What the label lists and what reports show
Ensifentrine side effects
Ensifentrine's FDA label: “Most common adverse reactions (incidence greater and equal to 1% and more common than placebo) include back pain, hypertension, urinary tract infection, and diarrhea.” FAERS holds 1,505 reports naming it through July 30, 2026; the reaction reported most often, leaving out the conditions it is used for, product-use terms and outcomes, is dyspnoea (323 reports).
- No generic listed
Check it at the source: the ensifentrine FDA label on DailyMed (effective April 23, 2026, MERCK SHARP & DOHME LLC); the FDA FAERS public dashboard.
What does the patient leaflet say about side effects?
From the patient leaflet: What are the possible side effects of OHTUVAYRE?OHTUVAYRE can cause serious side effects, including: Sudden breathing problems immediately after inhaling your medicine. If you have sudden breathing problems immediately after inhaling your medicine, stop using OHTUVAYRE and call your healthcare provider right away or go to the nearest hospital emergency room right away. Mental health problems including suicidal thoughts and behavior. You may experience mood or behavior changes when taking OHTUVAYRE. […]
Source: FDA drug label, NDA217389 (Msd), as published by MERCK SHARP & DOHME LLC, effective April 23, 2026 (SPL set e6433c98-41a0-4f99-8f7f-d0e9db6e3f40), via openFDA; the full label on DailyMed
What does the label list?
From the label: adverse reactionsMost common adverse reactions (incidence greater and equal to 1% and more common than placebo) include back pain, hypertension, urinary tract infection, and diarrhea.
Table 1. Adverse Reactions with OHTUVAYRE with incidence ≥ 1% and More Common than Placebo in Patients with COPD in the Pooled 24-Week Safety Population (ENHANCE-1 and ENHANCE-2)
| Adverse Reaction | OHTUVAYRE N=975 n (%) | Placebo N=574 n (%) |
|---|---|---|
| Back pain | 18 (1.8%) | 6 (1.0%) |
| Hypertension | 17 (1.7%) | 5 (0.9%) |
| Urinary tract infection | 13 (1.3%) | 6 (1.0%) |
| Diarrhea | 10 (1.0%) | 4 (0.7%) |
Rows and numbers as the label prints them, under its own column headings (the first rows of a longer table where it runs on). A reaction in a trial table is not necessarily caused by the medicine, and trials differ from everyday use.
From the label: adverse reactions, continuedThe following clinically significant adverse reactions are described elsewhere in the labeling: Paradoxical Bronchospasm [see Warnings and Precautions (5.2) ] Psychiatric Events Including Suicidality [see Warnings and Precautions (5.3) ] Most common adverse reactions (incidence greater and equal to 1% and more common than placebo) include back pain, hypertension, urinary tract infection, and diarrhea. ( 6.1 ) To report SUSPECTED ADVERSE REACTIONS, contact Merck Sharp & Dohme LLC at 1-800-672-6372 or FDA at 1-800-FDA-1088 or www.fda.gov/medwatch. 6.1 Clinical Trials Experience Because clinical trials are conducted under widely varying conditions, adverse reaction rates observed in the clinical trials of a drug cannot be directly compared to rates in the clinical trials of another drug and may not reflect the rates observed in practice. The safety of OHTUVAYRE was based on the pooled safety population from two randomized, double-blind, placebo-controlled trials (ENHANCE-1 and ENHANCE-2) for 24 weeks, and a 48-week cohort that assessed safety in ENHANCE-1. In these trials, a total of 975 patients received 3 mg of OHTUVAYRE twice daily administered by oral inhalation using a standard jet nebulizer [see Clinical Studies (14) ]. The safety population included all patients who were randomized and received at least one dose of OHTUVAYRE or placebo. …
Source: FDA drug label, NDA217389 (Msd), as published by MERCK SHARP & DOHME LLC, effective April 23, 2026 (SPL set e6433c98-41a0-4f99-8f7f-d0e9db6e3f40), via openFDA; the full label on DailyMed
What do FAERS reports show?
1,505 reports list ensifentrine among the medicines taken, each a report of something that happened, not proof the medicine caused it; 61 are coded as a death and 294 as a hospital stay. Counts follow how widely a medicine is used and watched, and they are not a measure of how risky it is. Of the 18 reactions below, 5 are named by the same term (in US spelling) in the label's adverse reactions, warnings or patient leaflet; a reaction the label does not name may still be there under another word, and a report does not show that the medicine caused it.
Reports received each year
The 25 most reported reactions
Source: FDA Adverse Event Reporting System (FAERS) via openFDA, reports through July 30, 2026; reactions as MedDRA preferred terms
What next?
- Ensifentrine: the full record
- label, generics, price, shortages, recalls
- Report a side effect to the FDA
- MedWatch
- Side effects hub
- the most reported medicines and reactions