Once among the most common treatments for asthma, theophylline is no longer widely used, having been replaced by drugs that cause fewer side effects.
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
activity. Indeed, one study found that B
6 supplements might help reduce theophylline-induced tremors.5
Evidence suggests the herb St. John's wort can lower blood levels of theophylline, making it less effective.6,7
Oral cayenne might increase the absorption of theophylline,8
which could lead to an increased risk of theophylline toxicity.
Like cayenne, the supplement ipriflavone may increase levels of theophylline in the body, possibly increasing the risk of toxicity.9
Shimizu T, Maeda S, Mochizuki H, et al. Theophylline attenuates circulating vitamin B
levels in children with asthma.
49: 392–397, 1994.
Martinez de Haas MG, Poels PJ, de Weert CJ, et al. Subnormal vitamin B
levels in theophylline users.
Ned Tijdschr Geneeskd
141: 2176–2179, 1997.
Ubbink JB, Delport R, Bissbort S, et al. Relationship between vitamin B
status and elevated pyridoxal kinase levels induced by theophylline therapy in humans.
120: 1352–1359, 1990.
Delport R, Ubbink JB, Vermaak WJ, and Becker PJ. Theophylline increases pyridoxal kinase activity independently from vitamin B
Res CommunChem Pathol Pharmacol
79: 325–333, 1993.
Bartel PR, Ubbink JB, Delport R, et al. Vitamin B
supplementation and theophylline-related effects in humans.
Am J Clin Nutr
60: 93–99, 1994.
Nebel A, Baker RK, and Kroll DJ. Potential metabolic interaction between theophylline and St. John's wort.
33(4): 502, 1999.
Jobst KA, McIntyre M, St. George D, et al. Safety of St. John's wort
355(9203): 575, 2000.
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.
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.
Last reviewed December 2015 by EBSCO CAM Review Board
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