- Hydroquinone / Tretinoin / Kojic Acid / Hydrocortisone
Hydroquinone is a topical depigmenting agent. It is structurally related to monobenzone, a potent depigmenting agent. Unlike monobenzone, depigmentation caused by hydroquinone is reversible. Hydroquinone is used for temporary bleaching of hyperpigmented skin conditions such as chloasma (melasma), freckles, and lentigines. Sunscreens must be used concomitantly with topical hydroquinone; several commercial preparations do contain a sunscreen agent. Hydroquinone is also used as an antioxidant for ether and in photographic development. Hydroquinone has been available since before 1938.
Tretinoin, also known as all-trans-retinoic acid (ATRA), is a naturally occurring derivative of vitamin A. As vitamin A (retinol) derivatives, retinoids are important regulators of cell reproduction, and cell proliferation and differentiation; however, unlike vitamin A, retinoids are not converted into rhodopsin, which is needed for night vision. Topical tretinoin is indicated in the treatment of mild to moderate acne (e.g., grades I-III) and photodamaged skin. Topical tretinoin has also been used in the symptomatic management of keratinization disorders such as ichthyosis and keratosis follicularis. Tretinoin represents a new class of anticancer drugs, differentiating agents. Oral tretinoin is used in the treatment of acute promyelocytic leukemia (APL) and is undergoing phase III investigation in the treatment of Kaposi’s sarcoma. In the treatment of APL, tretinoin offers a less toxic means to induce complete remission than conventional chemotherapy; however, approximately 25% of patients who receive tretinoin for the treatment of APL have experienced acute promyelocytic leukemia differentiation syndrome.
Kojic acid is a chelation agent produced by several species of fungi, especially Aspergillus oryzae, which has the Japanese common name koji. Kojic acid is a by-product in the fermentation process of malting rice, for use in the manufacturing of sake, the Japanese rice wine. It is a mild inhibitor of the formation of pigment in plant and animal tissues and is used in food and cosmetics to preserve or change colors of substances.
Hydrocortisone is a naturally occurring steroid hormone secreted by the adrenal cortex that has glucocorticoid and mineralocorticoid activity. Synthetic hydrocortisone is available pharmaceutically in a variety of rectal, parenteral, oral, and topical dosage forms. As a naturally occurring glucocorticoid that also has salt-retaining properties systemic hydrocortisone is used primarily as replacement therapy in adrenocortical deficiency states, and when emergency anti-inflammatory treatment is needed. Rectal hydrocortisone products are particularly useful in inflammatory gastrointestinal conditions limited to the rectum and anus. Systemic hydrocortisone may be used in many other allergic, immune, and inflammatory conditions in adult and pediatric patients; however, systemic corticosteroids that have more potent glucocorticoid activity and minimal mineralocorticoid activity, such as prednisone, are preferred for such uses, as they induce better response and reduce the risks of excess mineralocorticoid side effects. Systemic corticosteroids may be added to other long-term maintenance medications in the management of uncontrolled severe persistent asthma and short courses may be used for asthma exacerbations; however, systemic hydrocortisone is rarely used for these purposes. Topical hydrocortisone is considered low potency and is used in mild to moderate corticosteroid-responsive dermatoses, and many topical dosage forms are available without a prescription. Low potency topical corticosteroids are the safest for chronic use and may be used on the face or intertriginous areas, with occlusion, and in infants and young children.