Last reviewed 2026-04-22 · How we verify

13C-Methacetin

13C-Methacetin is a stable isotope-labeled tracer used to assess hepatic metabolic function and liver synthetic capacity.

13C-Methacetin is a stable isotope-labeled tracer used to assess hepatic metabolic function and liver synthetic capacity. Used for Assessment of hepatic metabolic function in patients with liver disease, Non-invasive evaluation of liver synthetic capacity and cirrhosis severity.

At a glance

Mechanism of action

13C-Methacetin is a non-invasive diagnostic agent that measures liver function by tracking the metabolism of a methyl-labeled acetaminophen derivative. After oral administration, the drug is metabolized by hepatic cytochrome P450 enzymes, and the resulting 13C-labeled carbon dioxide is exhaled and measured in breath samples, providing a quantitative assessment of hepatic metabolic capacity without requiring blood draws or imaging.

Approved indications

• Assessment of hepatic metabolic function in patients with liver disease
• Non-invasive evaluation of liver synthetic capacity and cirrhosis severity

Common side effects

No common side effects on file.

Key clinical trials

• Chronic Mesenteric Ischemia Breath Testing (NA)
• Methacetin Breath Test in Patients With Liver Disease Secondary to Heart Disease (NA)
• BreathID 13C-Methacetin Breath Test for Detecting Cirrhosis (PHASE3)
• Assessing Portal Hypertension With Methacetin Breath Test (NA)
• BREATHID Octanoate Breath Test With or Without Methacetin Breath Test for Correlation With Biopsy in NASH (PHASE2)
• Prediction Value of the BreathID 13C-Methacetin Breath Test for Hepatic Decompensation
• Companion Protocol for ¹³C-Methacetin Breath Tests in BMS: NCT03486899, NCT03486912 Referenced Trials
• 13C-Methacetin Breath Test for the Prediction of Outcome in in ALI or ALF (PHASE2, PHASE3)

Primary sources

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