"Sublingual immunotherapy for allergic rhinitis" Cochrane Rev 2010.

Suzana Radulovic, MD, PhD, of St. Thomas' Hospital in London, England, and colleagues reported in the Cochrane Review an analysis of 60 trials found that SLIT treatment was associated with a significant reduction in symptoms and medication requirements when compared with placebo.  Cochrane Review is a widely respected peer reviewed publication that often attempts to analyze other unrelated studies to objectively determine if the literature supports or does not support a conclusion in medicine and in the care of patients.

"These data continue to support the clinical efficacy of sublingual immunotherapy for allergic rhinitis," Radulovic and co-authors wrote.

SLIT involves giving small but increasing doses of the allergen under the tongue as immunotherapy in either pill or drop form. It's more commonly used in patients who are refractory to treatment with antihistamines and nasal corticosteroids.

The review follows a meta-analysis done in 2003, which also suggested that sublingual therapy was effective, but the findings were based on a smaller number of trials. Much more evidence has accumulated since then, the researchers said.

In their current review, which added 38 trials including those involving pollen, dust mites, and cat allergens for a total of 60 studies, Radulovic and colleagues found a significant reduction in symptoms and medication requirements in patients on sublingual therapy compared with placebo (P<0.00001 for both).

"The overall results of the meta-analysis differ little from those seen in 2003," they wrote, "with the overall effect for symptom scores being of a similar magnitude, with tighter confidence intervals reflecting the greatly increased number of study subjects."

In terms of safety, the researchers said that local reactions were common and reported more frequently among those on sublingual immunotherapy compared with placebo.

But none of the trials reported severe systemic reactions or anaphylaxis to SLIT, and none of the systemic reactions required the use of adrenaline, they added. Systemic reactions were largely confined to upper respiratory tract -- although they were more frequent among patients on sublingual therapy.

"SLIT remains a safe treatment with an extremely low incidence of significant side effects," the authors wrote.

When they looked at the results by age, the researchers found that the SLIT treatment was significantly effective for both adults and children (P=0.001 and P<0.00001, respectively).

"SLIT represents a particularly attractive alternative to injection immunotherapy [among children] and our findings are entirely consistent with those reported elsewhere," Radulovic and co-authors commented.

They also found that doses under 5 mcg were not significantly effective, while doses higher than that level -- and those greater than 20 mcg -- were effective for allergic rhinitis.

The length of treatment may also be important, the researchers added. The study showed a trend in symptom score reduction in trials that latest for longer than 12 months.

"Indeed, SLIT is now given for longer time periods, and more recent studies have shown that treatment for longer than 12 months provides consistent clinical improvement in symptom and medication scores," the group wrote.

They noted that there were too few studies to compare sublingual immunotherapy directly with subcutaneous immunotherapy -- so more head-to-head trials are needed.

Still, Radulovic and colleagues concluded that sublingual therapy is "now established as a viable alternative to allergen injection immunotherapy, with a significantly lower risk profile and, on the basis of meta-analyses, little difference in overall efficacy."
http://www.medpagetoday.com/AllergyImmunology/Allergy/23794