Effect of isotretinoin on experimentally induced comedones.

The effect of isotretinoin on experimentally induced comedones was studied by means of histoplanimetry and scanning electron microscopy (SEM). To induce comedone formation, insoluble cutting oil was applied to the ventral surface of the ears of rabbits for 2 weeks. After comedones formed, isotretinoin was fed to the rabbits by a feeding tube, daily, for 4 weeks. A low dose (2.0 mg/kg) and a high dose (20.0 mg/kg body weight) were selected for two different groups. Soybean oil served as the vehicle. Histoplanimetrically, the high-dose group showed a significant decrease in size of comedones when compared to the control group and the low-dose group [P less than 0.005], and in the high-dose group, the follicular lumen contained a small number of loose, non-adherent, horny cells. Upon SEM examination, the comedones were seen to have a 'chrysanthemum' appearance before treatment. After treatment, the high- and low-dose groups both showed evidence of the elimination of comedones on three-dimensional analysis.