Amoxicillin
Severe
Textbook-cited
Reduced contraceptive efficacy; risk of unintended pregnancy
Advise use of alternative or additional contraception during antibiotic course
Source: KDT 7e · p948
Drug reference
Ethinylestradiol
Estrogen · Oral Contraceptive
EstrogenOral Contraceptive
CDSCO approvedSchedule H
EXCRETION
—
not curated
INTERACTIONS
12 major
SEVERE in our sources
PREGNANCY
Manufacturer advises avoid unless
FDA category + note
Top interactionssee all 12 →
- AmoxicillinSevereTextbook-citedKDT 7e · p948
- AmpicillinSevereTextbook-citedKDT 7e · p948
- CarbamazepineSevereTextbook-citedKDT 7e · p949
- CotrimoxazoleSevereTextbook-citedKDT 7e · p948
Mechanism
Ethinylestradiol is a synthetic estrogen with a 17α-ethinyl substitution that protects against first-pass hepatic metabolism, making it 20-fold more potent orally than natural estradiol. It binds to estrogen receptors ERα and ERβ, acting as a nuclear transcription factor that modulates gene expression in reproductive tissues, bone, liver, and the cardiovascular system. At contraceptive doses, it suppresses FSH secretion via hypothalamic-pituitary negative feedback, inhibiting follicular development and ovulation.
Indications
Menopausal syndromeCombined oral contraceptives
Dosing
- Adult
- Missed doses Manufacturer advises if a dose is more than 18 hours late, the missed dose should not be taken and the next dose should be taken at the normal time. If vomiting occurs within 1 hour of taking a dose, a replacement dose should be taken. l CAUTIONS l INTERACTIONS l MEDICINAL FORMS No licensed medicines listed.…
Pharmacokinetics
Half-life
12–24 hours
Metabolism
Ethinylestradiol is a component of combined oral contraceptive pills and its metabolism can be increased by enzyme inducers like rifampin.
Pregnancy & lactation
Pregnancy
Manufacturer advises avoid unless
Drug interactions
Ampicillin
Severe
Textbook-cited
Reduced contraceptive efficacy; risk of unintended pregnancy
Advise use of alternative or additional contraception during antibiotic course
Source: KDT 7e · p948
Carbamazepine
Severe
Textbook-cited
Contraceptive failure
Advise alternative or higher-dose contraception
Source: KDT 7e · p949
Cotrimoxazole
Severe
Textbook-cited
Contraceptive failure
Advise alternative contraception
Source: KDT 7e · p948
Doxycycline
Severe
Textbook-cited
Contraceptive failure
Advise alternative contraception
Source: KDT 7e · p949
Minocycline
Severe
Textbook-cited
Contraceptive failure
Advise alternative contraception
Source: KDT 7e · p949
Phenobarbital
Severe
Textbook-cited
Contraceptive failure
Advise alternative or higher-dose contraception
Source: KDT 7e · p949
Phenytoin
Severe
Textbook-cited
Contraceptive failure
Advise alternative or higher-dose contraception
Source: KDT 7e · p949
Rifampicin
Severe
Textbook-cited
Contraceptive failure
Advise alternative or higher-dose contraception
Source: KDT 7e · p949
Sulfonamides
Severe
Textbook-cited
Contraceptive failure
Advise alternative contraception
Source: KDT 7e · p948
Tetracycline
Severe
Textbook-cited
Contraceptive failure
Advise alternative contraception
Source: KDT 7e · p949
Rifampin
Severe
Textbook
Decreased effectiveness of oral contraception, leading to contraceptive failure and unwanted pregnancy.
Patients should use alternative or additional contraceptive methods while on rifampin and for a period after discontinuation.
Source: KDT 7e · p36
Related guidelines
Empirical antimicrobial use in common syndromes
ICMR · Infectious Diseases · 2019
Acute coronary syndrome in chronic kidney disease
CSI · Cardiology · 2020
Sjögren's syndrome
EULAR · Rheumatology · 2025
Primary PCI for acute coronary syndrome
ESC · Cardiology · 2026
Irritable bowel syndrome
ISG · Gastroenterology · 2023
Other Estrogen drugs
Ask House about Ethinylestradiol
Continue into a citation-backed clinical answer with the drug context already attached.
Sources: KD Tripathi 7e, BNF·Verified: 2026-05-13 · House clinical team