Pharmacologic class (EPC) · 2 drug pages

l-Triiodothyronine: adverse event reports filed with FDA

2,653 reports list a drug in this class as a suspect or interacting product, 2004–2026.

Read first · FDA's statement on these data

Adverse event reports submitted to FDA do not undergo extensive validation or verification. Therefore, a causal relationship cannot be established between product and reactions listed in a report. While a suspected relationship may exist, it is not medically validated and should not be the sole source of information for clinical decision making or other assumptions about the safety or efficacy of a product. Additionally, it is important to remember that adverse event reports represent a small percentage of total usage numbers of a product. Common products may have a higher number of adverse events due to the higher total number of people using the product. openFDA, FDA

FDA adds: "There is no certainty that the reported event (adverse event or medication error) was actually due to the product. FDA does not require that a causal relationship between a product and event be proven, and reports do not always contain enough detail to properly evaluate an event." The information in these reports "cannot be used to estimate the incidence of these events."

Do not rely on openFDA to make decisions regarding medical care. While we make every effort to ensure that data is accurate, you should assume all results are unvalidated.

Not medical advice. This site counts what was reported to FDA. Questions about a medicine or device belong with a pharmacist or clinician.

2,653
reports across the class: 0% of all reports; 96
reports, 12 months to June 2026: 70 in the 12 months before; 31.7%
marked serious by the reporter: 57.4% across all reports; 2
drugs with a page: brand and generic names counted separately

l-Triiodothyronine is a pharmacologic class (an FDA Established Pharmacologic Class) with 2 drug pages on this site. Together those drugs are listed as a suspect or interacting product in 2,653 adverse event reports received by FDA, 0% of the database, from February 2004 to June 2026.

96 reports arrived in the 12 months to June 2026, up 37% from 70 in the 12 months before. FDA releases FAERS data quarterly, so the newest months are incomplete and grow in later releases. 31.7% of the class's reports are marked serious, 0.5% record death among the outcomes and 14.4% record hospitalisation, as reported.

Across the class the reactions recorded most often are drug ineffective (19.6%), headache (13.2%) and hypothyroidism (11.8%). The class median share shown beside each term is the middle value across the member drugs; it is the comparison used on every drug page in this class.

The members table is 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."

Drugs in the class

Drug	Name type	Reports	Latest 12 months	Marked serious	Top term recorded
Liothyronine sodium	generic	1,423	68	37.6%	Drug ineffective
CytomelLiothyronine sodium	brand	1,230	28	25%	Drug ineffective

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."

Reports by month, five years

FDA releases FAERS data quarterly, so the newest months are incomplete and grow in later releases.

Reactions recorded across the class

share of class reports recording the termmedian drug in the class

Drug ineffectivethe medicine did not work as expected19.6%519
Headachehead pain13.2%350
Hypothyroidismunderactive thyroid11.8%312
Therapeutic product effect incomplete10.4%277
Hypertensionhigh blood pressure10.3%272
Cardiac disorder9.5%253
Dyspnoeashortness of breath9.5%253
Burning sensationa burning feeling9.3%247
Asthmaasthma9.3%246
Blood test abnormal9%238
Fibromyalgia8.9%236
Gastrooesophageal reflux diseaseacid reflux8.9%236
Polycystic ovaries8.8%234
Sensitisation8.8%234
Carpal tunnel syndrome8.8%233
Rhinitis allergic8.8%233
Sleep apnoea syndromepauses in breathing during sleep8.7%232
Fatiguetiredness8.6%229
Sleep disorder due to a general medical condition8.4%223
Loss of personal independence in daily activities7.7%205
Renal disorder7.5%199
Malaisegeneral feeling of being unwell7.4%196
Ejection fraction7.4%195
Feeling abnormalfeeling odd or not right6.9%183
Wheezingwheezing6.7%179

Solid bar: share of all class reports. Hollow bar: the median share across the 2 member drugs, the reference used on each member's page. One report can record several terms.

Outcomes, patients and reporters

Outcomes recorded

Death0.5%14

Life-threatening1.2%31

Hospitalisation (initial or prolonged)14.4%382

Disability0.9%24

Congenital anomaly0.1%3

Other serious26.1%693

Not serious68.3%1,811

Patient age

Under 20%1

2 to 110%0

12 to 170.3%7

18 to 447.4%195

45 to 6427.4%728

65 to 749.3%248

75 and over3.6%96

Age not given51.9%1,378

Who reported

Physician8.5%225

Pharmacist4.1%109

Other health professional7.7%203

Lawyer0.1%2

Consumer or non-health professional77.9%2,068

Not given1.7%46

Grey bar: all 20,646,523 reports in the database. Outcome flags are as the reporter set them and are not verified by FDA.

Questions about l-Triiodothyronine reports

Which drugs are in the l-Triiodothyronine class on this site?

Liothyronine sodium and Cytomel. Class membership comes from the pharmacologic class (EPC) on the drug's FDA label.

How many reports does the class have?

2,653 reports through June 2026, 96 of them in the latest 12 months. A report listing two drugs of the class counts once for each.

What reactions are recorded most often?

drug ineffective (19.6%), headache (13.2%), hypothyroidism (11.8%), therapeutic product effect incomplete (10.4%) and hypertension (10.3%).

Can the members table be used to rank the drugs?

No. 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." Drugs differ in how many people take them, in the conditions they treat, in time on the market and in how diligently reports are collected.

How do I report an adverse event?

Through FDA MedWatch (Form FDA 3500, or 1-800-FDA-1088) or to the manufacturer. See the guide on how to report.

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 class is the Established Pharmacologic Class most often attached to a drug's reports by openFDA's label harmonisation, or from the NDC Directory where reports carry none. 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.

Drug data (FAERS) through 30 Jun 2026; device data (MAUDE) through 31 Aug 2026. Not medical advice.