Protection against the photosensitized skin irritancy of chlorpromazine by cyclodextrin complexation.

The efficacy of three types of cyclodextrins (CyDs) to reduce skin irritation in guinea pigs caused by photoirradiated chlorpromazine (CPZ) was in the order of beta-greater than gamma-much greater than alpha-CyD, depending upon the magnitude of the stability constant of the CPZ-CyD complexes. The inhibitory effects of CyDs may be attributable to the alteration in the photochemical reactivity of CPZ through inclusion complexation. By the photoirradiation of CPZ in the presence of CyDs, promazine, which is less toxic than CPZ, was produced and the yield decreased in the order of beta-greater than gamma-much greater than alpha-CyD. These results clearly indicate that beta-CyD complexation is particularly useful to reduce the CPZ-photosensitized damage to skin.