Liquid Capsaicin (NGX-1998) Provides PHN Relief After Five Minutes

HONOLULU, HI —At the American Pain Society's 31st Annual Scientific Meeting, investigators reported that a 5-minute application of NGX-1998, a novel liquid formulation of high concentration capsaicin (10% and 20% w/w) provided effective pain relief for up to 12 weeks for the management of peripheral neuropathic pain associated with postherpetic neuralgia (PHN).  

Capsaicin 8% (Qutenza) is available in a patch formulation that provides 12 weeks of PHN pain relief following a single 60-minute application. NGX-1998 was studied in a 12-week, multicenter, placebo-controlled, double-blind trial in PHN patients to determine if it could deliver similar or better efficacy, safety, and tolerability following a 5-minute application. Using a 2:2:1 (10%: 20%: placebo) randomization, 164 patients received a 5-minute topical application of NGX-1998 or placebo to their area of pain. The primary endpoint was mean percent change from baseline in average pain for the past 24 hours during Weeks 2–8; secondary endpoint was the mean percent change during Weeks 2–12.

Using the Numeric Pain Rating Scale (NPRS), patients recorded their scores daily during Weeks 2–12.   A clear dose-response was observed in the mean percent change in average pain from baseline at Week 8: -25.1%, -22.3%, and -16.7% for the NGX-1998 20%, 10%, and placebo groups, respectively. At week 12, mean percent change in average pain was -26.0%, -22.2%, and -16.6% for the 20%, 10%, and placebo groups, respectively. The study was not powered to determine a statistically significant difference between the 20% and 10% formulations.

The patients' dermal assessment scores ranged from 0–2 (0=no irritation, 1=mild erythema, 2= definite erythema, minimal papules/edema). The most common adverse effects were localized dermal reactions (eg, pain and erythema). Severe and serious adverse effects were more prevalent in the placebo group. NGX-1998 was well-tolerated at both doses and resulted in improved outcomes on validated measures of neuropathic pain.

Lynn Webster, MD, from Lifetree Clinical Research, Salt Lake City, UT, and colleagues, concluded that a 5-minute application of NGX-1998 may provide a convenient option to patients with PHN that could reduce healthcare provider time.