Difelikefalin, sold under the brand name Korsuva, is an analgesic opioid peptide used for the treatment of moderate to severe itching. It acts as a peripherally specific, highly selective agonist of the κ-opioid receptor (KOR).Difelikefalin was approved for medical use in the United States in August 2021.Difelikefalin acts as an analgesic by activating KORs on peripheral nerve terminals and KORs expressed by certain immune system cells. Activation of KORs on peripheral nerve terminals results in the inhibition of ion channels responsible for afferent nerve activity, causing reduced transmission of pain signals, while activation of KORs expressed by immune system cells results in reduced release of proinflammatory, nerve-sensitizing mediators (e.g., prostaglandins). Society and culture
Legal status
On 24 February 2022, the Committee for Medicinal Products for Human Use (CHMP) of the European Medicines Agency adopted a positive opinion, recommending the granting of a marketing authorization for the medicinal product Kapruvia, intended for treatment of moderate-to-severe pruritus associated with chronic kidney disease. The applicant for this medicinal product is Vifor Fresenius Medical Care Renal Pharma France. Difelikefalin was approved for medical use in the European Union in April 2022. Research
It is under development by Cara Therapeutics as an intravenous agent for the treatment of postoperative pain. An oral formulation has also been developed. Due to its peripheral selectivity, difelikefalin lacks the central side effects like sedation, dysphoria, and hallucinations of previous KOR-acting analgesics such as pentazocine and phenazocine. In addition to use as an analgesic, difelikefalin is also being investigated for the treatment of pruritus (itching).
A rash is a change of the human skin which affects its color, appearance, or texture. A rash may be localized in one part of the body, or affect all the skin. Rashes may cause the skin to change color, itch, become warm, bumpy, chapped, dry, cracked or blistered, swell, and may be painful. The causes, and therefore treatments for rashes, vary widely. Diagnosis must take into account such things as the appearance of the rash, other symptoms, what the patient may have been exposed to, occupation, and occurrence in family members. The diagnosis may confirm any number of conditions. The presence of a rash may aid diagnosis; associated signs and symptoms are diagnostic of certain diseases. For example, the rash in measles is an erythematous, morbilliform, maculopapular rash that begins a few days after the fever starts. It classically starts at the head, and spreads downwards. Differential diagnosis
Common causes of rashes include:

Food allergy
Medication side effects
Anxiety
Allergies, for example to food, dyes, medicines, insect stings, metals such as zinc or nickel; such rashes are often called hives. Skin contact with an irritant
Fungal infection, such as ringworm
Balsam of Peru
Reaction to vaccination
Skin diseases such as eczema or acne
Exposure to sun (sunburn) or heat
Friction due to chafing of the skin
Irritation such as caused by abrasives impregnated in clothing rubbing the skin.