Efficacy and safety of pregabalin versus gabapentin among chronic pruritus patients: a randomized study

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Abstract

Chronic pruritus (CP), a persistent itching sensation lasting over 6 weeks, significantly impacts physical, psychological, and social well-being, causing disrupted sleep, anxiety, reduced attention span, and impaired sexual function. CP is common in the elderly and can arise from skin issues or systemic conditions, with 8–15% of cases having unknown etiology. As a result of varied causes and patient factors, general therapeutic recommendations for CP are challenging. Gabapentin and pregabalin, the γ-Aminobutyric acid molecules, are preferred when conventional treatments fail. Despite limited research on CP of various causes, no trials have directly compared pregabalin and gabapentin for CP, prompting this study. This randomized, open-label clinical trial was conducted in an outpatient setting at a tertiary healthcare facility in India. Patients with pruritus for more than 6 weeks, aged over 18 years were included. Patients with pruritus of known dermatological etiology, pregnant and lactating women, patients with aspartate and alanine transaminases raised three times above the upper normal level, creatinine clearance ≤30 mL/min, and those on therapeutic opioids were excluded. The primary objective was to evaluate the efficacy of pregabalin versus gabapentin using the Visual Analogue Scale (VAS) after 6 weeks of therapy. Secondary objectives included comparing efficacy using the 5D pruritus scale1 and Dermatology Life Quality Index (DLQI) score2 and comparing the safety profiles of the study drugs. Patients were randomized at a 1:1 ratio using block randomization with a block size of 4 into the pregabalin or gabapentin groups using concealed allocation. Pregabalin 150 mg or gabapentin 600 mg were given twice daily in two divided doses after food for 6 weeks. Patients were followed up at Week 2 for safety evaluation and Week 6 for efficacy and safety evaluation at hospital visits. The sample size was calculated using Aquino et al.3 data, assuming a standard deviation (SD) of 2 in the study group and 1.9 in the control group, an effect size of 1.02, and a clinically meaningful mean difference of 2 using a VAS score, with 90% power, 5% alpha error, and 10% dropout rate, resulting in 46 patients. Data were analyzed using SPSS v.24. The intention-to-treat approach was followed to analyze efficacy data, and missing data were imputed. P-value < 0.05 was considered statistically significant. A total of 46 patients were recruited from 78 individuals screened from October 2022 to September 2023 (Fig. 1). Baseline variables were comparable between groups. The average age in the pregabalin and gabapentin groups was 52 and 55 years, respectively. CP improved significantly as per VAS at Week 6 (P = 0.001) and change in the VAS from baseline to Week 6 in the pregabalin group compared to the gabapentin group. Meanwhile, both groups showed significant improvement from baseline to Week 6 individually per the VAS. Significant improvement at Week 6 in the pregabalin group was evident using the 5D pruritus scale and DLQI compared to the gabapentin group. Also, statistically significant improvement of pruritus using the 5D pruritus scale and DLQI within the individual groups from baseline to Week 6 was found. Adverse events, primarily dizziness, were mild to moderate and comparable between groups (Table 1). No severe or serious adverse events were reported. Previous trials comparing pregabalin and gabapentin yielded diverse outcomes. Khan et al. found pregabalin more efficacious for uremic pruritus (UP),4 while Ravindran et al. reported no significant difference between pregabalin and gabapentin in UP.5 Our study expands on prior findings, encompassing a broader population of patients with CP beyond UP. The better efficacy of pregabalin may be attributed to its advantageous linear absorption and higher bioavailability than gabapentin. We excluded CP of dermatologic origin, as it often necessitates specific treatments. Future research should explore long-term effects and conduct health economic analyses for cost-effectiveness. In conclusion, pregabalin significantly improved CP unresponsive to conventional treatments compared to gabapentin, with both drugs being safe and tolerable. The authors obtained consent for the publication of recognizable patient photographs or other identifiable material and included it at the time of article submission to the journal, stating that all patients gave consent with the understanding that this information may be publicly available. India (CTRI) registration number: CTRI/2022/09/058360.

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