My twitter feed and news subscriptions are all buzzing about the latest publication on sublingual immunotherapy, an alternative to conventional allergy shots. The Journal of the American Medical Association (JAMA) published a review this week titled Sublingual Immunotherapy for the Treatment of Allergic Rhinoconjunctivitis and Asthma. This publication looks at the effectiveness of sublingual drops for nasal allergies and asthma.
What is immunotherapy?
When it comes to immunotherapy and allergies we classify the way it is administered into two categories: 1) subcutaneous (shots) and 2) sublingual (drops under the tongue). The idea is that exposures through the nose, lungs and eyes are generally the cause of allergies. Exposing the body through the gut (drops) or directly into the body (shots) are routes that tend to promote tolerance.
Sixty-three studies were examined; almost all of the studies took place in Europe. The article indicates in eight of 13 studies, 40% showed improvement in asthma symptoms versus its comparator (which included placebo, medications and other sublingual treatments) and nine of 36 rhinitis studies showed a greater than 40% improvement verses its comparator. Medication use was reduced by 40% in 16 of 41 studies.
There is a tremendous amount of interest in allergy drops, and for good reason. But there are a few unanswered questions board-certified allergists should consider before adopting widespread use.
1) When will allergens be made specifically for sublingual use in the United States? In the United States, there is not an FDA-approved formulation for sublingual use. If providers are using allergen for sublingual use, there is a good chance they are using allergens manufactured for injection purposes “off-label.”
2) What is the optimum dosing schedule and strength? There is a broad range of strengths and dosing schedules in the European articles published: from once a week to several times a day. Doctors using drops in the U.S. are using their best estimate as to what would be an effective dose.
3) What is the duration of therapy? Should it be continuous or could it be administered before a season or exposure? We know allergy shots should be continued for three to five years to achieve a prolonged, if not life-long benefit. The best duration for sublingual therapy is yet to be determined. Studies range from several years to using just prior to a particular season. Again, in the United States, until more studies define the best duration, it’s a doctor’s best guess at duration of therapy.
4) Can multiple allergens be mixed in one vial? It is common in the United States to use multiple allergens in someone’s allergy shots. Dr. Harold Nelson, often revered as the ultimate source of knowledge when it comes to immunotherapy in the United States, points out in his editorial of the article that only one of the double-blind, placebo-controlled trials used more than one allergen at a time.
5) How does it compare to conventional allergy shots? That question remains unanswered. Data does not exist directly comparing long-term outcomes for each treatment. I think most board-certified allergists would assert that conventional shots are currently more effective, based on what we know, for most people with longer durations of benefit. But this could change as research in the United States grows.
Advantages and Disadvantages
The most attractive features of sublingual therapy will likely be safety (reduced anaphylaxis risk compared to shots) and convenience. Who wants to make several trips to the doctor over several years if sublingual therapy is shown to be as effective?
The disadvantages are a lack of answers to the questions above and the cost. It is generally not covered by insurance since there is no FDA-approved formulation in the United States. Oral irritation appears to be a common side effect. Access can also be an issue. Given the unanswered questions, many board-certified allergists are not yet prescribing. Look for that to change as more studies are published.
The point of my article is to promote what is still unknown about sublingual immunotherapy. Ask a lot of questions. Take into account your specific situation and needs, weighing the benefit and risks of all available therapies. Be an informed patient before pulling out your wallet to pay for out-of-pocket therapy that still does not have an FDA-approved formulation in the United States.
Disclaimer: This blog is not intended to create a doctor-patient relationship with any reader. If you need personalized medical advice, contact your primary care physician or other physician in your community.