Sorbent therapy of the porphyrias. II. Experimental plasma or hemoperfusion with a commercial charcoal cartridge.

We studied the ability of a commercial charcoal hemoperfusion cartridge (Hemosorba Hemoperfusion Cartridge, Asahi Medical Company) to adsorb the porphyrin precursors delta-aminolevulinic acid (ALA) and porphobilinogen (PBG) in vitro. For measurement of clearances or decreases in concentration of porphyrin precursor, indices of adsorptivity, solutions of porphyrin precursor were circulated from a reservoir through the cartridge and back to the reservoir. For determination of change in concentration of porphyrin precursor with time, the concentration of material in the reservoir was determined periodically. Clearances of porphyrin precursor were determined from their concentration in both the reservoir (maintained nearly constant by the periodic addition of solute) and the cartridge effluent. Clearances were independent of the nature of the medium (saline, 0.1 M phosphate buffer, pH 7.4, or human plasma), time (through 2 hr) and initial concentration of porphyrin precursor (3.0-10.3 mg/L for ALA, 1.5-3.6 mg/L for PBG). ALA clearances (ml/min) were 106 +/- 22, while maximal PBG clearances were never ascertained (greater than or equal to 310). The concentration of porphyrin precursor decreased rapidly during perfusion: about 82% and 98% of ALA and PBG, respectively, were removed in 5 minutes. Neither the clearances nor the concentration decreases were affected by the simultaneous presence in the solution of hematin (initial concentration of 50 mg/L), which itself had a clearance of 10.7 +/- 12.6 and only a modest concentration change with time (60-68% decrease in 40 min). Hemosorba cartridges adsorbed 650 mg ALA and 85 mg PBG without any appreciable change in adsorptivity. Hemoperfusion may be an appropriate adjunctive therapy, in combination with infusions of hematin, of particularly severe or refractory acute porphyric crises.