BENZOYL PEROXIDE FORMULATIONS Table II Comparative Acute Toxicity of Benzoyl Peroxide Formulations, 10 Per Cent 537 Formulation Dose Number of Deaths/ ml/kg Animals Total Animals LD50 (95 Per cent C.L.) mg/Kg 25 16.5 12.5 l0 25 16.5 12.5 l0 Control (vehicle) 0 10 10/10 10 8/10 10 3/10 10 0/10 10 10/10 10 9/10 10 7/10 lO 1/lO lO oho 14.07 (12.73-15.56) 12.09 (10.88-13.44) ACUTE LD50 Animals which received the test formulations were lethargic, prostrate, and exhibited evidence of labored respiration within 4 h. Changes in the general appearance and be- havior were more pronounced at the higher dose levels, especially for animals who died during the study. The mortalities occurred in a dose-response pattern for calcula- tion of an oral LD•0 for the various benzoyl peroxide formulations. The acute oral toxicity is expressed in Table II. There were no mortalities for the vehicle treated ani- mals. Formulation A was less toxic (not significant) from formulation C. OCULAR IRRITATION Conjunctival congestion observed at the l- through 24-h period was high in incidence for all treatment groups. Beginning on Day 7 through Day 21, minimal to moderate conjunctival congestion at a high to moderate incidence was observed for all test groups which received benzoyl peroxide formulations. Eyes which received the 10 per cent concentration exhibited severe conjunctival congestion at a high incidence on Days 7, 14 and 21, minimal conjunctival congestion was observed at the 1-h observa- tion period for the Day 0 controls. Thereafter, variable instances of minimal con- junctival congestion at a low to moderate incidence was observed for the Day 0 con- trols. Likewise, Day 1 controls and untreated controls exhibited minimal conjunctival congestion at a low to moderate incidence throughout the entire test period (Table III). There was less severity for A after 24 h than for formulation C. Moderate conjunctival swelling at a high incidence was observed in the 5-min and 24-h wash groups which received 10 per cent benzoyl peroxide for the 1-through 72-h observation period. At the 1-h observation period, moderate conjunctival swelling at a high incidence was observed for the 20-sec wash group for eyes which received the 10 per cent formulation thereafter, the same eyes exhibited minimal conjunctival swell- ing at a high incidence through the 72-h observation period at which time swelling was not observed for the remainder of this treatment group. For the 5-min and 24-h wash groups in eyes which received 10 per cent benzoyl peroxide on Days 7 and 14, minimal conjunctival swelling at a low to moderate incidence was observed, while no swelling

538 JOURNAL OF THE SOCIETY OF COSMETIC CHEMISTS Table III Conjunctival Congestion for Rabbits After Single Topical Ocular Instillat!on of Benzoyl Peroxide 10 Per Cent Wash Conjunctival Congestion Formulation Time c 1 h 24 h 48 h 72 h 7 day 14 day 2 ! day A 20 sec A 5 min A 24h C 20 sec C 5 min C 24h Day 0 Controls Day 0 Day 1 Controls Day 1 Untreated Controls -- •a 6.0 6.0 5.3 6.0 2.3 3.0 1.0 Inc? 6/6 6/6 6/6 6/6 5/6 6/6 3/6 • 6.0 6.0 6.0 6.0 4.0 4.0 3.5 Inc. 6/6 6/6 6/6 6/6 6/6 4/4 • 4/4 x 6.0 6.0 6.0 5.7 4.7 3.7 2.7 Inc. 6/6 6/6 6/6 6/6 6/6 6/6 6/6 • 6.0 6.0 6.0 5.7 5.3 4.0 5.0 Inc. 6/6 6/6 6/6 6/6 6/6 6/6 6/6 • 6.0 6.0 6.0 6.0 6.0 5.3 6.0 Inc. 6/6 6/6 6/6 6/6 6/6 6/6 6/6 x 6.0 6.0 6.0 6.0 6.0 5.0 5.3 Inc. 6/6 6/6 6/6 6/6 6/6 6/6 5/6 • 2.3 1.3 0.0 0.0 0.0 1.3 0.3 Inc. 6/6 3/6 0/6 0/6 0/6 4/6 1/6 • 0.0 0.7 0.3 0.0 0.3 2.3 0.7 Inc. 0/6 2/6 1/6 0/6 1/6 5/6 2/6 • 1.0 0.0 0.7 0.3 0.3 1.7 0.0 Inc. 3/6 0/6 2/6 1/6 1/6 5/6 0/6 •Maximum score: Congestion = 6. Mean score calculated by summing individual scores and dividing by the number of observations. bNumber of eyes with response/number of eyes in test group. qnterval of time after dosing until eye was washed. dNumber less than 6 indicates mortality not related to treatment. was observed for the 5-min wash group at the 21-day observation period but a single instance of minimal conjunctival swelling was observed for the 24-h wash group. Moderate conjunctival swelling at a high incidence was observed at the 1-through 72-h observation period for all 3 treatment groups receiving 10 per cent formulations. On Day 7, minimal conjunctival swelling at a high incidence was observed for the 20-sec wash group, while moderate conjunctival swelling at a high incidence was observed for the 5-min and 24-h wash groups for eyes which received the benzoyl peroxide formula- tions. Swelling was not observed for any control eyes (Table IV). Swelling was less severe for A after 24 h than for C. Moderate conjunctival discharge at a high incidence was observed at the 1- and 24-h observation periods for 3 treatment groups receiving the benzoyl peroxide formula- tions. For the 20-sec wash group, minimal conjunctival discharge at a high incidence was observed at the 48-h and 72-h observation periods with a discharge not being ob- served for the remainder of the test period. For the 5-min wash group, moderate con- junctival discharge at a high incidence was observed at the 48-h and 72-h observation periods with minimal conjunctival discharge at a low to moderate incidence being ob- served on Days 7 and 14 and with discharge being absent on Day 21. In the 24-h wash group, moderate conjunctival discharge at a high incidence was observed at the 48- and