Acitretin is all-Trans-9-(4-methoxy-2, 3, 6¬ trimethylphenyl)-three, 7-dimethyl-2, 4, 6, 8-nonatetraenoic acid. It is a metabolite of exterminate and is related to both retinoic acid and retinol (vitamin A). It is taken orally, and is typically used for psoriasis. The mechanism of action of is unknown. However it is believed to work by targeting specific receptors (retinoid receptors such as RXR and RAR) in the skin, which help normalize the growth cycle of skin cells. Studies on nuclear retinoic acid receptors have shown that acitretin activates all 3 receptor subtypes (RAR-alpha, -beta, and -gamma) without measurable receptor binding; this paradox remains unexplained.

7Z-Calcipotriol is an isomeric impurity in vitamin D analog calcipotriol. Synthesis of 7Z-Calcipotriol was disclosed by Japanese company Kuraray Co in a patent application JP 06316558.

Calcitriol is vitamin D3. Vitamin D is important for the absorption of calcium from the stomach and for the functioning of calcium in the body. Calcitriol is used to treat hyperparathyroidism (overactive parathyroid glands) and metabolic bone disease in people who have chronic kidney failure and are not receiving dialysis. Calcitriol is also used to treat calcium deficiency (hypocalcemia). The early signs and symptoms of vitamin D intoxication associated with hypercalcemia include: weakness, headache, somnolence, nausea, vomiting, dry mouth, constipation, muscle pain, bone pain and metallic taste. Cholestyramine has been reported to reduce intestinal absorption of fatsoluble vitamins; as such it may impair intestinal absorption of Calcitriol. Ketoconazole may inhibit both synthetic and catabolic enzymes of calcitriol.

Methoxsalen — also called xanthotoxin, marketed under the trade names Oxsoralen, Deltasoralen, Meladinine — is a drug used to treat psoriasis, eczema, vitiligo, and some cutaneous lymphomas in conjunction with exposing the skin to UVA light from lamps or sunlight. Methoxsalen modifies the way skin cells receive the UVA radiation, allegedly clearing up the disease. The dosage comes in 10 mg tablets, which are taken in the amount of 30 mg 75 minutes before a PUVA (psoralen + UVA) light treatment. Chemically, methoxsalen belongs to a class of organic natural molecules known as furanocoumarins. They consist of coumarin annulated with furan. It can also be injected and used topically. The exact mechanism of action of methoxsalen with the epidermal melanocytes and keratinocytes is not known. The best known biochemical reaction of methoxsalen is with DNA. Methoxsalen, upon photoactivation, conjugates and forms covalent bonds with DNA which leads to the formation of both monofunctional (addition to a single strand of DNA) and bifunctional adducts (crosslinking of psoralen to both strands of DNA) Reactions with proteins have also been described. Methoxsalen acts as a photosensitizer. Administration of the drug and subsequent exposure to UVA can lead to cell injury. Orally administered methoxsalen reaches the skin via the blood and UVA penetrates well into the skin. If sufficient cell injury occurs in the skin, an inflammatory reaction occurs. The most obvious manifestation of this reaction is delayed erythema, which may not begin for several hours and peaks at 48–72 hours. The inflammation is followed, over several days to weeks, by repair which is manifested by increased melanization of the epidermis and thickening of the stratum corneum. The mechanisms of therapy are not known. In the treatment of vitiligo, it has been suggested that melanocytes in the hair follicle are stimulated to move up the follicle and to repopulate the epidermis. In the treatment of psoriasis, the mechanism is most often assumed to be DNA photodamage and resulting decrease in cell proliferation but other vascular, leukocyte, or cell regulatory mechanisms may also be playing some role. Psoriasis is a hyperproliferative disorder and other agents known to be therapeutic for psoriasis are known to inhibit DNA synthesis. The most commonly reported side effect of methoxsalen alone is nausea, which occurs with approximately 10% of all patients. This effect may be minimized or avoided by instructing the patient to take methoxsalen with milk or food, or to divide the dose into two portions, taken approximately one-half hour apart. Other effects include nervousness, insomnia, and psychological depression.

Etretinate (trade name Tegison) is a medication developed by Hoffmann–La Roche that was approved by the FDA in 1986 to treat severe psoriasis. It is a second-generation retinoid. It was subsequently removed from the Canadian market in 1996 and the United States market in 1998 due to the high risk of birth defects. Etretinate remains on the market in Japan as Tigason. The mechanism of action of etretinate is still incompletely understood although, like retinoic acid, it is thought to interfere with the terminal differentiation of keratinocytes. Etretinate activates retinoid receptors, causing an induction of cell differentiation, inhibition of cell proliferation, and inhibition of tissue infiltration by inflammatory cells.

Trioxsalen (trimethylpsoralen, trioxysalen or trisoralen) is a furanocoumarin and a psoralen derivative. It is obtained from several plants, mainly Psoralea corylifolia. Like other psoralens it causes photosensitization of the skin. It is administered either topically or orally in conjunction with UV-A (the least damaging form of ultraviolet light) for phototherapy treatment of vitiligo1 and hand eczema.2 After photoactivation it creates interstrand cross-links in DNA, which can cause programmed cell death unless repaired by cellular mechanisms. In research it can be conjugated to dyes for confocal microscopy and used to visualize sites of DNA damage.3 The compound is also being explored for development of antisense oligonucleotides that can be cross-linked specifically to a mutant mRNA sequence without affecting normal transcripts differing at even a single base pair.Trioxsalen was discontinued by the manufacturer in December 2002.

Dithranol (INN) or anthralin (USAN and former BAN) is a Hydroxyanthrone, anthracene derivative, medicine applied to the skin of people with psoriasis. It is available as creams, ointment or pastes in 0.1 to 2% strengths. The terms dithranol and anthralin are sometimes used synonymously. Anthralin cream is a topical antimitotic. It works by slowing the reproduction of skin cells, precise mechanism of anti-psoriatic action is not yet fully understood. However, numerous studies have demonstrated anti-proliferative and anti-inflammatory effects of anthralin on psoriatic and normal skin. The anti-proliferative effects of anthralin appear to result from both an inhibition of DNA synthesis as well as from its strong reducing properties. Recently, anthralin’s effectiveness as an anti-psoriatic agent has also been in part attributed to its abilities to induce lipid peroxidation and reduce levels of endothelial adhesion molecules which are markedly elevated in psoriatic patients. Unlike retinoids and PUVA, anthralin does not inhibit liver microsomal enzyme activity; consequently, the likelihood of adverse drug interactions is greatly reduced when other agents are administered concomitantly with anthralin.

Talcalcitol is a synthetic analogue of vitamin D3. Tacalcitol has been developed by Teijin in Japan with the aim of maintaining the potent cell-regulating properties of calcitriol without the calcium-related adverse effects. Tacalcitol differs structurally from calcitriol by hydroxylation in the 24 position instead of the 25 position. Tacalcitol can influence the principal pathogenetic factors of psoriasis by inducing normalisation of keratinocyte differentiation, performing an anti-proliferative action and finally modulating the inflammatory response. Tacalcitol has been launched as an ointment formulation for the treatment of psoriasis in various countries. High-dose formulations (ointment and lotion) are available in Japan.

Ethyl fumarate is an anti-psoriatic agent. Its salts are used for the treatment of severe psoriasis (Fumaderm formulation). The mechanism of its action is unknown.

Bergapten, known as 5-methoxypsoralen, a cumarine-derivate compound, presents in many fruits and vegetables. It has shown antitumor effects in a variety of cell types. The key target of bergapten action in breast cancer cells was identified the oncosuppressor gene PTEN (phosphatase tensin homolog deleted from chromosome 10); bergapten by inducing PTEN expression, produces autophagy in breast cancer cells. Besides, bergapten is under investigation in clinical trial phase III for patients with severe generalized atopic dermatitis.