Oral Estradiol and Cannabis Interaction Profile: What You Need to Know

What does the oral estradiol label say about interactions?

The oral estradiol tablet label states that estrogens are metabolized partly by cytochrome P450 3A4 (CYP3A4). Inducers such as St. John's wort, phenobarbital, carbamazepine and rifampin may reduce plasma concentrations of estrogens, possibly lowering the therapeutic effect or changing the uterine bleeding pattern. Inhibitors such as erythromycin, clarithromycin, ketoconazole, itraconazole, ritonavir and grapefruit juice may increase plasma concentrations of estrogens and may result in side effects [1].

Cannabis, THC and CBD are not named in that section of the label.

Does cannabis affect those enzymes?

A review of medicinal cannabis drug interactions concluded that cannabinoids can produce bidirectional effects with other drugs through membrane transporters and metabolizing enzymes, including cytochrome P450 and UDP-glucuronosyltransferases, and that few data have been provided on interactions with prescription medications [2]. That is a general statement about cannabinoids, not a measurement of what cannabis does to oral estradiol.

What do human studies of THC and estradiol show?

In a 2023 trial, 60 healthy women who used cannabis occasionally received oral THC 7.5 mg, THC 15 mg or placebo, either in the early follicular phase (lower natural estradiol) or the late follicular phase (higher natural estradiol). THC impaired inhibitory control, and the impairment was not related to estradiol levels [3]. The women were not taking estradiol tablets, and the trial did not measure whether THC changes estradiol clearance.

What symptoms does the estradiol label list?

The oral estradiol label lists nausea, vomiting, abdominal cramps, bloating, breast tenderness, headache, changes in vaginal bleeding, edema and mood changes among reactions reported with estrogen therapy, without giving rates [1]. The Climara patch label, a different product, reports rates from its own trials: nausea occurred in 1% to 6% of patch users across doses versus 3% of placebo users [4].

Cannabinoids suppress nausea and vomiting in animal studies, and CBD does so within a limited dose range [5]. That is an overlap with a symptom the estradiol label lists; it is not a measurement of estradiol clearance.

Bottom line

The label's CYP3A4 list does not include cannabis, and the cannabis interaction review is a general one that does not give estradiol data [1][2]. Whether cannabis changes oral estradiol exposure has not been measured.