indication

For the treatment of moderate plaque psoriasis in adults.

pharmacology

Calcipotriene is a synthetic analog of vitamin D. In humans, the natural supply of vitamin D depends mainly on exposure to the ultraviolet rays of the sun for conversion of 7-dehydrocholesterol to vitamin D3 (cholecalciferol) in the skin.

mechanism of action

The precise mechanism of calcipotriol in remitting psoriasis is not well-understood. However, it has been shown to have comparable affinity with calcitriol for the Vitamin D receptor, while being less than 1% as active as the calcitriol in regulating calcium metabolism. The Vitamin D receptor (VDR) belongs to the steroid/thyroid receptor superfamily, and is found on the cells of many different tissues including the thyroid, bone, kindney, and T cells of the immune system. T cells are known to play a role in psoriasis, and it is thought that the binding of calcipotriol to the VDR modulates the T cells gene transcription of cell differentiation and proliferation related genes.

toxicity

Topically applied calcipotriene can be absorbed in sufficient amounts to produce systemic effects. Elevated serum calcium has been observed with excessive use of calcipotriene.

biotransformation

Hepatic. Calcipotriene metabolism following systemic uptake is rapid, and occurs via a similar pathway to the natural hormone. The primary metabolites are much less potent than the parent compound.

absorption

Clinical studies with radiolabeled ointment indicate that approximately 6% (+3%, SD) of the applied dose of calcipotriene is absorbed systemically when the ointment is applied topically to psoriasis plaques or 5% (+2.6%, SO) when applied to normal skin.

route of elimination

The active form of the vitamin, 1,25-dihydroxy vitamin D3 (calcitriol), is known to be recycled via the liver and excreted in the bile. There is evidence that maternal 1,25-dihydroxy vitamin D3 (calcitriol) may enter the fetal circulation, but it is not known whether it is excreted in human milk.

drug interactions

Alfacalcidol: Vitamin D Analogs may enhance the adverse/toxic effect of other Vitamin D Analogs. Avoid combined use of multiple vitamin D analogs (at pharmacologic doses). Prescribing information for calcitriol, doxercalciferol, paricalcitol, and alfacalcidol each specifically cautions against such combined use.

Aluminum hydroxide: Vitamin D Analogs may increase the serum concentration of Aluminum Hydroxide. Specifically, the absorption of aluminum may be increased, leading to increased serum aluminum concentrations. Avoid chronic and/or excessive use of aluminum and aluminum-containing products in patients who are also taking vitamin D analogs. Any patients consuming such a combination should be monitored closely for aluminum status and signs/symptoms of aluminum-related toxicities.

Cholecalciferol: Vitamin D Analogs may enhance the adverse/toxic effect of other Vitamin D Analogs. Avoid combined use of multiple vitamin D analogs (at pharmacologic doses). hough not specified in the prescribing information for calcipotriene, cholecalciferol, and ergocalciferol, each contains warnings regarding the potential for vitamin D toxicity.

Orlistat: Orlistat may decrease the serum concentration of fat soluble vitamins like vitamin D. Hence, this applies to calcipotriol, a synthetic derivative of vitamin D. Administer oral fat soluble vitamins at least 2 hours before or after the administration of orlistat. Avoid concomitant administration due to the risk of impaired vitamin absorption. Similar precautions do not apply to parenterally administered fat soluble vitamins.

Sucralfate: Vitamin D Analogs may increase the serum concentration of Sucralfate. Specifically, the absorption of aluminum from sucralfate may be increased, leading to an increase in the serum aluminum concentration. Avoid chronic and/or excessive use of aluminum and aluminum-containing products (such as sucralfate) in patients who are also taking vitamin D analogs. Any patients consuming such a combination should be monitored closely for aluminum status and signs/symptoms of aluminum-related toxicities.