Possible Drug Interactions With Chamomile

Though natural, herbs can still pose medication interactions. There have actually been very few reported interactions between chamomile and over-the-counter or prescription drugs, but the most significant ones are related to use of the herb with Coumadin (warfarin)—a common blood thinner—and cyclosporine—a drug used to prevent rejection after organ transplantation. There are also theoretical interactions that could occur due to the biochemistry of chamomile.

Used by some for insomnia and settling the stomach, among other issues, chamomile is available in teas and in supplement form.

As with all herbal supplements, chamomile hasn't been tested for safety in pregnant women, nursing mothers, children, and those with medical conditions or who are taking medications. If you're considering the use of chamomile, talk with your doctor first.

Anticoagulants

Coumadin (warfarin) is derived from coumarin, a compound commonly found in plants such as chamomile that can have anticoagulant properties depending on its chemical structure. This drug is commonly prescribed as a blood thinner to prevent clots that may lead to a heart attack, stroke, or deep venous thrombosis (DVT).

Taking too much warfarin on its own can result in bleeding, but there is potential for the same thing to occur when the correct dosage is adhered to and high concentrations of a coumarin-containing herb or product—like chamomile—is consumed as well. While there is no evidence of a drug-herb interaction between warfarin and chamomile, there has been one documented clinical case of internal bleeding in a person consuming chamomile tea and using chamomile lotion in addition to warfarin.

With this concern, talk to your doctor before taking herbal supplements if you are taking other medications aimed at blood-thinning or preventing blood clots. These medications include aspirin and platelet inhibitors such as Ticlid (ticlopidine) and Plavix (clopidogrel).

There are many other herbs that carry warnings about interactions with anticoagulants, including Ginkgo biloba, garlic, and ginseng.

Health Benefits of Chamomile
Illustration by Emily Roberts, Verywell

Cyclosporine

Cyclosporine is used by transplant recipients to prevent rejection. It has a narrow therapeutic window, meaning that the amount taken needs to be precise in order to get the desired effects.

Cyclosporine is broken down in the liver by the CYP3A4 enzyme. Chamomile inhibits the function of this enzyme.

There has been a documented case in which the levels of cyclosporine were raised when a person taking the drug was drinking chamomile tea regularly. When they stopped the tea, their cyclosporine level dropped.

As a result of this and other reports, healthcare providers advise against consuming chamomile while taking anti-rejection drugs.

Theoretical Interactions

Chamomile has compounds that inhibit drug-metabolizing enzymes of the human cytochrome P450 family (CYP1A2, CYP2C9, CYP2D6, and CYP3A4). As a result, blood levels for various drugs may be higher than expected when chamomile is consumed.

There have not been documented reports of this occurring, other than for warfarin and cyclosporine. But it is theoretically possible to occur with use of the following drugs, which are metabolized by CYP1A2, in combination with chamomile:

Several studies have looked into using chamomile for blood glucose control in people with diabetes. Some have found effects in lowering insulin levels.

As such, it is best to discuss chamomile with your healthcare provider if you have diabetes and are taking insulin.

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