What the label lists and what reports show
Difelikefalin side effects
Difelikefalin's FDA label: “The most common adverse reactions (incidence ≥2% and ≥1% higher than placebo) were diarrhea, dizziness, nausea, gait disturbances, including falls, hyperkalemia, headache, somnolence, and mental status change.” FAERS holds 399 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 dizziness (45 reports).
- No generic listed
Check it at the source: the difelikefalin FDA label on DailyMed (effective August 26, 2025, Vifor (International), Inc.); the FDA FAERS public dashboard.
What does the label list?
From the label: adverse reactionsThe most common adverse reactions (incidence ≥2% and ≥1% higher than placebo) were diarrhea, dizziness, nausea, gait disturbances, including falls, hyperkalemia, headache, somnolence, and mental status change.
Table 2: Adverse Reactions in ≥ 2% of KORSUVA-Treated Subjects with Moderate-to-Severe CKD-aP Undergoing HD and ≥ 1% Higher Than Placebo in Trials 1 and 2
| Adverse Reactions | Placebo (N=424) n (%) | KORSUVA (N=424) n (%) |
|---|---|---|
| Diarrhea | 24 (5.7) | 38 (9.0) |
| Dizziness | 16 (3.8) | 29 (6.8) |
| Nausea | 19 (4.5) | 28 (6.6) |
| Gait Disturbances Gait disturbances includes: preferred terms of falls and gait… | 23 (5.4) | 28 (6.6) |
| Hyperkalemia | 15 (3.5) | 20 (4.7) |
| Headache | 11 (2.6) | 19 (4.5) |
| Somnolence | 10 (2.4) | 18 (4.2) |
| Mental Status Change Mental Status Change includes: preferred terms of confusional state… | 6 (1.4) | 14 (3.3) |
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: Dizziness, Somnolence, Mental Status Changes, and Gait Disturbances [see Warnings and Precautions (5.1) ] The most common adverse reactions (incidence ≥2% and ≥1% higher than placebo) were diarrhea, dizziness, nausea, gait disturbances, including falls, hyperkalemia, headache, somnolence, and mental status change. ( 6 ) To report SUSPECTED ADVERSE REACTIONS, contact Vifor (International) Inc. at 1-844-835-8277 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. A total of 1306 subjects undergoing HD who had moderate-to-severe pruritus were treated with KORSUVA in placebo-controlled and uncontrolled Phase 3 clinical trials. Of these, 711 were treated for at least 6 months and 400 were treated for at least one year. Two placebo-controlled Phase 3 trials (Trial 1 and Trial 2), in subjects undergoing HD who had moderate-to-severe pruritus were pooled to evaluate the safety of KORSUVA in comparison to placebo up to 12 weeks. …
Source: FDA drug label, Vifor (International), Inc., effective August 26, 2025 (SPL set 0c7b81f2-0fd3-47cb-8b0f-185e07f19c87), via openFDA; the full label on DailyMed
What do FAERS reports show?
399 reports list difelikefalin among the medicines taken, each a report of something that happened, not proof the medicine caused it; 62 are coded as a death and 120 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 21 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.
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?
- Difelikefalin: 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