<p>Isotretinoin produces its effects through altering progress through the cell cycle, cell differentiation, survival, and apoptosis. These actions reduce sebum production, preventing the blockage of pores, and growth of acne causing bacteria. Isotretinoin and 4-oxo-isotretinoin both significantly reduce the production of sebum. Isotretinoin has little to no affinity for retinol binding proteins (RBPs) and retinoic acid nuclear receptors (RARs). Tretinoin and 4-oxo-tretinion bind to the RAR-&gamma; receptor, which is suspected to be part of the action of acne treatment by isotretinoin. Isotretinoin induces apoptosis in sebocytes, leading to a decrease in sebum production. Isotretinoin also reduces the formation of comedones by reducing hyperkeratinization through an unknown mechanism. Isotretinoin does not directly kill bacteria but it does reduce the size of sebum ducts and makes the microenvironment less hospitable to acne causing bacteria. It may also increase immune mechanisms and alter chemotaxis of monocytes to reduce inflammation.</p>