Four consecutive stages of systemic isotretinoin action are described. In the description of pharmaceutical and pharmacokinetic stages, the attention was paid to issues of bioavailability, absorption mechanisms and biotransport of retinoids. The choice of gelatin capsules as the dosage form resulted from the absence of the oil phase in the tablet, that is essential to create an optimal pharmaceutical composition. In the presence of food, systemic exposure (AUC) increases by an average of 1.5 times for the lidose form and about 2.5 times for the usual form of isotretinoin. Dietary administration of isotretinoin increased its peak plasma concentrations (Cmax) 1.6 times and 2.7 times, respectively, for lidose and the usual form, compared with administration on an empty stomach. Genomic and non-genomic retinoid effects, implementation mechanisms of pleiotropic action on pathogenesis of acne are explained in the pharmacodynamical stage section. Genomic mechanism of action is realized by recognition and binding of trans-retinoid acid (TRA) with ligand-activated factors of transcription known as TRA-receptors (TrAR). Non-genomic action of retinoids includes mechanisms of modification of intracellular proteins` functions by attaching them with the rest of retinoic acid (protein retinoylation). The focus in describing of the clinical use of isotretinoin was on the tolerance of treatment. The concept of drug quality was detailed with examples of generic isotretinoin` drugs.