What is theophylline? How does it interact with other drugs?

Vitamin B6

Effect: Supplementation Possibly Helpful

Theophylline appears to impair the normal conversion of vitamin B6
into the more active substance pyridoxal 5’-phosphate (PLP). These findings have led some researchers to suspect that some of the many side effects of theophylline could be caused, in part, by interference with B6 activity. Indeed, one study found that B6 supplements might help reduce theophylline-induced tremors.

St. John’s Wort

Effect: Possible Interference with Action of Drug

Evidence suggests that the herb St. John’s wort can lower blood levels of theophylline, making it less effective.

Cayenne

Effect: Possible Increased Risk of Toxicity

Oral cayenne might increase the absorption of theophylline, which could lead to an increased risk of theophylline toxicity.

Ipriflavone

Effect: Possible Increased Risk of Toxicity

Like cayenne, the supplement ipriflavone may increase levels of theophylline in the body, possibly increasing the risk of toxicity.

Bibliography

Bartel, P. R., et al. “Vitamin B6 Supplementation and Theophylline-Related Effects in Humans.” American Journal of Clinical Nutrition 60 (1994): 93-99.

Jobst, K. A., et al. “Safety of St. John’s Wort (Hypericum perforatum).” The Lancet 355 (2000): 575.

Nebel, A., R. K. Baker, and D. J. Kroll. “Potential Metabolic Interaction Between Theophylline and St. John’s Wort.” Annals of Pharmacotherapy 33, no. 4 (1999): 502.

Shimizu, T., et al. “Theophylline Attenuates Circulating Vitamin B6 Levels in Children with Asthma.” Pharmacology 49 (1994): 392-397.