The Effect of Shampoos on Rabbit Ileum in Vitro Compared to Eye Irritancy in Vivo

The concentrations of 5 antidandruff, 7 adult, and 11 baby shampoos required to block spontaneous contractions of rabbit isolated ileum by 50% (EC 50 ) in vitro were determined. In general, antidandruff shampoos were the most potent and baby shampoos least potent in this test. The in vitro ileum EC 50 s for antidandruff and adult shampoos correlated well with ocular irritancy determined in vivo from samples diluted to 20%. Correlation between in vitro ileum EC 50 s and in vivo irritancy was poor for baby shampoos, but in vivo irritancy for these samples was barely detectable 24 hours after instillation. The findings suggest that the ileum model may be useful as a possible alternative to in vivo testing for some formulated products, particularly where in vivo irritancy might be more than minimal.