What the label lists and what reports show
Voxelotor side effects
Voxelotor's FDA label: “Most common adverse reactions (incidence ≥10% with a difference of >3% compared to placebo) are headache, diarrhea, abdominal pain, nausea, rash, and pyrexia.” FAERS holds 22,300 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 sickle cell anaemia with crisis (11,218 reports).
- No generic listed
Check it at the source: the voxelotor FDA label on DailyMed (effective December 26, 2023, Global Blood Therapeutics, Inc, A subsidiary of Pfizer 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 OXBRYTA?OXBRYTA can cause serious side effects, including: • Severe skin rash and serious allergic reactions. Treatment with OXBRYTA may cause severe skin reactions and serious allergic reactions. The organs in your body may also be affected, such as your liver, kidneys or lungs, and your blood cells. […]
Source: FDA drug label, Global Blood Therapeutics, Inc, A subsidiary of Pfizer Inc., effective December 26, 2023 (SPL set 3c557fac-29ec-483f-b691-8a935d4decc3), via openFDA; the full label on DailyMed
What does the label list?
From the label: adverse reactionsMost common adverse reactions (incidence ≥10% with a difference of >3% compared to placebo) are headache, diarrhea, abdominal pain, nausea, rash, and pyrexia.
Table 4: Adverse Reactions (≥10%) in Patients Receiving OXBRYTA with a Difference Between Arms of >3% Compared to Placebo in HOPE
| Reaction | OXBRYTA 1,500 mg (N=88) | Placebo (N=91) |
|---|---|---|
| Headache | 32% | 25% |
| Diarrhea | 23% | 11% |
| Abdominal Pain Abdominal pain (grouped PTs) includes the following PTs: abdominal pain,… | 23% | 16% |
| Nausea | 19% | 10% |
| Rash Rash (grouped PTs) includes the following PTs: rash, urticaria, generalized rash,… | 15% | 11% |
| Pyrexia | 15% | 8% |
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 reaction is discussed in other sections of the labeling: • Hypersensitivity Reactions [see Contraindications (4) and Warnings and Precautions (5.1) ]. Most common adverse reactions (incidence ≥10% with a difference of >3% compared to placebo) are headache, diarrhea, abdominal pain, nausea, rash, and pyrexia. ( 6.1 ) Most common adverse reactions (incidence >10%) reported in pediatric patients 4 to <12 years are pyrexia, vomiting, rash, abdominal pain, diarrhea, and headache. ( 6.1 ) To report SUSPECTED ADVERSE REACTIONS, contact Pfizer Inc. at 1-800-438-1985 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. Adults and Pediatric Patients 12 Years and Older The safety of OXBRYTA was evaluated in the HOPE trial based on data from 88 patients with SCD who received OXBRYTA 1,500 mg and 91 patients who received placebo orally once daily [see Clinical Studies (14.1) ]. Seventy-four patients received OXBRYTA 1,500 mg once daily for ≥24 weeks, 65 patients for ≥48 weeks, and 63 patients completed the 72-week treatment period. …
Source: FDA drug label, Global Blood Therapeutics, Inc, A subsidiary of Pfizer Inc., effective December 26, 2023 (SPL set 3c557fac-29ec-483f-b691-8a935d4decc3), via openFDA; the full label on DailyMed
What do FAERS reports show?
22,300 reports list voxelotor among the medicines taken, each a report of something that happened, not proof the medicine caused it; 416 are coded as a death and 7,858 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 2022 (9,276, against a median of 141 a year): FAERS counts follow reporting, which news, litigation and label changes can drive, not how often a reaction happens. Of the 19 reactions below, 8 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?
- Voxelotor: 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