Fosphenytoin: adverse event reports filed with FDA

947

reports as suspect product

0% of all reports · about 48 a year

64

reports, 12 months to June 2026

132 in the 12 months before

91.1%

marked serious by the reporter

78.1% across the class

12.1%

record death among outcomes, as reported

115 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 Fosphenytoin reports recording the termmedian drug in anti-epileptic agent

1. Drug ineffectivethe medicine did not work as expected34.1%323
2. Off label useused for a purpose or in a way not on the label13.1%124
3. Status epilepticus8.2%78
4. Multiple-drug resistance8%76
5. Drug interactionan interaction between medicines5.8%55
6. Seizurea fit or convulsion5.5%52
7. Cardiac arrestthe heart stopped4.5%43
8. Drug ineffective for unapproved indication4.2%40
9. Hypotensionlow blood pressure3.9%37
10. Toxicity to various agentspoisoning or toxic effect of one or more substances3.5%33
11. Treatment failurethe treatment did not work3.3%31
12. Bradycardiaslow heart rate2.5%24
13. Haemodynamic instability2.3%22
14. Drug reaction with eosinophilia and systemic symptomsDRESS, a severe reaction with rash, fever and organ involvement2.2%21
15. Epilepsy2.2%21
16. Product use in unapproved indicationused for a purpose not on the label2.2%21
17. Tachycardiafast heart rate2.2%21
18. Myocardial depression2.1%20
19. Therapy non-responderthe treatment did not work2%19
20. Atrioventricular block1.6%15
21. Exposure during pregnancythe medicine was taken during pregnancy1.5%14
22. Laryngeal stenosis1.5%14
23. Sedationdrowsiness from a medicine1.5%14
24. Stevens-Johnson syndromea severe skin and mucous-membrane reaction1.5%14
25. Generalised tonic-clonic seizure1.4%13
26. Respiratory acidosis1.4%13
27. Respiratory failurethe lungs could not supply enough oxygen1.4%13
28. Hypocalcaemialow blood calcium1.3%12
29. Ventricular dysfunction1.3%12
30. Vitamin D deficiencylow vitamin D1.3%12

Top 30 of 230 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 23 drugs in the anti-epileptic agent 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 269,757 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. 75.8% 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 947 reports.

Drugs most often listed in the same reports

Other products listed in reports where Fosphenytoin 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 anti-epileptic agent 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 Fosphenytoin as a suspect or interacting product; reports listing it only as a concomitant medication (618) 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.