Cefdinir and Norgestimate: Interaction Details
AI-assisted, pharmacist-reviewed · Source data updated Aug 8, 2026 · Sources: FDA labeling, DDInter 2.0, cited literature
Norgestimate
No brand names on recordCefdinir
How we grade severity & evidence
Severity levels
- Contraindicated: These should generally not be used together.
- Major: Potentially serious — often needs a change or close monitoring.
- Moderate: Can be significant — usually manageable with monitoring.
- Minor: Usually limited clinical impact.
Evidence grades
- Established: Well documented — supported by controlled studies or strong clinical data.
- Probable: Good supporting evidence, though not definitively proven.
- Suspected: Some evidence suggests this interaction, but it is not well established.
- Possible: Limited or conflicting evidence; the interaction may occur.
- Theoretical: Predicted from the drugs' pharmacology; not yet confirmed in people.
Ratings come from the documented interaction literature and are reviewed by a pharmacist. They describe the documented risk of the combination, not what will necessarily happen to you — your dose, timing, and health picture all matter.
What happens
Decreased contraceptive effectiveness
Interaction Deep Dive
Contraceptive effectiveness may be reduced when oral contraceptives are coadministered with antibiotics. The mechanism of interaction is thought that cephalosporins may alter intestinal flora which, in turn, may alter the enterohepatic circulation of combination contraceptives, which could result in unintended pregnancies and menstrual changes23. However, in a large retrospective chart review, there was no significant difference in oral contraceptive (OC) failure rates among women who received OC with or without concomitant antibiotics, including cephalosporins; and the OC failure rate in both groups did not exceed a typical contraceptive failure rate of 1% to 3%. If at any time, a 1% to 3% contraceptive failure rate is unacceptable to the patient, an additional form of contraception should be recommended 1.
Why it happens (mechanism)
Alteration in gut flora, leading to decreased estrogen reabsorption
Literature reports
1 report — tap to read
a) There was no significant difference in oral contraceptive (OC) failure rates among women who received OC with or without concomitant antibiotics, including cephalosporins; and the OC failure rate in both groups did not exceed a typical contraceptive failure rate of 1% to 3% in a retrospective chart review and follow-up survey. Of 356 women who received antibiotics and OC concurrently over 311.2 woman-years, 5 pregnancies occurred yielding a rate of 1.6 pregnancies per 100 woman-years or a 1.6%/year failure rate. Of 425 control patients who received OC without antibiotics for 1244.9 woman-years, 12 pregnancies occurred yielding a rate of 0.96 pregnancies per 100 woman-years or 0.96%/year failure rate. The difference in failure rate between these groups was not significant (95% CI on the difference, -0.81 to 2.1; p=0.4) and ruled out a substantial difference (greater than 2.1% per year). The women in the control group consisted of 263 women who received OC but did not concomitantly use OC with antibiotics and 162 OC users who never concomitantly used antibiotics. Among women who never concomitantly used antibiotics (n=162) over 551.2 woman-years, 7 pregnancies occurred, yielding a rate of 1.3 pregnancies per 100 woman-years or 1.3%/year failure rate 1.
Common questions
Can I take Cefdinir and Norgestimate together?
Decreased contraceptive effectiveness Always confirm with your pharmacist or prescriber before making any change.
How serious is the Cefdinir and Norgestimate interaction?
It is rated major. Potentially serious — often needs a change or close monitoring.
How quickly could this interaction happen?
The documented onset is "delayed". Effects tend to build up gradually over days to weeks.
How strong is the evidence for this interaction?
The evidence is graded "theoretical". Predicted from the drugs' pharmacology; not yet confirmed in people.
Questions for your pharmacist
- Does my dose of Cefdinir or Norgestimate need adjusting while I take them together?
- What symptoms should prompt me to call you or my prescriber right away?
- Does the timing of my doses matter for this combination?
- Is there a safer alternative to one of these medications for me?
References (3)
- Helms SE, Bredle DL, Zajic J, et al: Oral contraceptive failure rates and oral antibiotics. J Am Acad Dermatol 1997; 36(5 Pt 1):705-710. PubMed
- Back DJ, Breckenridge AM, Crawford FE, et al: Interindividual variation and drug interactions with hormonal steroid contraceptives. Drugs 1981; 21:46-61. DOI
- Bainton R: Interaction between antibiotic therapy and contraceptive medication. Oral Surg Oral Med Oral Pathol 1986; 61:453-455. PubMed
Keep reading about Norgestimate
Keep reading about Cefdinir
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