Real-world Experience with Once-daily Gabapentin for the Treatment of Postherpetic Neuralgia (PHN)

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SCIENCE
Real-world Experience with Once-daily Gabapentin for the Treatment of Postherpetic Neuralgia (PHN)
Key Take-Away: 

To best reflect the real-world population of patients with postherpetic neuralgia (PHN), a novel approach of gastroretentive gabapentin has significantly reduced the average pain score as early as possible.

The persistence of pain for 3 or more months after the resolution of acute herpes zoster is known as postherpetic neuralgia (PHN). Gabapentin has been known to reduce the pain and also acts a first-line treatment for PHN. However, its potential effects are limited due to its intrinsic properties, including a short half-life of 5-7 hours and its uptake by a saturable uptake transporter, which require immediate-release of gabapentin to be taken at least 3 times a day.

ABSTRACT: 
Background: 

The persistence of pain for 3 or more months after the resolution of acute herpes zoster is known as postherpetic neuralgia (PHN). Gabapentin has been known to reduce the pain and also acts a first-line treatment for PHN. However, its potential effects are limited due to its intrinsic properties, including a short half-life of 5-7 hours and its uptake by a saturable uptake transporter, which require immediate-release of gabapentin to be taken at least 3 times a day.

Application of a novel gastroretentive technology to gabapentin to improve its pharmacokinetics led to a formulation that can be administered once daily. Gastroretentive gabapentin (G-GR) significantly reduced the average pain score as early as day 2, which continued to decrease over the time.

  • Rationale behind research
  1. As clinical trials do not always accurately reflect the efficacy and safety of a drug in real world clinical practice. Therefore, this study was designed to evaluate the potential benefits of once-daily gabapentin for the treatment of PHN.
  • Objective

To evaluate the safety and effectiveness of once-daily Gastroretentive gabapentin (G-GR) for the treatment of postherpetic neuralgia in real-world clinical practice

 

Methods: 

 

Study outcomes

o   Primary outcome: Visual analogue scale (VAS) score from baseline to the end of the study

o   Secondary outcomes:

  • Percent change in the VAS score baseline to week 2 and week 8
  • Proportion of patients with ≥ 30%, ≥ 50%, ≥ 20 mm reduction from baseline in VAS score at week 2 and week 8
  • Proportion of patients who were “much” or “very much” improved on the Patient Global Impression of Change (PGIC) and Clinical Global Impression of Change (CGIC) instruments at week 8

Time-points

o   Efficacy: Baseline and daily up to 8 weeks

Results: 

 

Baseline: The mean age of patients in the efficacy population was 67.4 (12.8) years and 92.4% had a VAS score of > 20 mm, 28.9% primarily opioids and 13.2% anticonvulsants

  • Primary outcomes:
  • The mean change from baseline to week 2 in VAS score was 16.0 mm with a mean percent change from baseline of 26.5% and 20.9 mm from baseline to week 8 with a mean percent change of 30.6%
  • At week 2 and 8, the mean percent changes in VAS score were similar for patients regardless of age (70 y and below vs. above 70 y): week 2: 28.6%versus 23.6%; week 8: 29.3% versus 32.4% 

 

​Fig.1. Percentage of patients with a ≥ 30%, 50%, or 20 mm reductions in the VAS from baseline to week 8

  • Total 45.8% of all patients had a ≥ 30% reduction in VAS score from baseline to week 2, and 53.2% had ≥ 30% reduction in VAS score at week 8
  • The proportion of patients who had a ≥ 50% reduction in VAS score from baseline was 33.2% at week 2 and 40.5% at week 8, and 37.4% of patients had a reduction in VAS score from baseline of ≥ 20mm at week 2, which increased to 51.1% by week 8      
  • Secondary outcomes:           
  • This included BPI, which measured changes in worst pain, least pain and average pain and degree to which pain interferes with their life and activities      
  • On the PGIC instrument, more patients aged 70 years and below reported feeling “much” or “very much” improved from baseline (59.0% vs. 40.3%) ; CGIC: 61.9% versus 41.6%

 

Fig.2. Responders according to PGIC and CGIC

  • The most common G-GR-related AEs (70 y and below/above 70 y) were dizziness (11.7%/16.3%) and somnolence (3.6%/8.1%)     
Conclusion: 

Result shows that G-GR reduced pain intensity, improved patients’ quality of life, improved sleep and was well tolerated. Nearly half of the patients (42.6%) was taking a concomitant pain medication at baseline, with opioids (28.9%) and anticonvulsants (13.2%) used most frequently.

However, as measured by the VAS, (BPI), CGIC, and PGIC instruments reductions in pain or the effect of pain on quality of life were similar regardless of whether patients used any concomitant medication, suggesting that G-GR alone provided sufficient pain relief.

Clin J Pain. 2015 Jan; 31(1):58-65
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