Nutrient deficiencies as a risk factor in Taiwanese patients with postherpetic neuralgia.

Postherpetic neuralgia (PHN) is the most common complication of herpes zoster (HZ). The aim of the present study was to compare the nutritional status of PHN patients with that of healthy controls, and then to identify risk factors for PHN using multivariate multiple logistic regressions. In the present cross-sectional study, we prospectively enrolled fifty PHN patients for at least 3 months and fifty healthy controls. We selected nine circulating nutrients including ionised Ca, Zn, retinol, folic acid, vitamin B12, vitamin C, α-tocopherol, γ-tocopherol and lycopene associated with both immunity and the modulation of neuropathic pain, and measured their concentrations in plasma/serum. Concentrations of ionised Ca, Zn, vitamin C and vitamin B12 were significantly lower in PHN patients than in controls after excluding those patients receiving supplements since the outbreak of HZ. The prevalence of either mild/marginal or severe deficiencies for any of the nine selected circulating nutrients in PHN patients (92 %) was much higher than that in controls (46 %) (P < 0·001). Lower concentrations of vitamin C ( ≤ 45·0 µmol/l), ionised Ca ( ≤ 1·05 mmol/l) and Zn ( ≤ 0·91 g/l) were found to increase independently the risk of PHN using binary variable (dichotomy) analyses with both PHN patients and controls in a multivariate logistic regression analysis. No significant correlations existed between the risks of PHN and the concentrations of retinol, folic acid, vitamin B12, lycopene or α:γ-tocopherol ratios. Thus, lower concentrations of circulating nutrients, namely vitamin C, ionised Ca or Zn, are probably a risk factor in Taiwanese patients with PHN.

Plasma vitamin C is lower in postherpetic neuralgia patients and administration of vitamin C reduces spontaneous pain but not brush-evoked pain.

OBJECTIVES: Plasma vitamin C concentrations have been suggested to be related to pain modulation in postherpetic neuralgia (PHN), an intractable neuropathic pain syndrome. In this study, we first compared plasma concentrations of vitamin C between healthy volunteers and PHN patients and then designed a symptom-based and mechanism-based approach to assess the analgesic effect of intravenous vitamin C on spontaneous and brush-evoked pain. METHODS: Study 1 was cross-sectional that enrolled 39 healthy volunteers and 38 PHN patients. Study 2 was a double-blinded, placebo-controlled intervention study, which comprised 41 patients randomly allocated into the ascorbate group and placebo. Each patient received normal saline infusion with or without ascorbate on days 1, 3, and 5 and answered questionnaires that included side effects; numeric rating pain scale (NRS) on spontaneous and brush-evoked pain on days 1, 3, 5, and 7; and patient global impression of change on spontaneous and brush-evoked pain on day 7. RESULTS: Study 1 revealed that plasma concentrations of vitamin C were significantly lower in patients with PHN than in healthy volunteers (P<0.001). Study 2 showed that ascorbate treatment effectively restored plasma vitamin C concentrations in the patients and decreased spontaneous pain by 3.1 in NRS from baseline to day 7, as compared with a decrease of 0.85 in NRS by placebo treatment (P<0.001). Conversely, ascorbate treatment did not significantly affect brush-evoked pain. Ascorbate treatment also resulted in a better efficacy than placebo in patient global impression of change on spontaneous pain (P<0.001) on day 7 and did not affect brush-evoked pain. No side effects were observed. CONCLUSIONS: Plasma vitamin C status plays a role in PHN, and intravenous ascorbate helps relieve spontaneous pain in PHN.