On 2015 Jan 21, David Keller commented:

Vitamin C was administered orally in this study

When vitamin C is ingested orally, the serum concentration is regulated to a maximum of about 300 microM/L. Intravenous administration of vitamin C bypasses enteric control mechanisms, allowing plasma concentrations of up to 20,000 microM/L to be achieved. Alternative practitioners claim special benefits at the supra-physiologic concentrations which can only be achieved with IV administration. This comment is not meant to support or dispute their claims, it is placed here for the reference of researchers who do not have access to the NEJM archives, since the route of administration is not mentioned in the PubMed abstract.

On 2015 Jan 21, David Keller commented:

Vitamin C was administered orally in this study

When vitamin C is ingested orally, the serum concentration is regulated to a maximum of about 300 microM/L. Intravenous administration of vitamin C bypasses enteric control mechanisms, allowing plasma concentrations of up to 20,000 microM/L to be achieved. Alternative practitioners claim special benefits at the supra-physiologic concentrations which can only be achieved with IV administration. This comment is not meant to support or dispute their claims, it is placed here for the reference of researchers who do not have access to the NEJM archives, since the route of administration is not mentioned in the PubMed abstract.