natural form of transport of haem, it is effective both during remission and an acute attack. In both cases, but especially during an acute attack, hemin infusions are likely to correct the urinary excretion of delta-amino-laevulinic acid and porphobilinogen, the two main precursors whose accumulation is a characteristic of the disease. This applies for both acute intermittent porphyria and porphyria variegata.

Unlike older galenic preparations, haem arginate infusions do not cause any significant changes in the coagulation and fibrinolysis parameters in healthy volunteers. All these parameters have been shown to remain unchanged with the exception of the concentrations of factors IX and X, which fell temporarily by 10 to 15%.

After an intravenous infusion of hemin (3 mg/kg), the pharmacokinetic parameters (mean ± SD) observed in healthy volunteers and patients with porphyria are as follows:

C_(o) 60.0 ± 17 µg/ml

t_½ of elimination 10.8 ± 1.6 hours

Total plasma clearance 3.7 ± 1.2 ml/min

Volume of distribution 3.4 ± 0.9 l

After repeated infusions, the half-life of haem in the organism increases; it rises to 18.1 hours after the 4^th infusion.

Non-clinical data reveal no special effects for humans based on studies of safety pharmacology, single dose, repeated dose toxicity, mutagenicity, immunogenicity. Due to the human origin of hemin non-clinical studies with long-term treatment are not meaningful to perform therefore carcinogenic potential and toxicity to reproduction has not been investigated.