What medications can interact with chamomile, especially in patients with a history of bleeding disorders, liver or kidney disease, or those taking multiple medications?

Chamomile Drug Interactions

Chamomile can potentiate warfarin and other anticoagulants, increasing bleeding risk, and should be avoided or used with extreme caution in patients taking these medications. 1, 2

High-Risk Interactions: Anticoagulants and Antiplatelet Agents

Warfarin (Highest Risk)

• Chamomile contains coumarin constituents that theoretically potentiate warfarin's anticoagulant effects 1, 3
• A documented case report describes a 70-year-old woman on warfarin who developed multiple internal hemorrhages after using chamomile tea and body lotion for upper respiratory symptoms 2
• The FDA warfarin label specifically lists chamomile among botanicals that may increase anticoagulant effects 1
• Monitor INR closely if chamomile cannot be discontinued; ideally, avoid concurrent use entirely 1, 4

Other Anticoagulants and Antiplatelet Drugs

• Chamomile's antiplatelet and anticoagulant properties create additive bleeding risk when combined with aspirin, clopidogrel, prasugrel, ticagrelor, or other antiplatelet agents 3, 5
• The same bleeding risk applies to direct oral anticoagulants (DOACs: apixaban, rivaroxaban, dabigatran, edoxaban), though less well-documented than with warfarin 6, 3
• NSAIDs combined with chamomile and any anticoagulant create particularly high bleeding risk through multiple mechanisms 6

Moderate-Risk Interactions

Sedative Medications

• Chamomile has mild sedative properties that may potentiate CNS depressants including benzodiazepines, barbiturates, opioids, and sleep medications 3
• Advise patients to avoid driving or operating machinery if combining chamomile with sedatives 3

Cytochrome P450 Substrates

• Chamomile may theoretically affect CYP450 enzyme activity, though clinical significance remains poorly documented 3, 7
• Exercise caution with narrow therapeutic index drugs metabolized by CYP450 enzymes (e.g., phenytoin, carbamazepine, certain statins) 7, 4

Special Population Considerations

Patients with Bleeding Disorders

• Absolute avoidance of chamomile is recommended in patients with hemophilia, thrombocytopenia, or other bleeding diatheses 2, 5
• The antiplatelet effects of chamomile alone may precipitate bleeding even without concurrent anticoagulant therapy 3, 5

Hepatic or Renal Impairment

• Patients with liver disease have impaired coagulation factor synthesis, making them more susceptible to chamomile's anticoagulant effects 6, 1
• Renal impairment increases bleeding risk with anticoagulants; chamomile adds further risk if these drugs are co-administered 6

Polypharmacy Patients

• Systematically review all medications, including over-the-counter products and supplements, before allowing chamomile use 6
• The cumulative effect of multiple interacting substances is unpredictable and potentially dangerous 1, 4

Clinical Management Algorithm

Before Initiating Chamomile

1. Screen for all anticoagulant/antiplatelet medications (prescription and OTC aspirin) 1, 4
2. Assess bleeding history and current bleeding risk factors 2, 5
3. If patient is on warfarin or other anticoagulants, strongly discourage chamomile use 1, 2

If Patient Insists on Using Chamomile with Anticoagulants

1. For warfarin: Check baseline INR, then recheck within 3-7 days of starting chamomile 1, 4
2. Continue weekly INR monitoring for at least one month 1, 4
3. Educate patient to report any unusual bleeding, bruising, dark stools, or blood in urine immediately 1, 2
4. Document the interaction risk and patient's decision in medical record 2, 4

If Bleeding Occurs

1. Discontinue chamomile immediately 2
2. Check INR/PT if on warfarin; assess platelet function if on antiplatelet agents 1, 2
3. Manage bleeding per standard protocols; consider vitamin K for warfarin-related bleeding 1

Critical Pitfalls to Avoid

• Never assume topical chamomile products (lotions, creams) are safe—systemic absorption can occur 2
• Do not rely on "modest consumption" being safe; the documented case involved routine chamomile tea use 2
• Avoid dismissing chamomile as "just an herb"—it contains pharmacologically active coumarins 1, 3
• Remember that chamomile products lack standardization; potency varies widely between preparations 1, 3

Evidence Quality Note

Most chamomile interaction data derives from case reports, in vitro studies, and theoretical mechanisms rather than controlled trials 3, 4. However, the documented case of severe bleeding with warfarin, combined with FDA recognition of the interaction and chamomile's known coumarin content, justifies treating this as a clinically significant interaction 1, 2. The consistency of reports across multiple anticoagulant botanicals supports a cautious approach 4.