Cephalexin: adverse event reports filed with FDA

5,647

reports as suspect product

0% of all reports · about 251 a year

472

reports, 12 months to June 2026

581 in the 12 months before

70.6%

marked serious by the reporter

89.1% across the class

6%

record death among outcomes, as reported

336 reports · not verified by FDA

Reports by month, five years

Reports by the month FDA received them. FDA releases FAERS data quarterly, so the newest months are incomplete and grow in later releases.

By year received

2026 covers reports received through June 2026 only.

Reactions recorded in the reports

share of Cephalexin reports recording the termmedian drug in cephalosporin antibacterial

1. Rashskin rash11.9%671
2. Drug hypersensitivityan allergic-type reaction to a medicine11.4%642
3. Diarrhoealoose or frequent stools9.1%515
4. Dyspnoeashortness of breath8.1%456
5. Drug ineffectivethe medicine did not work as expected6.9%390
6. Pruritusitching6.6%371
7. Nauseafeeling sick6.2%351
8. Anxietyanxiety5.3%301
9. Urticariahives5.3%301
10. Malaisegeneral feeling of being unwell5.2%292
11. Vomitingbeing sick5%284
12. Headachehead pain4.5%255
13. Arthralgiajoint pain4.4%246
14. Pain in extremitypain in an arm or leg4.2%238
15. Condition aggravatedthe condition being treated got worse4.1%233
16. Dizzinesslight-headedness or unsteadiness4.1%231
17. Hypersensitivityan allergic-type reaction4%228
18. Abdominal pain upperupper stomach pain3.9%223
19. Coughcough3.8%215
20. Fatiguetiredness3.8%214
21. Wheezingwheezing3.8%214
22. Asthmaasthma3.6%204
23. Off label useused for a purpose or in a way not on the label3.6%203
24. Pyrexiafever3.5%199
25. Therapeutic product effect incomplete3.3%186
26. Abdominal painstomach or belly pain3.1%176
27. Neurological symptom3%170
28. Abdominal discomfortstomach discomfort3%169
29. Vasculitisinflammation of blood vessels3%168
30. Full blood count abnormal3%167

Top 30 of 1,030 MedDRA preferred terms recorded across these reports, with a plain-language gloss where one is available. One report can record several terms. The hollow bar is the median share across the 17 drugs in the cephalosporin antibacterial class; it describes the reports, not the patients. FDA states that adverse event reports "represent a small percentage of total usage numbers of a product", that "common products may have a higher number of adverse events due to the higher total number of people using the product", and that the data "by themselves are not an indicator of the safety profile of the drug or biologic."

Outcomes recorded

Outcome flags as the reporter set them; a report can carry several, and "other serious" is FDA's own category for serious reports outside the named outcomes. Grey bar: all 57,006 reports in the class. FDA has not verified any outcome and states that the reports "cannot be used to estimate the incidence of these events."

Patients and reporters

Age and sex as stated in the report; the reporter's qualification is the primary source recorded by FDA. 50.5% of reports give the United States as the country of the event or reporter.

Reason for use recorded

The indication field is filled in by the reporter and is often blank; shares are of all 5,647 reports.

Drugs most often listed in the same reports

Other products listed in reports where Cephalexin is a suspect product, whatever their own role. Co-listing means the two were recorded together; it says nothing about either product's part in the event. Only the 2,500 most-reported names are counted here.

In context

Shares are of reports, not of patients treated. The number of people taking a product is not in the data, so none of these figures is a rate, and differences between columns reflect who takes a product, who reports and how long it has been sold. FDA states that adverse event reports "represent a small percentage of total usage numbers of a product", that "common products may have a higher number of adverse events due to the higher total number of people using the product", and that the data "by themselves are not an indicator of the safety profile of the drug or biologic."

Other drugs in the cephalosporin antibacterial class

Ordered by report count for navigation only. FDA states that adverse event reports "represent a small percentage of total usage numbers of a product", that "common products may have a higher number of adverse events due to the higher total number of people using the product", and that the data "by themselves are not an indicator of the safety profile of the drug or biologic." A brand and its generic are separate rows because reporters name them separately.

Where this comes from. Counts are built from the openFDA Drug Adverse Event (FAERS) bulk export released 28 Sep 2026, which holds reports FDA received through 30 Jun 2026. Drug names are as reported, resolved to the brand or generic name on the FDA label where openFDA's harmonisation matched them; classes are the pharmacologic class (EPC) from the label and the National Drug Code Directory of 17 Sep 2026. A report counts here when it lists Cephalexin as a suspect or interacting product; reports listing it only as a concomitant medication (17,572) are excluded. No report narrative, lot number, patient detail or reporter identity is published. See the methodology and sources; FDA's record is authoritative, and corrections are handled within five working days.