Pruritus was exacerbated by sweating, heat, contact with any liquids on the skin, and sunburns, which doubled the intensity. The patient reported minimal, temporary relief with cannabidiol and cold fabric or air on his skin. His current regimen and nonpharmacologic efforts provided no relief and included oatmeal baths, cornstarch after showers, and patting instead of rubbing the skin with topical products. Trials with nonprescription diphenhydramine, loratadine, and calamine and zinc were not successful. He had not pursued phototherapy due to time limitations and travel constraints. He had a history of phlebotomies and hydroxyurea use, which he preferred to avoid and discontinued 1 year before presentation.
Despite improving hematocrit (< 45% goal) and platelet counts with ruxolitinib, the patient reported worsening pruritus that significantly impaired quality of life. His sleep and social and physical activities were hindered, preventing him from working. The patient’s active medications also included low-dose aspirin, sertraline, hydroxyzine, triamcinolone acetonide, and pregabalin for sciatica. Given persistent symptoms despite multimodal therapy and lifestyle modifications, the patient was started on naltrexone 25 mg daily, which provided immediate relief of symptoms. He continues to have adequate symptom control 2 years after naltrexone initiation.
Literature Review
A systematic search strategy was developed with the assistance of a medical librarian in Medline Ovid, using both Medical Subject Heading (MeSH) terms and synonymous keywords. The strategy was then translated to Embase, Web of Science, and Cochrane to extract publications investigating PV, pruritus, and/or naltrexone therapy. All searches were conducted on July 18, 2022, and the results of the literature review were as follows: 2 results from Medline Ovid; 34 results from Embase (2 were duplicates of Medline Ovid results); 3 results from Web of Science (all of which were duplicates of Medline Ovid or Embase results); and 0 results from Cochrane (Figure).
Discussion
Although pruritus is a common and often excruciating manifestation of PV, its pathophysiology remains unclear. Some patients with decreasing or newly normal hematocrit and hemoglobin levels have paradoxically experienced an intensification of their pruritus, which introduces erythropoietin signaling pathways as a potential mechanism of the symptom.8 However, iron replacement therapy for patients with exacerbated pruritus after phlebotomies has not demonstrated consistent relief of pruritus.8 Normalization of platelet levels also has not been historically associated with improvement of pruritus.8,9 It has been hypothesized that cells harboring Jak2 mutations at any stage of the hematopoietic pathway mature and accumulate to cause pruritus in PV.9 This theory has been foundational in the development of drugs with activity against cells expressing Jak2 mutations and interventions targeting histamine-releasing mast cells.9-11
The effective use of naltrexone in our patient suggests that histamine may not be the most effective or sole therapeutic target against pruritus in PV. Naltrexone targets opioid receptors in all layers of the epidermis, affecting cell adhesion and keratinocyte production, and exhibits anti-inflammatory effects through interactions with nonopioid receptors, including Toll-like receptor 4.12 The efficacy of oral naltrexone has been documented in patients with pruritus associated with immune checkpoint inhibitors, psoriasis, eczema, lichen simplex chronicus, prurigo nodularis, cholestasis, uremia, and multiple rheumatologic diseases.3,4,7-9,12-14 Opioid pathways also may be involved in peripheral and/or central processing of pruritus associated with PV.
Importantly, patients who are potential candidates for naltrexone therapy should be notified and advised of the risk of drug interactions with opioids, which could lead to symptoms of opioid withdrawal. Other common adverse effects of naltrexone include hepatotoxicity (especially in patients with a history of significant alcohol consumption), abdominal pain, nausea, arthralgias, myalgias, insomnia, headaches, fatigue, and anxiety.12 Therefore, it is integral to screen patients for opioid dependence and determine their baseline liver function. Patients should be monitored following naltrexone initiation to determine whether the drug is an appropriate and effective intervention against PV-associated pruritus.
CONCLUSIONS
This case study demonstrates that naltrexone may be a safe, effective, nonsedating, and cost-efficient oral alternative for refractory PV-associated pruritus. Future directions involve consideration of case series or randomized clinical trials investigating the efficacy of naltrexone in treating PV-associated pruritus. Further research is also warranted to better understand the pathophysiology of this symptom of PV to enhance and potentially expand medical management for patients.
Acknowledgments
The authors thank Amy Sisson (The Texas Medical Center Library) for her guidance and support in the literature review methodology.
