Relief of Acute Herpetic Pain by Intravenous Vitamin C: The Dosage May Make a Difference.

Dear Editor:

Intravenous high-dose vitamin C is a promising method for mitigating acute herpetic pain (AHP) and postherpetic neuralgia (PHN)123. We are interested in the research by Kim et al.4 on the efficacy of intravenous vitamin C (5 g every second day for 3 times) on relieving AHP and decreasing the incidence of PHN. Although the incidence of PHN in the vitamin C group was significantly lower compared to that in the control group, no significant differences were noted in the intensity of AHP between the two groups. Therefore, Kim et al.4 concluded that intravenous vitamin C was ineffective in relieving AHP.

In describing the rationale for choosing the dosage of intravenous vitamin C, Kim et al.4 cited 3 references in which “effect of vitamin C has been reported at a dose of 2.5 g in PHN and at a dose of 7.5 g, 15 g in acute phase.” Of these references regarding AHP, 1) Schencking et al.2 reported total remission of the cutaneous lesions and AHP in 2 patients with shingles after intravenous vitamin C 15 g every second day for total doses of 60 and 90 g, respectively; 2) a prospective cohort study3, in which shingles patients received intravenous infusions of vitamin C (7.5 g for 2 to 4 times per week, for approximately 2 weeks) in addition to standard treatment, concluded that vitamin C at an average total dose of 60 g effectively reduced AHP. In the research by Kim et al.4, however, intravenous vitamin C in a total dose of 15 g was surprisingly low in view of the above-mentioned references. More importantly, there was no data on the efficacy of vitamin C greater than 15 g on AHP in that study. Kim et al.4 concluded that intravenous vitamin C was ineffective in relieving AHP; however, effects of vitamin C have been demonstrated to be dose-dependent5.

Recently, we had successful experience of relieving AHP by intravenous high-dose vitamin C (5 g/d) in one female. On the third day of intravenous vitamin C therapy (for a cumulative dose of 15 g), AHP was not relieved at all. This finding was compatible with that of Kim et al.4 Further treatment with intravenous vitamin C, however, brought about obvious reduction of pain intensity, frequency and duration of each pain episode in one week. The patient received a total of 35 g of intravenous vitamin C. In conclusion, while the efficacy of high-dose vitamin C on AHP is not yet conclusive, the conclusion by Kim et al.4 that intravenous ascorbic acid did not relieve AHP effectively was unjustified. Our case supported the valuable finding by Kim et al.4 that intravenous vitamin C in a total dose of 15 g was not enough for relieving AHP. Nonetheless, a more proper conclusion is that a total dose 15 g of intravenous ascorbic acid did not effectively relieve AHP.