Speaking at Skin Spectrum Summit in Montreal, Toronto dermatologist Dr. Gary Sibbald presented several pearls for the treatment of patients with psoriasis.
Topical treatments for psoriasis can be compounded into a wide range of vehicles with different advantages, said Dr. Sibbald. Occlusive vehicles, such as ointments or patches, have an anti-psoriatic effect on their own beyond the active agent they carry, he said. As an example, he detailed a study that compared a new self-adhesive betamethasone 0.1% valerate patch—indicated for mild to moderate plaque psoriasis on the elbows and knees—to the same drug concentration in a cream vehicle. The study found the patch to be twice as effective.
Choosing a topical steroid
Topical steroids are a first line treatment for acute and flaring psoriasis, but the effective potency varies not only by which steroid is chosen, but also the site where the topical therapy is being applied, Dr. Sibbald said. Using the forearm as a baseline of one for evaluating relative percutaneous absorption, other parts of the body may have widely lower absorption (such as 0.14 on the plantar areas) or widely higher absorption (such as 42.00 on the scrotum). The potency of the chosen steroid (relative to hydrocortisone 1%) needs to be multiplied by the relative percutaneous absorption of the target area to ensure the results desired can be obtained and the clinician is not under-treating or over-treating the area.
As well, Dr. Sibbald advised against selecting steroids with relative potencies higher than six, since they can quickly result in tachyphylaxis and resistance to the treatment, unnecessarily removing a stronger option from the clinician’s toolbox.
Regarding allergic reactions to topical steroids, Dr. Sibbald said it is important to remember that all steroids fall into one of four groups—A, B, C, or D. If a patient has developed an allergy, they will react to any steroid in the same group.
Vitamin D derivatives such as calcipotriol—in combination with a steroid or not—can be beneficial for reducing the need for steroids, said Dr. Sibbald. Many patients, particularly those living in cold climates or those with dark skin, are low in vitamin D in general and may benefit from a supplement.
Tazarotene and other vitamin A derivatives may produce an increased susceptibilty to sunlight that patients should be made aware of, Dr. Sibbald said. These agents should also not be used during pregnancy.
Coal tar is anti-proliferative and keratolytic, and can be easily combined with topical steroid treatment but some patients find it unpleasant to use or object to the smell, said Dr. Sibbald. A more refined form, liquor carbonis detergens (LCD), may be more acceptable to patients, but is less effective. A 20% formulation of LCD is comparable to a 4% coal tar formulation. Either form may aggravate acne or cause folliculitis, however, he said.
Associations and pitfalls
Scalp psoriasis may be distinguished from sebhorreic dermatitis by checking the margins, Dr. Sibbald said. “If you can draw a line around the lesion, it is scalp psoriasis,” he said. Sebhorreic dermatitis has much less clearly defined margins. Patients should also be cautioned against trying to descale scalp psoriasis, as any scratching or trauma could trigger the Koebner phenomenon and produce a worsening of the psoriasis, he said.
Psoriasis should also be considered in abnormal toenails, said Dr. Sibbald. “Only 50 per cent of ‘funny toenails’ are fungal,” he said.
Systemically, steroids should not be used in psoriasis because there is a high risk of a strong rebound flare when treatment ends, Dr. Sibbald said.
Systemic biologic therapies are extremely effective, but most health systems want patients to have failed two other systemic agents first, he said, and some biologics can be prohibitively expensive even for patients on drug plans.