Drug General Information (ID: DDI5TU4689)
Drug Name			Estradiol		Drug Info		Benzylpenicillin (potassium)		Drug Info
Drug Type		Small molecule				Small molecule
Therapeutic Class		Estrogens				Antibiotics
Structure

Mechanism of Estradiol-Benzylpenicillin (potassium) Interaction (Severity Level: Moderate)
Attenuated pharmacological effects (Unspecific) Click to Show/Hide Mechanism Graph
Drug Name		Estradiol				Benzylpenicillin (potassium)
Mechanism		Hormonal contraceptives				Reduce the therapeutic efficacy of estrogen-containing oral contraceptives
Key Mechanism Factor 1
		Factor Name		Pharmacodynamics
		Factor Description		Reduced pharmacological effects leading to insufficient efficacy and/or treatment failure.
Mechanism Description		Attenuated pharmacological effects of  Estradiol when combined with Benzylpenicillin (potassium)

Recommended Action
Management		Until further data are available, women using oral contraceptives should be advised of the risk of breakthrough bleeding and unintended pregnancy during concomitant antimicrobial therapy. alternative or additional methods of birth control should be considered during and for at least one week beyond the last dose of short-term antimicrobial therapy, and for at least the initial weeks of long-term antimicrobial therapy when risk may be the greatest.

References
1	Back DJ, Breckenridge AM, Crawford FE, MacIver M, Orne ML, Rowe PH "Interindividual variation and drug interactions with hormonal steroid contraceptives." Drugs 21 (1981): 46-61. [PMID: 7009137]
2	Barnett ML "Inhibition of oral contraceptive effectiveness by concurrent antibiotic administration." J Periodontol 56 (1985): 18-20. [PMID: 3882930]
3	King VJ "OC failure rates and oral antibiotics." J Fam Pract 45 (1997): 104-5. [PMID: 9267366]