Colesevelam
Moderate
Textbook
Altered plasma levels and efficacy of ethinyl estradiol, potentially reducing contraceptive effect.
Source: G&G 14e · p1041
Drug reference
ethinyl estradiol
Synthetic Estrogen · Contraceptive
Synthetic EstrogenContraceptive
CDSCO approved
EXCRETION
—
not curated
INTERACTIONS
—
none in our sources
PREGNANCY
—
not curated
Mechanism
Not yet extracted
Indications
hormonal contraceptiontransdermal contraceptionintravaginal contraception
Dosing
- Adult
- 20 to 35 μg/day (in oral contraceptives)
Pharmacokinetics
Half-life
13 to 27 h (elimination-phase)
Protein binding
extensively to serum albumin but not SHBG
Metabolism
primarily via 2-hydroxylation and subsequent formation of 2- and 3-methyl ethers (less hepatic metabolism than estradiol)
Contraindications
- thromboembolic disease
- cerebrovascular disease
- myocardial infarction
- coronary artery disease
- congenital hyperlipidemia
- known or suspected carcinoma of the breast
- carcinoma of the female reproductive tract
- abnormal undiagnosed vaginal bleeding
- known or suspected pregnancy
- liver tumors
- impaired liver function
- women more than 35 years of age who smoke heavily
Side effects
Serious
- increased risk of venous thromboembolism (with transdermal patch)
- increased coagulation factors
Drug interactions
Ritonavir
Moderate
Textbook
Ritonavir reduces the AUC of ethinyl estradiol by 40%.
Alternative forms of contraception should be used.
Source: G&G 14e · p1245-1266
Deflazacort
Moderate
Database
Increased systemic exposure to deflazacort, leading to an increased risk of corticosteroid-related adverse effects.
Monitor for increased corticosteroid effects. A deflazacort dose adjustment may be necessary.
Ursodeoxycholic Acid
Moderate
Database
Reduced efficacy of ursodeoxycholic acid, especially for gallstone dissolution.
Avoid concomitant use if possible, particularly when ursodeoxycholic acid is used for gallstone dissolution. Consider alternative contraception.
Related guidelines
Ask House about ethinyl estradiol
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Sources: Goodman & Gilman 14e·Verified: 2026-05-10 · House clinical team