Difelikefalin Side Effects: What the Label and Studies Report

Difelikefalin is a prescription medicine. This page summarises what published product labeling and peer reviewed trials have reported about its adverse event profile. It does not describe how the medicine is given, and it does not evaluate whether any individual should receive it. This page is for educational purposes only and is not medical advice; consult a licensed physician about any symptom, medicine or treatment decision.

What Difelikefalin Is and Where It Is Approved

Difelikefalin is a synthetic peptide that acts as an agonist at kappa opioid receptors, and a 2022 drug monograph review described it as a peripherally restricted kappa opioid receptor agonist developed for pruritus associated with renal disease (PMID 36102903). A review of 2021 peptide and oligonucleotide approvals catalogued difelikefalin among the new peptide agents cleared in the United States that year (PMID 35215334).

At label level, the approved injection is indicated for moderate to severe pruritus associated with chronic kidney disease in adults undergoing hemodialysis. Reviews of symptom management in long term hemodialysis have discussed this indication and the place of difelikefalin among antipruritic options studied in that population (PMID 36726430). Any use outside an approved indication is investigational. Reviews of itch in other settings, including a 2024 overview of recently approved drugs and advanced clinical development programs in atopic dermatitis, illustrate that antipruritic candidates accumulate adverse event data in trials before any labeling applies to a given condition (PMID 38186219). Questions about whether a medicine applies to a particular situation belong with a prescribing clinician.

Boxed Warning Status

Published United States prescribing information for the approved difelikefalin injection does not carry a boxed warning. Because no boxed warning exists for that product, the label's safety content begins with warnings and precautions, followed by adverse reactions observed in clinical studies. The absence of a boxed warning is a regulatory fact about the document, not a statement about how any person will respond to the medicine.

Warnings and Precautions the Label Lists

The warnings and precautions section of the approved injection's labeling addresses central nervous system effects. The listed concerns are dizziness, somnolence, mental status change and gait disturbances including falls. The labeling also notes that the potential for these effects may be increased when the medicine is used together with centrally acting depressant medicines, sedating antihistamines or opioid analgesics. Anyone who experiences any of these effects, or who is uncertain how other medicines interact, is directed by the labeling to their prescriber rather than to self management.

Common Adverse Reactions: What Studies Report

The adverse reactions described for the approved injection come primarily from placebo controlled trials in adults receiving hemodialysis. A phase 3 trial published in 2020 randomly assigned hemodialysis patients with moderate to severe pruritus to intravenous difelikefalin at 0.5 micrograms per kilogram three times weekly or placebo for 12 weeks, and the researchers reported that diarrhea, dizziness and vomiting occurred more often in the difelikefalin group than in the placebo group (PMID 31702883). That study is the anchor trial most frequently summarised in later reviews of chronic kidney disease associated pruritus (PMID 40724504).

Grouped by Body System

Frequency figures in labeling are drawn from the pooled placebo controlled trial program and are expressed as the proportion of treated participants in whom an event occurred at a rate at or above a stated threshold and above placebo. Individual trial publications report their own counts, and the specific percentages differ between documents because the populations, durations and definitions differ.

Phase 3 Evidence in Hemodialysis Populations: What Studies Report

The 2020 phase 3 trial enrolled adults receiving hemodialysis who had moderate to severe pruritus, used a 12 week double blind period and measured itch intensity on a numerical rating scale, with the researchers reporting a greater reduction in itch intensity with difelikefalin than with placebo alongside the adverse events noted above (PMID 31702883). Reviews of uremic pruritus published since then have described that trial as the principal controlled evidence underpinning the approved indication and have summarised its tolerability findings for clinicians managing dialysis patients (PMID 40724504).

Separate randomized work has been conducted in Japan. A randomized clinical trial published in 2022 evaluated efficacy and safety of difelikefalin in Japanese patients with moderate to severe pruritus receiving hemodialysis (PMID 35511180). A further randomized evaluation of difelikefalin in hemodialysis patients in Japan was published in 2023 (PMID 38320524). Regional trials matter for adverse event interpretation because background medicine use, dialysis practice and body weight distributions differ between study populations, a point reflected in reviews of dialysis associated itch (PMID 33707097).

Pooled and Review Evidence: What Studies Report

A 2024 systematic review and meta analysis pooled randomized controlled trials of difelikefalin for pruritus in hemodialysis patients and assessed both efficacy and safety outcomes across those trials (PMID 39091079). Pooled analyses combine events that individual trials may record too rarely to interpret, but they also inherit the limits of the trials they contain, including short double blind periods and selected populations.

Broader reviews of antipruritic drug evidence place these findings in context. A 2023 Cochrane review of pharmacological interventions for pruritus in adult palliative care patients examined trials of multiple drug classes and graded the certainty of the available evidence (PMID 37314034). Nephrology reviews of pruritus in dialysis patients have likewise described the range of treatments studied for uremic itch and the methodological limits of much of that literature (PMID 36153894).

Drug Interactions and Special Populations at Label Level

The approved injection's labeling describes the potential for additive central nervous system effects when the medicine is combined with centrally acting depressants, sedating antihistamines or opioid analgesics. Labeling also contains sections on use in pregnancy and lactation and on pediatric use, where data are limited or absent. These are label level statements; how they apply to any individual, including people taking several medicines or people with additional conditions, is a matter for the prescribing clinician.

What the Published Record Does Not Settle

• Duration. The pivotal double blind period in the 2020 phase 3 trial lasted 12 weeks, so controlled adverse event data beyond that window are limited in that study (PMID 31702883).
• Population. Controlled trial data come from adults receiving hemodialysis, and reviews of chronic kidney disease associated pruritus emphasise that this group carries a heavy comorbidity and medicine burden that complicates attribution of any single event (PMID 36726430).
• Rare events. Randomized trials of this size detect common events reliably and uncommon events poorly, a general limitation that applies to the pooled dataset as well (PMID 39091079).
• Other itch conditions. Adverse event data generated in dialysis populations do not transfer automatically to investigational settings in other pruritic diseases, where separate development programs are described in the dermatology literature (PMID 38186219).

Questions That Belong With a Prescriber

Symptoms such as new or worsening dizziness, drowsiness, confusion, unsteadiness on walking, falls, persistent diarrhea or vomiting, and laboratory abnormalities such as elevated potassium are matters for the prescribing clinician and the dialysis care team, not for self assessment against a web page. Medicine lists, including over the counter sedating antihistamines, are relevant to that conversation because the labeling flags additive central nervous system effects. Nothing on this page constitutes a recommendation to start, stop, continue or change any treatment.

References

• A Phase 3 Trial of Difelikefalin in Hemodialysis Patients with Pruritus (The New England Journal of Medicine, 2020)
• The efficacy and safety of difelikefalin for pruritus in hemodialysis patients: a systematic review and meta-analysis of randomized controlled trials (Renal Failure, 2024)
• Efficacy and Safety of Difelikefalin in Japanese Patients With Moderate to Severe Pruritus Receiving Hemodialysis: A Randomized Clinical Trial (JAMA Network Open, 2022)
• Difelikefalin for Hemodialysis Patients with Pruritus in Japan (NEJM Evidence, 2023)
• Difelikefalin for pruritus associated with renal disease (Drugs of Today, 2022)
• 2021 FDA TIDES (Peptides and Oligonucleotides) Harvest (Pharmaceuticals, 2022)
• Pruritus in Uremic Patients: Approaches to Alleviating a Common Symptom in Chronic Kidney Disease (Life, 2025)
• Alleviating symptoms in patients undergoing long-term hemodialysis: a focus on chronic kidney disease-associated pruritus (Clinical Kidney Journal, 2023)
• Pruritus in dialysis patients. Review and new perspectives (Nefrologia, 2022)
• Pruritus in dialysis patients. Review and new perspectives (Nefrologia, 2021)
• Pharmacological interventions for pruritus in adult palliative care patients (Cochrane Database of Systematic Reviews, 2023)
• Treatment of atopic dermatitis: Recently approved drugs and advanced clinical development programs (Allergy, 2024)