A 78-yr-old male suffered from intractable T3-6 postherpetic neuralgia. He reported 8 mo of constant, aching pain and intermittent, spontaneous, shooting pain over his right anterior chest and upper back. His pain did not respond to multiple trials of antidepressants and anticonvulsants. Pain intensity ranged from 4 to 8 on an 11-point numerical pain rating scale. The pain he rated 8 occurred in 5-min episodes for about 8–10 times per day. His appetite was poor, he bruised easily, and his gums were swollen. Laboratory data were normal except for a low concentration of plasma vitamin C (4.9 mg/L), consistent with poor nutrition.
We treated this patient with IV 2.5 g ascorbate daily on days 1, 3, and 5. His intermittent, spontaneous, shooting pain completely resolved within 1 wk, and his baseline pain decreased to a level of 3 (his plasma vitamin C level reached 14.9 mg/L). We advised him to increase his intake of fruits and vegetables. On follow-up examination 3 mo later he has had no recurrence of the extreme intermittent pain, and his plasma vitamin C level was 11.6 mg/L.
Hanck and Weiser reported a dose-dependent pain reduction by oral vitamin C in rats. Ascorbate is an antioxidant that scavenges reactive oxygen species (ROS). ROS play a crucial role in neuropathic pain. By enhancing adenylyl cyclase-cAMP, ascorbic acid can also augment the production and the release of ß-endorphin from rat hypothalamic neurons. ß-Endorphin appears to be effective in alleviating neuropathic pain.
Formal studies are required to determine whether treatment with vitamin C may prove useful in patients with low plasma vitamin C and neuropathic pain.