What the label lists and what reports show
Trofinetide side effects
Trofinetide's FDA label: “The most common adverse reactions (that occurred in at least 10% of DAYBUE-treated patients and at least 2% greater than in placebo) were diarrhea and vomiting.” FAERS holds 6,691 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 diarrhoea (3,631 reports).
- No generic listed
Check it at the source: the trofinetide FDA label on DailyMed (effective September 4, 2026, Acadia Pharmaceuticals Inc.); 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 DAYBUE or DAYBUE STIX?DAYBUE or DAYBUE STIX may cause side effects, including: Diarrhea. Diarrhea is a common side effect of DAYBUE or DAYBUE STIX that can sometimes be severe. Diarrhea may cause you to lose too much water from your body (dehydration). Tell your healthcare provider if you have diarrhea while taking DAYBUE or DAYBUE STIX. Your healthcare provider may ask you to increase the amount you drink or take antidiarrheal medicine as needed. Weight loss. DAYBUE or DAYBUE STIX can cause weight loss. Tell your healthcare provider if you notice you are losing weight at any time during treatment with DAYBUE or DAYBUE STIX. Vomiting. Vomiting is a common side effect of DAYBUE or DAYBUE STIX. Sometimes vomit can get into your lungs (aspiration), which could cause an infection (aspiration pneumonia). Tell your healthcare provider if you have severe vomiting or if vomiting happens often. […]
Source: FDA drug label, Acadia Pharmaceuticals Inc., effective September 4, 2026 (SPL set 67e6f2d9-21f6-466f-9def-826c6a4b8257), via openFDA; the full label on DailyMed
What does the label list?
From the label: adverse reactionsThe most common adverse reactions (that occurred in at least 10% of DAYBUE-treated patients and at least 2% greater than in placebo) were diarrhea and vomiting.
Table 5 Adverse Reactions in at Least 5% of Patients Treated with DAYBUE and at Least 2% Greater than Placebo in Study 1
| Adverse Reaction | DAYBUE (N=93) % | Placebo (N=94) % |
|---|---|---|
| Diarrhea | 82 | 20 |
| Vomiting | 29 | 12 |
| Fever | 9 | 4 |
| Seizure | 9 | 6 |
| Anxiety | 8 | 1 |
| Decreased appetite | 8 | 2 |
| Fatigue | 8 | 2 |
| Nasopharyngitis | 5 | 1 |
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 labeling: Diarrhea [see Warnings and Precautions (5.1) ] Weight Loss [see Warnings and Precautions (5.2) ] Vomiting [see Warnings and Precautions (5.3) ] The most common adverse reactions (that occurred in at least 10% of DAYBUE-treated patients and at least 2% greater than in placebo) were diarrhea and vomiting. ( 6.1 ) To report SUSPECTED ADVERSE REACTIONS, contact Acadia Pharmaceuticals Inc. at 1-844-422-2342 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. In controlled and uncontrolled trials in patients with Rett syndrome, 260 patients ages 2 to 40 years were treated with DAYBUE, including 112 patients treated for more than 6 months, 92 patients treated for more than 1 year, and 44 patients treated for more than 2 years. The safety of DAYBUE STIX has been established from an adequate, well-controlled study, and open-label studies of DAYBUE [see Clinical Studies (14) ]. Below is a display of the adverse reactions of DAYBUE in these studies. …
Source: FDA drug label, Acadia Pharmaceuticals Inc., effective September 4, 2026 (SPL set 67e6f2d9-21f6-466f-9def-826c6a4b8257), via openFDA; the full label on DailyMed
What do FAERS reports show?
6,691 reports list trofinetide among the medicines taken, each a report of something that happened, not proof the medicine caused it; 39 are coded as a death and 802 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. Reports rose sharply in 2025 (2,524, against a median of 0 a year): FAERS counts follow reporting, which news, litigation and label changes can drive, not how often a reaction happens. Of the 18 reactions below, 7 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?
- Trofinetide: 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