Chamomile

Chamomile aqueous extracts have demonstrated hypoglycemic activity in animal models and human pilot studies, attributed to the flavonoid apigenin which inhibits aldose reductase and modulates insulin secretion. Co-administration with antidiabetic medications may produce additive blood glucose lowering.

Monitor blood glucose in diabetic patients using chamomile supplements. The interaction is low risk at typical chamomile tea consumption levels but warrants monitoring with concentrated extracts.

Chamomile contains coumarin-type constituents (herniarin, umbelliferone) with intrinsic anticoagulant activity that synergize with warfarin. Additionally, chamomile essential oil inhibits CYP2C9 in vitro, reducing S-warfarin metabolism and elevating plasma warfarin levels. A published case report documented multiple internal hemorrhages with supratherapeutic INR in a 70-year-old patient using chamomile products (tea and skin lotion) concurrently with warfarin.

Monitor INR closely; advise patients to report all chamomile product use to their anticoagulation clinic. Avoid high-dose chamomile (more than 3 cups per day of tea or topical lotion combined) in patients on warfarin. Reduce warfarin dose cautiously if chamomile is used regularly.

Chamomile primary active constituent apigenin binds to benzodiazepine receptors on GABA-A channels, producing anxiolytic and mild sedative activity. Pharmacodynamic synergism with CNS depressants produces additive sedation, impaired psychomotor function, and cognitive depression.

Caution patients about additive sedation when combining chamomile with benzodiazepines or other sedatives. Avoid driving or operating machinery. Reduce sedative dose if combining with regular chamomile use; the interaction is more significant with concentrated chamomile extracts than culinary tea.

Preliminary studies suggest chamomile may decrease the efficacy of oral contraceptives. Chamomile inhibits CYP3A4, CYP1A2, and CYP2C9 in vitro, all of which participate in estrogen and progestogen metabolism. Disrupted hormonal metabolism may lead to unpredictable contraceptive reliability.

Advise women on hormonal contraception about the potential for irregular bleeding or unreliable contraceptive efficacy with regular chamomile use. Consider additional barrier contraception during periods of heavy chamomile consumption.

In vitro studies show chamomile essential oil and its major constituents (alpha-bisabolol, chamazulene) inhibit CYP1A2, CYP2C9, CYP2D6, and CYP3A4. This broad CYP inhibition may reduce the metabolism of co-administered drugs across multiple pathways, increasing plasma levels. Clinical significance appears modest at typical chamomile tea consumption, but concentrated extracts may produce meaningful pharmacokinetic interactions.

Monitor patients on narrow therapeutic index CYP substrates (theophylline, phenytoin, cyclosporine) if using chamomile extracts; plasma drug levels may increase. Concentrated chamomile supplements carry greater interaction risk than herbal teas. Obtain drug levels if toxicity is suspected.

Chamomile coumarin-type constituents inhibit platelet activity and aggregation via prostaglandin-related mechanisms similar to aspirin. Combined use with antiplatelet agents produces additive antiplatelet effect and increased risk of bleeding including GI hemorrhage, bruising, and surgical bleeding.

Avoid high-dose chamomile supplements in patients on antiplatelet therapy; monitor for unusual bruising or bleeding. Advise patients to inform cardiologists or stroke physicians about chamomile use. Discontinue chamomile before procedures.

Chamomile combined anticoagulant (coumarin derivatives), antiplatelet, and CNS sedative properties may potentiate anesthetic agents and increase perioperative bleeding risk. CYP3A4 inhibition may also affect clearance of anesthetics metabolized by CYP3A4 (midazolam, fentanyl). Significant systemic absorption from topical chamomile products is documented in clinical cases.

Discontinue chamomile supplements and high-dose chamomile tea at least 2 weeks before elective surgery. Inform anesthesiologist of regular chamomile use including topical products, as skin lotion was implicated in a clinical hemorrhage case.

Chamomile bisabolol has antifungal properties that may have additive effects with azole antifungals. More relevant is the potential for chamomile flavonoids to inhibit CYP3A4, which is responsible for azole metabolism, though clinical data are limited.

Use caution with concurrent administration of chamomile and azole antifungals. Monitor for excessive antifungal effects or toxicity. This interaction is primarily theoretical at typical therapeutic doses of chamomile.

Chamomile extract has demonstrated mild antihypertensive and vasodilatory effects in animal models. Apigenin modulates calcium channels and has mild relaxing effects on vascular smooth muscle. Co-administration with antihypertensives may produce modest additive blood pressure lowering.

Monitor blood pressure periodically in patients on antihypertensives who use chamomile. Risk is low at typical chamomile tea consumption levels. Higher-dose extracts warrant more caution.

Chamomile contains coumarin and flavonoid constituents that may inhibit CYP3A4 activity. In vitro studies suggest apigenin, bisabolol, and chamomile extract can inhibit CYP3A4-mediated metabolism, potentially increasing plasma concentrations of narrow-therapeutic-index CYP3A4 substrates like tacrolimus and cyclosporine.

Monitor tacrolimus and cyclosporine trough levels closely in transplant patients using chamomile supplements. Adjust immunosuppressant doses as needed based on therapeutic drug monitoring. High-dose chamomile extracts (not tea preparations) are of greater concern.