#297 Subcutaneous lignocaine for CKDaP in a haemodialysis patient—time to revisit an old remedy

Abstract Background and Aims Chronic kidney disease associated pruritus (CKDaP) affects around 60% of dialysis patients and can significantly impair sleep, mood, and quality of life. The pathophysiology of CKDaP is complex and incompletely understood, and is thought to involve non-histamine dependent pruritic pathways. Treatment options are limited. Method Case: A 65 year old woman with kidney failure from single kidney and diabetic kidney disease has been on haemodialysis (HD) for 4 years. Her long history of severe itch started 6 months prior to dialysis initiation, and the diagnosis of CKDaP was supported by dermatology assessment including skin biopsy. Biochemistry, apart from a short period of acute illness, has been consistently within target, with Ca <2.6 mmol/L, PO4 <2 mmol/L, and PTH <30 pmol/L during the 4 years. In addition to skin emollients, treatments sequentially included pregabalin up to a daily dose of 75 mg, Evening Primrose Oil oral capsules up to 2 daily, dialysis initiation with extended hours nocturnal HD to optimise clearance (>6 hours, Kt/V >2), oral cetirizine 10 mg daily, and topical compound ointment (menthol 5%, lignocaine 7%, and capsaicin 0.025%). Treatments had, at best, partial responses, and subsequent reescalation of symptoms occurred within weeks to months. Difelikefalin at 0.5 mcg/kg 3 times weekly post dialysis did result in dramatic improvement in itch, but 18 months later, itch had surged. Difelikefalin was increased to 1 mcg/kg, with a further 5 months of good symptom control. Results Thereafter, the patient developed an acute exacerbation of itch affecting her entire body, associated with severe sleep disturbance, ferocious scratching (Fig. 1), and emotional distress, despite continuing her existing treatments of emollients, pregabalin, difelikefalin 1 mcg/kg, and an empirical course of ivermectin (follow up of skin scraping for scabies were negative). Dermatology assessment confirmed CKDaP. She commenced continuous subcutaneous infusion (CSCI) of lignocaine at 200 mg over 24 hours, with up-titration to 600 mg CSCI over 24 hours. Itch had almost completely resolved by day 4, but rapid cessation of lignocaine at day 5 led to an acute surge in itch at day 9, and lignocaine was recommenced, with good result 48 hours later. At day 14, lignocaine was weaned and transitioned to ongoing oral mexiletine 150 mg twice daily. 4 months later, itch continued to be mild. Conclusion Case Discussion: CKDaP is a challenging condition to manage and severe cases can be extremely distressing for patients. Lignocaine blocks sodium channels in neuronal cell membranes and is widely and safely administered by CSCI in palliative care settings for pain relief. Its use is also described for intractable itch in T cell lymphoma, another condition associated with non-histamine-dependent pruritic pathways. Parenteral Iignocaine on haemodialysis has been tested and found efficacious as early as 1977 [1] but not routinely used, presumably due to monitoring, logistical, or safety concerns. The use of lignocaine as CSCI, and ongoing treatment with mexiletine, an oral medication with the same mechanism of action, may provide a therapeutic option for intractable CKDaP.