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
2 additional unreviewed or low-confidence interactions hidden because their provenance or source detail is insufficient.
Related guidelines
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Textbook-sourced·Sources: Goodman & Gilman 14e·Updated: 2026-05-10