162 JOURNAL OF THE SOCIETY OF COSMETIC CHEMISTS 40 80 120 160 AREA/MOLECULE, [•' Figure 5. Surface pressure versus area per molecule for L-o•-dipalmitoyl lecithin on acetic acid- sodium acetate buffer (pH 5.9) at 25øC and ionic strength 0.1. Key: O, zero concentration of fluphenazine dihydrochloride, irradiated and nonirradiated I, 1 X 10-'•M fluphenazine dihydrochloride, nonirradiated &, 1 X 10-•M fluphenazine dihydrochloride, irradiated o IO 20 3o 40 50 TIME • MINU'TES Figure 6. Surface pressure versus time of irradiation of 1 X 10-4M solutions of promazine (&) chlorpromazine HC1 (O) and prochlorperazine diHC1 (I) at 25øC, pH 5.9, and ionic strength 0.1. Dashed line (---) indicates period after irradiation was stopped

PHOTOSENSITIZED REACTIONS 163 slower secondary change (Fig. 6). Promazine showed no surface pressure either before or after irradiation. It should be noted that chlorpromazine and prochlorperazine both have a chlorine substituent on the 2 position of the phenothiazine nucleus. They differ in their substituent on the 10 position (Table I). Promazine, on the other hand, is identical to chlor- promazine except for a hydrogen on the 2 position instead of a chlorine. Table I Phototoxic Index (PI)• of Six Phenothiazine Derivatives I R•0 Compound R•0 R2 PI Promazine --(CH2)aN(CHa)2 H 0 Chlorpromazinc --(CH2)aN(CHa)2 C1 60 Trifiupromazinc --(CH 2 )aN (CH a ) • CF a 0 Prochlorpcrazinc --(Ctt2),--•/N--CH• Cl 50 Trifluopcrazinc --(CH2) •--•_/N-- CHa CFa --300 0,, Fluphcnazinc --(CH2)•/N-- CH2-- CH2-- 0H CFa --25b +20c See text for definition and method of calculation. Value recorded initially. Value recorded after about 15 minutes. In contrast, all of the trifluoromethyl derivatives (triltuoperazine, triltupromazine, and fluphenazine) showed a rapid decrease in surface pressure which lasted from one to three minutes (Fig. 7). Trifluoperazine and triflupromazine, following this rapid period of change, exhibited a second, slow change which continued for the remainder of the irradiation period. Fluphenazine, however, after about 13 minutes of irradiation reversed its trend and showed a marked increase in surface pressure that persisted for about 25 minutes even though the irradiation lamp was turned off during part of that time. The maximum surface pressure reached by fluphenazine (about 15 minutes after irradiation was stopped) was almost 8 dynes higher than that recorded for the nonirradiated com- pound. The surface pressure of both the triflupromazine and trifluoper- azine solutions increased rapidly for about 25 minutes after the lamp was