Atopic dermatitis tx options grow

September 1, 2004

Victoria, British Columbia - Antihistamines are effective adjunctive therapy in the treatment of atopic dermatitis (AD), according to research presented at the annual meeting of the Canadian Dermatology Association.

Victoria, British Columbia - Antihistamines are effective adjunctive therapy in the treatment of atopic dermatitis (AD), according to research presented at the annual meeting of the Canadian Dermatology Association.

Dr. Ron Vender, associate clinical professor of medicine at McMaster University, division of dermatology, presented a literature review of studies involving antihistamines to treat AD at a poster session. The inflammatory skin disorder affects about 10 percent to 15 percent of children worldwide and is growing in prevalence. It affects all ages and occurs particularly in those with a personal or family history of atopy.

"The additive effect is that it decreases the itching that the condition can bring on," says Dr. Vender. "Because the itching decreases, it lessens the possibility of the barrier to the skin being broken. When that barrier is broken, more allergens are introduced and there is increased water loss from the skin. A secondary infection can occur as well as a flare of the AD."

New agents, such as tacrolimus and pimecrolimus, referred to as topical immunomodulators, are being prescribed to treat atopic dermatitis, and antihistamines can act in conjunction with those agents to treat the pruritus associated with the condition, Dr. Vender says.

New research, new results Studies that have looked at the pathogenesis of AD found that levels of histamine were raised in the skin and in the peripheral blood of patients with atopic eczema; however, more recent evidence does not support the role of histamine in the pathogenesis of pruritus in AD.

Dr. Vender and fellow researchers conducted a MEDLINE search of studies involving first-generation, second-generation and third-generation antihistamines to treat AD to determine the clinical evidence to support the effectiveness and use of the agents. The 24 studies that wereincluded had one or several of the following characteristics: double-blind, randomized, placebo-controlled, crossover or unknown. Most of the included studies had anywhere from 15 to 50 patients enrolled. The duration of the trials ranged from two days to 12 weeks.

Of the 24 studies included, the majority (17) supported efficacy of antihistamines in the treatment of AD, while seven did not, with almost all of the studies that did not support efficacy involving first-generation antihistamines.

"The overall response is favorable in terms of the studies we have looked at," Dr. Vender says. "Larger studies can be done to examine their therapeutic efficacy, particularly with the newer antihistamines. This would give us more insight into the mechanism of action of antihistamines as they relate to AD."

One of the drawbacks of the first-generation antihistamines is the somnolence and anti-cholinergic effects that they produce. The second-generation antihistamines represent an improvement over the first-generation antihistamines because they do not cross the blood-brain barrier and produce fewer depressive effects on the central nervous system. The third-generation agents offer effects in addition to histamine antagonism, such as the inhibition of eosinophil migration/degranulation and inhibition of mediator release.

Patients should be advised to avoid potential triggers of AD such as certain foods and chemicals, such as skin care and laundry products, as well as allergens such as pollen, dust mites and mold. Prostaglandins have also been explored as playing a role.

In terms of an appropriate antihistamine, Dr. Vender suggests the sedating agents should only be taken in the evening, and the non-sedating antihistamines should be taken during the day to avoid drowsiness.