Is Fleming's lysozyme an analgesic agent? An experimental reappraisal of clinical data.

Hen egg white lysozyme (Fleming's lysozyme) was tested for antinociceptive activity in rats against foot hyperalgesia provoked by a subplantar injection of a number of irritants: arachidonic acid, brewer's yeast, carrageenan, kaolin, mepartricin and rabbit anti-rat serum (Randall-Selitto method). The compound was active when given p.o., i.m. or i.v. (100-200-400 mg/kg) as well as when injected locally in the foot pad concurrently with the irritant (1-2-4 mg/rat). Lysozyme decreased the sensitivity of the inflamed paw to the nociceptive stimulation, left unmodified the sensitivity of the normal paw and did not reduce the oedema of the inflamed paw. It differed in its activity from steroidal and non-steroidal anti-inflammatory drugs and from central analgesics that were used as standard reference drugs. Its activity was not shared by hen egg white and ovalbumin. Contrary to dextran, lysozyme i.p. did not induce anaphylactoid reactions. Lysozyme did not provoke tolerance and did not interfere with the antinociceptive activity of morphine. The results are in agreement with clinical data published years ago. Lysozyme was claimed to be an active agent against herpes zoster and cancer pain.