Efficacy and Safety of Pregabalin in Treatment of Neuropathic Pain in Patients With Idiopathic Small Fiber Neuropathy

Efficacy and Safety of Pregabalin in Treatment of Neuropathic Pain in Patients With Idiopathic Small Fiber Neuropathy

The purpose of this study is to assess safety and efficacy of treatment with pregabalin in patients with idiopathic small fiber neuropathy proven by skin biopsy.This is an enriched enrollment randomized withdrawal study that comprises 4 phases: a screening and selection phase, a washout period from previous pain medication for enriched enrollment, an 8 week single blind pregabalin treatment phase; and a 4 week randomized withdrawal phase.

Patients who show any increase in their pain intensity score during the washout phase will be eligible for the single blind pregabalin treatment phase. Patients who respond to pregabalin, with at least 1 point improvement in neuropathic pain from baseline at the end of the single blind pregabalin treatment phase and meeting all other study requirements are considered eligible for participation in the withdrawal phase. These eligible patients are randomly assigned (1:1) to continue pregabalin or to be switched to placebo for a comparison of pregabalin efficacy and safety. Patients who have a worsening of average pain relative to the last week of the single blind pregabalin treatment period by more than one point and average pain level > =4 will be considered to have a loss of therapeutic response (LTR).

Inclusion Criteria:

• Subjects with idiopathic predominate-small fiber neuropathy
• Subject must have chronic peripheral neuropathic pain for more than 3 months
• A score >3 and <8 on Pain intensity scale for pain in prior week at first visit;
• Show increase in pain intensity scores during the wash off period;
• Age older than 18 years;

Exclusion Criteria:

• Subjects with large-fiber predominant neuropathy
• Subjects with HIV infection, trigeminal neuralgia (TGN), toxic neuropathy (e.g. chemotherapy exposure), paraneoplastic neuropathy, mono-gammopathy, inflammatory neuropathy, celiac disease, systemic lupus, peripheral vascular disease, connective tissue disorders, hepatitis C, Fabry disease, and diabetes;
• Subjects with uncontrolled thyroid or B12 disorders
• Subjects with Complex Regional Pain Syndrome
• Allergy to Pregabalin
• Subjects at risk of suicide or self harm
• Subjects with any clinically unstable cardiovascular, hematological, autoimmune, endocrine, renal, hepatic, renal, respiratory, or gastrointestinal disease; epilepsy, symptomatic peripheral vascular disease including intermittent claudication, pernicious anemia, untreated hypothyroidism, venous insufficiency, or spinal stenosis.
• History of known analgesic, alcohol or illicit drug abuse within 12 months of first visit;
• Pregnant females; breastfeeding females.