Subcutaneous allergen immunotherapy (SCIT) vs Sublingual immunotherapy (SLIT)
Subcutaneous allergen immunotherapy (SCIT), or “allergy shot therapy,” has been around since the early 1900s. It is considered a well-accepted therapy for allergic rhinitis and asthma. Sublingual immunotherapy (SLIT) has garnered a great deal of attention lately since two sublingual tablet formulations to treat grass allergy were reviewed by an FDA advisory committee. The advisory committee recommended approval of Oralair™ and Grastek™ tablets, which are meant to treat grass pollen allergy symptoms. Although the FDA is not bound by the committee’s guidance, typically approval of the products follows soon afterwards.
While we at the Asthma & Allergy Associates of Florida are always excited about new therapies for allergic disease, we are concerned about what is starting to unfold in the medical community. It is clear that these pharmaceutical company manufactured sublingual tablets are effective, but it is not at all certain that compounded sublingual or under-the-tongue “allergy drops” (liquid treatments made up from allergen extracts that are only approved for injection therapy) will benefit patients. We fear that these drops will gain popularity in that they will be offered as treatment for a larger variety of allergens versus conventional injection therapy. Patients may ask, “Why should I only get treated for grass allergy, when I am allergic to so many things such as dust mite, animal dander, and mold?” There are two main issues regarding sublingual therapy. First, the “devil is in the dosing.” Secondly, there is no good data supporting sublingual therapy for more than one allergen at a time. Thirdly, the delivery system, a tablet versus a liquid, can make a big difference in effectiveness.
Subcutaneous immunotherapy (SCIT), or injection therapy, has been shown in several studies to be a very cost-effective option for treating allergic rhinitis and asthma. It may be a different story for sublingual therapy (SLIT).
Sublingual immunotherapy (SLIT), “Allergy Drops”
As far as the dosing, the most conservative estimates are that the dose needed for effective SLIT is 30 times more than that needed for injection therapy. This can lead to a very high cost to treat a patient effectively. While the raw extract cost for injection therapy may only be a few dollars a month (the majority of the cost being due to the need for administrative staff, nurses, and supervision by the physician), the extract costs for sublingual therapy will end up being extremely high when more one or two allergens is being treated. A ballpark estimate, based on controlled studies of sublingual therapy, would be that the cost of extract alone in treating year-round allergens such as dust mite, cat and dog allergy would be $50-$100 for each allergen. Treating pollens would be slightly less per allergen. The consequence is that the extract costs would be prohibitive for most American patients who are usually allergic to multiple allergens. To this point, in Europe, where sublingual therapy is most popular, patients are typically treated for one allergen. Another hint as to the potential the high cost of this therapy is that the estimate for the cost upcoming grass tablets will be approximately $150 per month, and this is only to treat one allergen.
As far as the second point, there is really no good data to support treating more than one allergen at a time with sublingual therapy, as very few studies have been done. Lastly, as was mentioned above, there may be differences in effectiveness when the allergen is given in different formats (tablet vs liquid). The products on the horizon to be approved in the United States are mostly tablets.
Also concerning to us are claims that sublingual therapy is more effective than injection therapy for allergies. There is absolutely no basis in fact for this. There are some studies showing similar benefit, but the majority of the evidence suggests a greater benefit with injection therapy.
There is no question that the idea of sublingual therapy allergy is an attractive one. Because of the lower incidence of allergic reactions with sublingual therapy, patients would be able to treat themselves at home as opposed to getting therapy in a doctor’s office. Also, because of the lower chance of reactions, very young children can be treated. Plus, no needles are involved.
In summary, the question is not whether sublingual allergen immunotherapy works (it apparently does), it is whether physicians are going to use adequate doses in the proper format. For unclear reasons, allergic individuals in the US tend to be allergic to multiple allergens. This results in sublingual therapy being an expensive proposition.
We foresee that SLIT will have a place in certain situations (small children, patients allergic to one or two allergens, moderate to severe asthmatics). Asthma and Allergy Associates of Florida is in the process of deciding the best situations in which to use this type of therapy. We strongly suggest to the public that the be very aware of the limitations of sublingual therapy. For example, we would advise any patient being offered this therapy to specifically ask their physician whether they will be receiving an adequate dose of each allergen.
There is an detailed and referenced review of this topic at the following address: http://www.asthmacenter.com/index.php/News/details/sublingual_immunotherapy/