Retinoids
The Retinoids are a class of chemical compounds that are related chemically to vitamin A. Retinoids are used in medicine, primarily due to the way they regulate epithelial cell growth.
Normal function in body
- Has Roles in vision
- Regulation of cell proliferation and differentiation
- Growth of bone tissue
- Immune function
- Activation of tumor suppressor genes.
Research is also being done into their ability to treat skin cancers. Currently 9-cis retinoic acid may be used topically to help treat skin lesions from Kaposi's sarcoma.
Types
There are three generations of Retinoids:
- First generation Retinoids: which include retinol, retinal, tretinoin (Retin-A), isotretinoin and alitretinoin.
- Second generation Retinoids: which include etretinate and its metabolite acitretin.
- Third generation Retinoids: which include tazarotene , bexarotene and Adapalene
Structure
- First and Second generation Retinoids are able to bind with several retinoid receptors due to the flexibility imparted by their alternating single and double bonds.
- Third generation Retinoids are less flexible than First and Second generation Retinoids and therefore, interact with fewer retinoid receptors.
Medical Uses
- Inflammatory skin disorders (ex: acne)
- Skin cancers
- Disorders of increased cell turnover (ex: psoriasis)
- Photoaging
- Acne Vulgaris
- Photoaging/Intrinsic Aging
- Psoriasis
- Actinic keratosis and actinic lentigines
- Premalignant Oral Lesions
- Rosacea
- Verruca
- Hypertrophic Scars, Keloids, Acne Scars, and Striae
- Cutaneous Lichen Planus
- Melasma
- Darier's Disease
- Wound Healing
- Granular Parakeratosis
- Multiple Miliary Osteoma Cutis
- Alopecia Areata
- Keratosis Pilaris (KP)
- Acanthosis Nigricans (AN)
Toxicity
Toxic effects occur with prolonged high intake (in children 25,000-500,000 IU daily). A medical sign of chronic poisoning is
· The presence of painful tender swellings on the long bones.
· Anorexia
· Bleeding
· General malaise
· Death may occur
· Chronic overdose also causes an increased liability of biological membranes and of the outer layer of the skin to peel.
· Recent research has suggested a role for retinoids in cutaneous adverse effects for a variety of drugs including the Antimalarial drug proguanil. It is proposed that drugs such as proguanil act to disrupt retinoid homeostasis.
Reverences
· The Pharmacological Basis of Therapeutics -Goodman & Gilman 10th EDT.
· Clinical Pharmacology -P.N. Bennett & M.J. Brown
