Pharmacokinetics of intravenously administered haem arginate

The pharmacokinetics of haem were investigated after intravenous administration of a therapeutic dose of haem arginate (3 mg haem kg-1) to four healthy volunteers and four symptomless porphyric patients. Plasma haem concentrations were measured also during a treatment course of four infusions in six patients with porphyria. Plasma haem concentrations declined monoexponentially over 48 h in both healthy volunteers and porphyric patients, with a mean +/- s.e. mean elimination half-life of 10.8 +/- 0.6 h. Other kinetic parameters were also similar in the two groups, total plasma clearance was 3.7 +/- 0.4 ml min-1 and volume of distribution was 3.37 +/- 0.34 l. In the multiple dose study the elimination half-life increased significantly, from 11.3 +/- 0.4 h to 18.1 +/- 1.4 h over 4 consecutive days. Plasma haemopexin values decreased with time after a single haem arginate dose. The infusion of haem arginate did not cause thrombophlebitis.