Clinical evidence,mechanism, importance and management
A man with a history of manic behaviour,taking fluphenazine 15mg daily, had a 25 % reduction in his plasma fluphenazine levels, from 0.93 to
nanograms/mL,over a 13-day period while taking ascorbic acid 500mg twice daily. This was accompanied by a deterioration in his behaviour (See reference number 1). The reason for this effect is not understood. There seem to be no other reports of this interaction with fluphenazine or any other phenothiazine so that this interaction would not appear to be of general importance.
Dysken MW,Cumming RJ, Channon RA, Davis JM. Drug interaction between ascorbic acidand fluphenazine. JAMA (1979) 241, 2008.