A Phase 2a Study to Assess Safety & Pharmacokinetics of Sustained Release Sodium Nitrite in Patients With Diabetic Pain

The primary objective of this clinical study is to evaluate the safety and tolerability of multiple doses of twice daily 40mg and 80mg sustained release sodium nitrite compared with placebo over a 12 week treatment period. The following safety parameters will also be assessed: concomitant medication usage, physical examination, vital signs, Comprehensive Metabolic Panel, and complete blood count. Assessment of acute adverse events (i.e., drop in blood pressure, dizziness) after administration of each dose level. Counts are number of subjects reporting at least 1 Adverse Event. The total Adverse Events recorded in each cohort is also reported.

Blood levels of nitrite will be assessed for 6 hours post-administration on the initial dosing visit.

Daily patient reported use of analgesic or medications for neuropathic pain. The use of medications were recorded at the baseline visit and during both the intermediate and final visit for each subject. All subjects used at least one prescription pain medication, other than one subject in the 80-mg dose cohort who used only ibuprofen to control pain. Most subjects used more than one prescription pain medication. There was no change in use of pain medications during the trial period.

Subjects completed the Brief pain inventory (BPI), RAND 36 questionnaire, neuropathic pain symptom inventory (NPSI) and Short Form McGill Pain Questionnaire at each visit for these self-reported questionnaires. The BPI is a questionnaire that measures the patient's subjective perception of pain, its exacerbating and alleviating factors, and perceived effect on functional status; the NPSI is a questionnaire that measures the symptoms associated with neuropathic pain; the Short Form McGill Questionnaire subjectively assesses the patients perception of pain described by commonly used adjectives associated with pain. NPSI is average of 12 questions, range from 0 (no pain) to 120 (maximal pain); For BPI severity and interference, questions are scored from 0-10, then there average score for each subsection is calculated (the higher the score, the worse the response); Scores on McGill range from 0-10, lower associated for less pain, then averaged for each sub score and total score.

Quantitative sensory testing (QST) was conducted at each visit to determine patients sensitivity to pain. QST was assessed using a quantitative nerve conductance machine where nerves in the distal extremity are subjected to electrical stimulation to determine the sensory threshold of the skin. Nerve conductance measures how fast an electrical impulse moves through the nerve, and nerve velocity measures the speed at which an electrical impulse moves down a neuronal pathway.

HbA1C levels will be monitored at each visit to determine whether treatment reduces circulating glucose levels.

Pulse oximetry will be used at each visit to determine whether treatment improves oxygen levels in the blood.