Ciliotoxicity of methyl- and propyl-p-hydroxybenzoates: a dose-response and surface-response study

The effect of methyl-p-hydroxybenzoate (methyl paraben, MHB) and propyl-p-hydroxybenzoate (propyl paraben, PHB) on ciliary beat frequency was investigated using surface-response methodology. Both compounds are shown to be ciliotoxic at concentrations equal to or lower than those in use for preserving aqueous formulations. The dose-response curves show the typical sigmoidal pattern. Interaction by the two compounds is evidenced by the curved response surface for ciliotoxicity.