The efficacy and safety of the low concentration [0.65% (50 µg/cm2) and 1.25% (100 µg/cm2)] capsaicin patches and compared them to conventional 0.075% capsaicin cream and placebo patch in patients suffering from peripheral neuropathy

Inclusion Criteria:

• patients who are 18 years of age or older aged having chronic peripheral neuropathy related with a diagnosis of either PHN or DPN
• patients with chronic peripheral neuropathic pain for more than 3 months with an 11-pointed Numeric Rating Scale (NRS) pain score ≥ 4
• patients with a diagnosis of PHN were eligible if at least 3 months had elapsed since shingles vesicle crusting
• patients with DPN and well controlled diabetes were asked to maintain a stable dose of oral hypoglycemic or insulin during the study period
• patients taking concomitant pain medications such as anticonvulsants, antidepressants, anxiolytics, and opioids including tramadol were required to maintain a stable dose for at least 4 weeks before the study enrollment
• any conservative therapies such as TENS, physical therapy, chiropractic, massage, biofeedback, or yoga were stopped at least 5 weeks before the enrollment
• women of childbearing age were required to have a negative pregnancy test and were to be willing to use an effective method of contraception for at least 28 days after the last exposure to study medication

Exclusion Criteria:

• diffusely distributed neuropathic pain resulting from spinal stenosis, postoperative origin, complex regional pain syndrome, or genetic neurological disease, or significant pain outside the target area
• significant pain of an etiology other than PHN or DNP
• other severe acute or chronic medical or psychiatric condition, or laboratory abnormality that may increase the risk associated with study participation or with investigational product administration or may interfere with compliance or the interpretation of study results andin the judgment of the investigator would make the subject inappropriate to participate in the study
• painful PHN areas located on the face or above the scalp hairline
• an implanted medical device for the treatment of neuropathic pain
• use of topically applied agents including capsaicin-containing products, a 5% lidocaine patch or similar products, local anesthetics, or steroids within the past 21 days
• hypersensitivity known to capsaicin; current use of any class 1 anti-arrhythmic drug; and uncontrolled diabetes mellitus or uncontrolled hypertension
• If patients have taken oral NSAID or COX2 Inhibitor, it should be stopped at least2 weeks before randomization; however acetaminophen for pain control was allowed up to 4g per day