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Investigators found that when assessing patients with sickle cell disease and neuropathic pain the TRPV1 receptor is a crucial component in the development of hypersensitivity and potential therapeutic benefit of capsaicin.
According to new research, when assessing patients with sickle cell disease (SCD), the TRPV1 receptor is a crucial component in the development of hypersensitivity and potential therapeutic benefit of capsaicin.
There are variable clinical pain phenotypes associated with the rare disease, and evidence suggests neuropathic pain develops over time in these paitents. The complexity of this phenotype makes it difficult to treat and investigators noted that management methods lack substantial evidence.
In this study, patients with recurrent or chronic neuropathic pain were treated with a high dose of 8% topical capsaicin to evaluate the treatment's utility as a mechanistic probe and adjunctive pain therapy for sickle cell disease.
The investigators of the SPICE (Sickle Cell Pain: Intervention with Capsaicin Exposure) pilot study, led by Alexander K. Glaros, MD, Central Michigan University College of Medicine, was an open-label, single-arm safety investigation of off-label use of the medication, which is approved by the US Food and Drug Administration (FDA).
A total of 10 participants aged between 14-21 were recruited from the Comprehensive Sickle Cell Clinic at Children's Hospital of Michigan. Inclusion criteria required a sickle cell genotype of HbSS, HbSC, or HbSß0, and identifiable recurrent sites of pain where majority of prior acute pain episodes were localized, as well as a suggested neuropathic pain component.
Patients identified 2 of their most common areas of pain in order to identify localized sensitization for the assessment. The painDETECT questionnaire developed by Pfizer was completed at each of the 7 visits that took place at 6-week intervals.
Investigators utilized an electronic von Frey instrument to conduct mechanical quantitative sensory testing and determine a threshold for the localized pain in each patient's top 2 painful areas.
The primary endpoint of safety was met since there were no intervention-related serious adverse events. While all events were found to be unrelated to the intervention, there were 15 hospital admission due to vaso-occlusive pain episodes (VOEs) and an admission for delayed transfusion reaction during the study peiod.
One patient requested removal of the capsaicin patch at her second application during week 12 because of a burning sensation. Investigators reported mild erythema at the site of the patch with no other physical changes.
The rest of the patients found the patch to be tolerable, reporting a "warmth" or "burning" sensation and 7 of the 10 found immediate relief with the use of a cold pack during the first application. Most reported that the intensity of the sensation was much more mild at the following application.
By establishing the safety of this high dose capsaicin for patients with sickle cell disease it's now possible for the treatment to be considered as a probe of the pathophysiology of SCD-related chronic pain and a potential treatment, according to investigators.
"There were no severe treatment-related adverse events," investigators concluded. "Higher baseline pain sensitivity at a given body site was associated with self-reported history of more frequent localized vaso-occlusive pain episodes at that site. There was a statistically significant improvement in the mean Localized Peripheral Hypersensitivity Relief score (LPHR), evidencing TRPV1's importance to the development of hypersensitivity and a potential therapeutic benefit of capsaicin for SCD."
The study, "Targeting TRPV1 activity via high-dose capsaicin in patients with sickle cell disease" was published in eJHaem.