Steroidal muscle relaxants might theoretically be contraindicated in acute
hepatic porphyrias.
Atracurium, on the other hand, has been proposed as the muscle relaxant of choice because of its extrahepatic degradation. To further investigate this problem, equipotent doses of
atracurium,
vecuronium, and
pancuronium were determined in male Sprague Dawley rats, using evoked electromyography. After this pilot study, 64 rats were anesthetized, mechanically ventilated, and randomly allocated to eight groups. Animals in groups 1 through 4 received an
intraperitoneal injection of
arachis-oil 20 h before the experiments. For groups 5 through 8, an experimental
porphyria was induced by use of the chemical substance
3,5-dicarbethoxy-1,4-dihydrocollidine (DDC), which was dissolved in
arachis-oil and given 20 h prior to the beginning of the study. Rats of groups 1 and 5 served as controls; they received saline and were not given muscle relaxants throughout the experiment. For groups 2 and 6,
atracurium was administered at a dosage of 4 mg/kg of
body weight, followed by a continuous infusion of 15 mg/kg/h. Animals of groups 3 and 7 received
vecuronium at a dosage of 1.5 mg/kg, followed by 7.5 mg/kg/h. For groups 4 and 8,
pancuronium was given (0.75 mg/kg and 2.5 mg/kg/h, respectively). At the end of the 3-h study period, the liver was perfused and excised, and urine was obtained. Activity of the hepatic
enzyme delta-aminolevulinic acid synthase (ALAS) and urinary concentrations of
delta-aminolevulinic acid (ALA) and
porphobilinogen (PBG) were determined.(ABSTRACT TRUNCATED AT 250 WORDS)