What happens when you take digoxin with hawthorn?
Digoxin is a narrow-therapeutic-index cardiac glycoside derived historically from the foxglove plant. It is used to slow the ventricular rate in atrial fibrillation and to provide modest inotropic support in heart failure. Even small swings in digoxin level can move a patient from sub-therapeutic to toxic, so anything that interferes with its absorption, distribution, or measurement deserves attention.
Hawthorn (Crataegus oxyacantha or Crataegus monogyna) is a herbal traditionally used for cardiac symptoms, mild heart failure, and palpitations. Like digoxin, hawthorn extracts have mild positive inotropic and vasodilatory effects, although via different molecular targets including potassium channel and phosphodiesterase modulation. Hawthorn constituents may also influence the P-glycoprotein efflux pump that handles digoxin transport, although the clinical magnitude is uncertain.
A 2003 crossover study (Tankanow et al.) co-administered hawthorn extract WS 1442 at 900 mg/day with digoxin for three weeks and found no statistically significant change in digoxin pharmacokinetics. That suggests the pharmacokinetic risk is small at typical hawthorn doses. The remaining concerns are pharmacodynamic (additive cardiac effects) and analytical (interference with digoxin immunoassays).
Why is this important?
Because hawthorn has cardiac-active compounds with structural similarities to digoxin glycosides, it can artifactually inflate the digoxin level reported by certain immunoassays. A patient who appears to have a digoxin level of 1.4 ng/mL when actually it is 0.9 ng/mL may have their dose mistakenly reduced, leading to under-treatment of their atrial fibrillation or heart failure. The reverse — falsely low readings — is also possible depending on the assay format. Modern liquid chromatography mass spectrometry assays can resolve this, but most hospital labs use immunoassays.
Pharmacodynamically, both substances slow conduction and provide inotropic support. In a patient with reduced ejection fraction, additive effects from hawthorn could in principle precipitate bradycardia or arrhythmia, but the magnitude is small and has not been characterized in clinical trials. The Memorial Sloan Kettering About Herbs page summarizes this nicely: laboratory data suggest theoretical interaction, but a small clinical trial found safe coadministration; clinical relevance remains undetermined and use should be under physician guidance.
What should you do?
Do not start hawthorn while taking digoxin without your cardiologist's explicit approval. If you are already taking both, do not stop digoxin or hawthorn abruptly without a plan. Tell your prescriber what hawthorn product, dose, and duration you have been using so they can interpret digoxin levels in context and consider ordering a more specific assay if a level is in the borderline-high range.
If your indication for digoxin is rate control in atrial fibrillation or heart failure with reduced ejection fraction, a serious conversation about replacing hawthorn is warranted — there is no high-quality evidence that hawthorn adds benefit on top of evidence-based heart failure therapy, and the modest risks of confounded digoxin monitoring are not worth the unproven upside.
Which specific products are affected?
Hawthorn is sold as leaf and flower extract, berry extract, and combination products. Common standardized extracts include WS 1442 (used in many European studies) and HeartCare. Products vary widely in dose and standardization (oligomeric procyanidins or vitexin content), so two different bottles labeled hawthorn are not equivalent. The studied dose in the Tankanow pharmacokinetic study was 900 mg/day of WS 1442.
Digoxin is sold under the brand names Lanoxin and Digox and as generic digoxin in tablet and oral solution forms. The considerations apply equally to all forms because the interaction is pharmacodynamic and analytical, not formulation-specific.
The bottom line
Digoxin and hawthorn is a moderate interaction. Formal pharmacokinetic studies show little change in digoxin AUC, but hawthorn has additive cardiac effects and interferes with common digoxin immunoassays, which can lead to dosing errors. The safest practice is to avoid hawthorn while on digoxin unless your cardiologist approves, and to always disclose hawthorn use to any lab or clinician interpreting your digoxin level.