Theophylline (drug interactions)

DEFINITION: Once among the most common treatments for asthma, theophylline is no longer widely used, having been replaced by drugs that cause fewer side effects.

• INTERACTIONS: Various prescription medications, cayenne, ipriflavone, St. John’s wort, ephedra, guarana, tannin-containing herbs, vitamin B₆
• TRADE NAMES: Theo-24, Elixophyllin
• DRUGS IN THIS FAMILY: Aminophylline (generic), choline theophyllinate (Not available in the US)

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 theophylline's many side effects 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 the Action of the 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, leading 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.

Other interactions

By the twenty-first century, researchers had discovered hundreds of drugs that interact with theophylline, with interactions ranging from major to minor. Many of these medications treat conditions for which theophylline is not advised, including gastroesophageal reflux disease (GERD), renal dysfunction, seizure disorders, and tachyarrhythmias. Patients should not consume excessive caffeine while taking theophylline, and they should avoid guarana. Other herbs and supplements that interact with theophylline include ephedra, which may stimulate the central nervous system and cause rapid heartbeat. Tannins, like those found in tea, can decrease the absorption of theophylline, as can charbroiled meat and cruciferous vegetables. Patients taking certain antibiotics, seizure medications, and heartburn medications should consult their doctor before adding theophylline.

Bibliography

Bartel, P. R., et al. "Vitamin B6 Supplementation and Theophylline-Related Effects in Humans." American Journal of Clinical Nutrition, vol. 60, 1994, pp. 93-99.

Czigle, Szilvia, et al. "Pharmacokinetic and Pharmacodynamic Herb-Drug Interactions—Part I. Herbal Medicines of the Central Nervous System." PeerJ, vol. 11, 2023, doi.org/10.7717/peerj.16149. Accessed 15 Dec. 2025.

Jobst, K. A., et al. "Safety of St. John’s Wort (Hypericum perforatum)." The Lancet, vol. 355, 2000, pp. 575.

Kahn, Sonia, et al. "Theophylline Interactions." The Pharmaceutical Journal, 10 July 2014, pharmaceutical-journal.com/article/ld/theophylline-interactions. Accessed 15 Dec. 2025.

McIntyre, Chelsey. “Theophylline (Theo-Dur, Theo-24, and Others) - Uses, Side Effects, and More.” WebMD, 31 Oct. 2024, www.webmd.com/drugs/2/drug-3591-3076/theophylline-oral/theophylline-sustained-release-oral/details. Accessed 15 Dec. 2025.

Nebel, A., R. K. Baker, and D. J. Kroll. "Potential Metabolic Interaction Between Theophylline and St. John’s Wort." Annals of Pharmacotherapy, vol. 33, no. 4, 1999, p. 502.

Shimizu, T., et al. "Theophylline Attenuates Circulating Vitamin B6 Levels in Children with Asthma." Pharmacology, vol. 49, 1994, pp. 392-397.

"Theophylline." MedlinePlus, 15 Nov. 2019, medlineplus.gov/druginfo/meds/a681006.html. Accessed 15 Dec. 2025.

"Theophylline (Oral Route)." Mayo Clinic, 1 Oct. 2025, www.mayoclinic.org/drugs-supplements/theophylline-oral-route/description/drg-20073599. Accessed 15 Dec. 2025.