USE OF INTRATHECAL SNX-111, A NOVEL, N-TYPE, VOLTAGE-SENSITIVE, CALCIUM-CHANNEL BLOCKER, IN THE MANAGEMENT OF INTRACTABLE BRACHIAL-PLEXUS AVULSION PAIN

Objective: The objective was to assess the analgesic, antihyperesthesi c, and antiallodynic properties of SNX-111 in neuropathic pain. Design : We describe a patient with refractory, severe deafferentation pain s uccessfully treated with SNX-111 in an open-label, baseline-controlled Phase I/II trial. Setting: The patient was hospitalized for treatment and observation. Patient: The patient was a 43-year-old man with intr actable deafferentation pain of 23 years' duration secondary to brachi al plexus avulsion. Intervention: SNX-111, the first neuron-specific, N-type, voltage-sensitive calcium channel blocker developed for clinic al use, was administered by continuous, constant-rate, intrathecal inf usion via an indwelling cervical catheter. Outcome Measures: The prima ry outcome measures were the Visual Analog Scales of Pain Intensity (V ASPI) and Pain Relief (VASPR). Results: The patient experienced comple te pain relief (VASPI = 0.0 cm and VASPR = 10.0 cm) with elimination o f hyperesthesia and allodynia. Conclusions: SNX-111, administered intr athecally by continuous, constant-rate infusion, produced dose-depende nt pain relief in a 43-year-old male patient with a 23-year history of intractable deafferentation and phantom limb pain secondary to brachi al plexus avulsion and subsequent amputation. Dizziness, blurred visio n, and lateral-gaze nystagmus were dose-dependent side effects that re solved with decreasing dose levels. Complete pain relief was achieved in this patient without side effects after dose adjustment. We conclud e that SNX-111 is a potent analgesic, antihyperesthesic, and antiallod ynic agent. Controlled studies of SNX-111 in patients with malignant a nd nonmalignant pain syndromes are warranted and are under way.