Is Fleming's lysozyme an analgesic agent? Experiments on mice

1. Antinociceptive activity of hen egg white lysozyme (Fleming's lysozyme) was determined against abdominal contractions provoked by irritants injected intraperitoneally into mice. Carrageenan (2 mg) (CA) injected with arachidonic acid (15 micrograms) (AA) or prostaglandins PGE1 or PGF2 alpha (0.04 ng), brewer's yeast (10 mg), caolin (10 mg), mepartricin (80 U) and phenylquinone (50 micrograms) were used as irritants. 2. Lysozyme was active at 400-800 mg/kg i.v. against CA + AA, CA + PG, brewer's yeast and caolin nociceptive stimulation. The compound was more effective against CA + AA than against CA + PG. Acetylsalicylic acid at 50-100-200 mg/kg p.o. was equally active against CA + AA and CA + PG. 3. Lysozyme was inactive in the tail pinch and hot plate tests that mainly detect central analgesics. 4. The results are discussed in relation to the claim advanced years ago that lysozyme is an effective analgesic agent in humans. The compound was found active against herpes zoster or cancer pain but did not find use despite the favourable reports presented. 5. The experimental results obtained on laboratory animals do not contradict the conclusions drawn after the clinical use of the compound.