Psoriasis: Can Vitamin D analogues be the solution?

Vitamin D analogues are synthetic forms of vitamin D3. They are typically prescribed for psoriasis that is mild to moderate as an alternative to dermocorticoids. They act on the multiplication and maturation of keratinocytes. They are available in the form of creams, ointments or lotions. The two most commonly used forms are calcipotriol and calcitriol.

What are the molecular mechanisms behind its properties?

The molecular mechanisms are still somewhat poorly understood to explain the effect of vitamin D analogues on the multiplication and maturation of keratinocytes. Studies have shown that calcitriol inhibits the proliferation of T lymphocytes, particularly CD4+ and CD8+ T lymphocytes, by inducing early apoptosis. This helps to prevent the production of inflammatory molecules that will stimulate the proliferation of keratinocytes.

In common forms of the disease, the local application of an ointment based on analogues of vitamin D3 on the lesions remains the standard treatment. Calcipotriol or Daivonex is a synthetic extract of vitamin D, whose affinity for the receptor is similar. Side effects, particularly abnormalities in calcium metabolism, only occur in cases where the clinically recommended doses are exceeded, namely:

• 100 g of cream per week from the age of 16;

• 75 g/week between the ages of 12 and 16;

• 50 g/week between 6 and 12 years old.

Silkis is a calcitriol-based treatment that comes in the form of an ointment to be applied to areas affected by psoriasis. The dosage to be adhered to is an application twice a day, not exceeding 30 grams of ointment per day.

To mitigate the potential risk of interaction with phosphocalcic metabolism, the safe use of calcipotriol is permitted on a limited area, approximately 35% of the body surface.

Good to know: Combination with a dermocorticoid is possible, such as the case of betamethasone and calcipotriol. However, this prescription is recommended for a maximum duration of four weeks.

Whilst these treatments are effective, they also present dermatological side effects. Calcipotriol can, in some cases, cause perilesional erythema and tingling or burning sensations at the applied sites. Calcitriol has these same side effects but at a lower frequency, thus the use of calcitriol is recommended in sensitive skin areas, such as flexion zones, retro-auricular and facial areas.

Depending on the prescribed quantities, it is possible to observe irritative dermatitis in nearly 20% of cases. Contact allergic dermatitis, on the other hand, is less common. They are often accompanied by episodes of photosensitisation, particularly in patients undergoing UVB phototherapy.

During treatment, a transient and mild hypercalcaemia, with a twice-daily regimen of calcitriol, was observed in 5% of patients and resolved in four out of five individuals.

Pregnancy and breastfeeding are among the contraindications for treatment in the absence of sufficient data. Hypercalcaemia is also contraindicated as calcitriol or calcipotriol tend to increase calcium absorption. This situation can be dangerous, as an excessive level of calcium can lead to various health problems. Generally, it is advised to take the time to carefully read the list of contraindications mentioned on the product currently in use.

KÖRVER J. E. M. & al. A double-blind, randomized quantitative comparison of calcitriol ointment and calcipotriol ointment on epidermal cell populations, proliferation and differentiation. Therapeutics (2007).

MITRA A. & al. Immunomodulatory Mechanisms of Action of Calcitriol in Psoriasis. Indian Journal of Dermatology (2014).

Les traitements locaux. Association France Psoriasis (2016).