Theophylline appears to impair the normal conversion of vitamin B
6
into the more active substance pyridoxal 5'-phosphate (PLP).
1–4
These findings have led some researchers to suspect that some of the many side effects of theophylline could be caused, at least in part, by interference with B
6
activity. Indeed, one study found that B
6
supplements might help reduce theophylline-induced tremors.
5
Shimizu T, Maeda S, Mochizuki H, et al. Theophylline attenuates circulating vitamin B
6
levels in children with asthma.
Pharmacology
49: 392–397, 1994.
2
Martinez de Haas MG, Poels PJ, de Weert CJ, et al. Subnormal vitamin B
6
levels in theophylline users.
Ned Tijdschr Geneeskd
141: 2176–2179, 1997.
3
Ubbink JB, Delport R, Bissbort S, et al. Relationship between vitamin B
6
status and elevated pyridoxal kinase levels induced by theophylline therapy in humans.
J Nutr
120: 1352–1359, 1990.
4
Delport R, Ubbink JB, Vermaak WJ, and Becker PJ. Theophylline increases pyridoxal kinase activity independently from vitamin B
6
nutritional status.
Res CommunChem Pathol Pharmacol
79: 325–333, 1993.
5
Bartel PR, Ubbink JB, Delport R, et al. Vitamin B
6
supplementation and theophylline-related effects in humans.
Am J Clin Nutr
60: 93–99, 1994.
6
Nebel A, Baker RK, and Kroll DJ. Potential metabolic interaction between theophylline and St. John's wort.
Ann Pharmacother
33(4): 502, 1999.
7
Jobst KA, McIntyre M, St. George D, et al. Safety of St. John's wort
(Hypericum perforatum).Lancet
355(9203): 575, 2000.
8
Bouraoui A, Toumi A, Mustapha HB, et al. Effects of capsicum fruit on theophylline absorption and bioavailability in rabbits.
Drug Nutr Interact
5: 345–350, 1998.
9
Monostory K and Vereczkey L. The effect of ipriflavone and its main metabolites on theophylline biotransformation.
Eur J Drug Metab Pharmacokinet
21(1): 61–66, 1996.
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