SLIT vs SCIT: A Q&A

Dr. Marple: In the US there was use of the sublingual approach by homeopaths, but the doses were quite low, and the studies relating to it weren’t of high quality. The doses being used in Europe were much higher and approximated those that were being given by subcutaneous routes. Over the past decade, rigorous clinical trials have demonstrated that when delivered in adequate doses, this was a viable form of antigen delivery. Now, SLIT is becoming more mainstream in the US.

How effective is SLIT compared with SCIT? How do the safety profiles compare?

Dr. Marple: The efficacy from this different route of delivery for immunotherapy appears in most outcome studies to be roughly equivalent to subcutaneous IT. While some studies fail to show significant benefit, a recent Cochrane meta-analysis demonstrated efficacy in control of rhinitis symptoms in patients older than 12 years. Further, there was a trend suggesting that better results were seen in studies that made use of higher doses of antigen, suggesting that total dose of antigen is important. Conversely, insufficient pediatric data were available to make an assessment. The huge difference is in the safety profile. This appears to be much safer than subcutaneous IT.

Dr. Morris: A Scandanavian study compared the effectiveness and safety of injection therapy with SLIT using birch pollen antigens. It was a placebo-controlled, double-blind, double-dummy trial. Both therapies showed superiority over placebo, and statistically there was no difference between subcutaneous and sublingual in terms of efficacy. However, safety was markedly better with sublingual. It’s the best-designed study we’ve had on this.

Are the same antigens used for SCIT and SLIT?

Dr. Levine: Yes. You have the same variety, and you can treat patients with a larger number of antigens using drops [SLIT] compared to the shots. With individual injections, there are limitations to what we normally mix together. For instance, some like to keep the mold antigens separate from the trees, grasses, and leaves. Others might want to keep dust separate from the animal antigens. And there is a limitation to how many injections patients will tolerate. Many will limit it to four injections, plus limit the number of antigens in each one of these injections. This is all in an effort to reduce adverse reactions. However, with SLIT there are so few reactions, we can actually use more antigens simultaneously safely. Typically, in our practice, we’ll mix as many as 20 antigens in a single bottle.

Does using SLIT require much training?

Dr. Marple: I would not like to lose sight of the fact that this is one component of the overall management of allergic patients. Many otolaryngologists provide care for allergic patients, and manage them in their office. This is being taught in residency programs as mandated by ACGME. SLIT is one new tool in the overall management of allergic rhinitis, and is best incorporated into your practice after you’ve spent some time learning specifically about it. That being said, it’s relatively straightforward and not overly difficult. Also, patients benefit from it.

Dr. Morris: The American Academy of Otolaryngic Allergy has a protocol and is teaching courses. Plus, courses are taught by private clinics and other associations. It shouldn’t be difficult to find training. The knowledge needed is quite similar to what you need to know for subcutaneous injection; it’s basically knowing how to mix up the treatment vials for the sublingual version.

How are patients selected for SLIT verses traditional IT?

Dr. Levine: Doctors should continue with the gold standard, which is injection therapy. At the same time, what I can tell you from my clinical experience of having done this now for about six years, is I think that this is an outstanding alternative for patients who would otherwise not want to go through injection immunotherapy. They can avoid the needles and the inconvenience of having to come into the office as much.