BACKGROUND: Allergy immunotherapy can result in systemic allergic reactions and even life-threatening anaphylaxis requiring epinephrine administration. OBJECTIVE: The objective of this study was to describe epinephrine use in the clinical trial development programs of 3 rapidly dissolving sublingual immunotherapy tablets (SLITtablets; Merck & Co., Inc., Kenilworth, NJ/ALK, Horsholm, Denmark/Torii Pharmaceutical Co., Ltd., Tokyo, Japan). METHODS: Data on epinephrine use were collected from 13 timothy grass SLIT-tablet trials (MK-7243; <= 2800 bioequivalent allergen units/75,000 SQ-T dose, n =2497; placebo, n = 2139), 5 short ragweed SLIT-tablet trials (MK-3641; <= 12 Amb a 1-U, n =1725; placebo, n =770), and 11 house dust mite (HDM) SLIT-tablet trials (MK-8237; <= 12 SQ-HDM; n=3930; placebo, n =2246). RESULTS: In grass SLIT-tablet trials, epinephrine was used 13 times (grass SLIT-tablet, n =10; placebo, n =3). Eight administrations were for grass SLIT-tablet-related adverse events (AEs): 4 for systemic allergic reactions and 4 for local mouth and/or throat swelling. In ragweed SLIT-tablet trials, epinephrine was used 9 times in 8 subjects (ragweed SLIT-tablet, n =7; placebo, n =1 =2 administrations for protracted anaphylaxis]). Four administrations were for ragweed SLIT-tablet-related AEs: 1 for systemic allergic reaction and 3 for local mouth and/or pharynx/throat swelling. In HDM SLIT-tablet trials, epinephrine was administered 13 times (HDM SLIT-tablet, n =8; placebo, n =5). Four administrations were for HDM SLITtablet- related AEs: 1 for systemic allergic reaction and 3 for local events. Of the 16 epinephrine administrations for events related to SLIT-tablet treatment, 11 occurred within the first week of treatment (7 administrations on day 1) and 5 were subject self-administered. CONCLUSIONS: Epinephrine administrations in response to SLIT-tablet-related reactions in clinical trials are uncommon, typically occur within the first week of treatment, and are rarely self-administered. All SLIT-tablet-related events treated with epinephrine were nonserious. (C) 2016 American Academy of Allergy, Asthma & Immunology