Haem arginate improves hepatic oxidative metabolism in variegate porphyria.

1. The elimination of antipyrine was investigated before and after intravenous administration of haem arginate (3 mg haem kg-1 day-1 on three or four successive days) to six patients with variegate porphyria in remission. 2. Haem arginate decreased the faecal content of protoporphyrin from 557 +/- 91 to 118 +/- 32 (mean +/- s.e. mean) and of coproporphyrin from 144 +/- 19 to 19 +/- 3 nmol g-1 dry weight. 3. Before haem treatment antipyrine elimination half-life was long (30.5 +/- 5.6 h), but the treatment decreased it to 6.3 +/- 0.8 h. Antipyrine clearance increased from 0.25 +/- 0.05 to 1.03 +/- 0.11 ml min-1 kg-1 (P less than 0.001), being 4.6 times higher after haem arginate infusions. 4. The volume of distribution of antipyrine did not change. 5. The severe impairment of hepatic mixed function oxidase activity even in the symptomless stage of porphyria indicates cautious dosage of drugs primarily eliminated by hepatic oxidative reactions.