Chlorpromazine Photosensitivity in Mice: Its Action Spectrum and the Effect of Anti-Inflammatory Agents

SUMMARY.— The photosensitizing action spectrum of chlorpromazine (CP) has been investigated in hairless mice. Our results suggest that CP photosensitivity in this animal has a broad action spectrum in the longwave u.v. spectrum, viz. from 330 to 370–380 nm., with peak activity at wavelengths just above normal sunburn wavelengths. In other words we could establish photosensitization activity of the drug at wavelengths which it is known to absorb that are longer than about 320 nm.; we were unable to demonstrate a lowering of threshold response in the presence of the drug when normal sunburn wavelengths were used. Both soya bean trypsin inhibitor and e‐amino‐n‐caproic acid inhibited the specific photosensitivity reactions of immediate or early onset, due to CP. This result suggests that the reaction may be mediated through the action of a plasmin or “protease‐polypeptide” system. It is tentatively suggested that the mediators causing the normal sunburn reaction may differ from those causing CP photosensitivity.