While the FDA has not yet approved SLIT because the effectiveness and safety are not well known, some physicians are prescribing the treatment to patients.
Weily Soong, MD, of Alabama Allergy & Asthma Center, says because allergy injections have been used for so long, physicians have a better understanding about the immunological mechanisms involved and know how the shots can cause changes in a person's immune system. "We have also learned what doses are needed for the shots to be effective and to create a long-term tolerance in patients lasting for 10 years or more," he says.
Soong says that the discussion of using SLIT instead of traditional injections is one that comes up from time to time. "It has come up again and there are a number of physicians who are not board-certified allergists starting to prescribe these drops," he says.
James Bonner, MD, who practices with Soong, says developers of SLIT are making progress in establishing appropriate dosing and developing safe regimens of administration. "While the therapy is not yet FDA approved, it is something physicians and patients can look forward to," he says.
Proponents of SLIT like the treatment because it can be administered without an injection and can be taken at home. Shots must be administered in a physician's office. For children, there is no pain because there is no injection.
While Soong agrees these may be favorable reasons for using SLIT, he is concerned with the research that has been done for the treatment. "Developers of SLIT medicines quote European studies in their marketing materials. The problem with that is European studies use drops that are 100 to 1,000 times stronger than what is available in the United States. The extracts here are not the same strength," he says. "I've always felt that before you do something, you need to know how and why it works and the immunology behind it. We do not yet know the optimal dose for the allergy extracts in SLIT. It also appears that SLIT is less effective in the long-term than allergy injections.”
In addition to not being approved by the FDA, SLIT therapies have not been approved by the American College of Allergy and Immunology or the American Academy of Allergy, Asthma and Immunology, says Joe LaRussa, MD, of Pediatric and Adult Asthma and Allergy. "There is not one board certified allergist in the state of Alabama using these drops," he says.
Because SLIT is not FDA approved, insurance companies do not cover it. "Blue Cross says the treatment is experimental, so people are paying physicians in cash to receive it," Soong says.
LaRussa says the medicines that have been developed thus far for SLIT therapy target only one allergen per drop or pill whereas injections can combine medicines for multiple allergies, which most people require. "A lot of people are allergic to grass, so a pill or drop for that particular allergen might be effective. But most people are not allergic to just one thing, so when you start combining therapies for all allergens in this treatment, will it be safe and effective or not?" he says. "Frequently, people ask me what I would do if it were my child. I currently have my child on allergy shots."
Bonner thinks the initial benefits of SLIT will largely be for patients who are allergic to relatively few substances. Developers may provide a way to immunize people with multiple allergies in the future, but he also is concerned about risk and effectiveness as well as cost for these new therapies. "None of these treatments is without risk,” he says. “The shots we give have enough risk associated with them that we always give them in the allergist's office. Tablets are given under the tongue daily, so a patient gets 50 times the total dose per month that they get with an injection. How costly will that be? What are the risks? I guess it will depend on how the pharmaceutical companies develop them."
The fact that each tablet currently is effective only for one allergen also may have cost and safety implications. "If a person has allergies to multiple things, will they have to use eight tablets under the tongue every day? Ways to combine treatment for multiple sensitivities are likely to be found, but again, cost may be an issue," Bonner says.
In the long run, Bonner says, competition between SLIT and allergy shots will depend on an individual's specific needs and preferences for how he wants to be treated. "As advances are made in SLIT, they wilI occur in parallel with advances in subcutaneous immunotherapy that will make extracts more potent and, at the same time, safer with therapeutic benefit requiring relatively few injections," he says. "I think SLIT will be a positive thing once it is developed effectively and safely. Currently, there are some disadvantages, but with more research and interest, I hope some of those disadvantages will disappear."