Trazodone Liver Function Impact: What the Evidence Actually Shows

What the Trazodone Label Says About the Liver

The prescribing information lists four hepatobiliary reactions under postmarketing experience: cholestasis, jaundice, hyperbilirubinemia and liver enzyme alterations [1]. The label says reactions in that section are reported voluntarily from a population of uncertain size, so a frequency cannot always be estimated and a causal relationship cannot always be established [1].

Liver injury is not one of the warnings the label highlights. Its warnings and precautions cover serotonin syndrome, QT prolongation and arrhythmia, orthostatic hypotension and syncope, bleeding risk, priapism, activation of mania or hypomania, cognitive and motor impairment, angle-closure glaucoma and hyponatremia [1]. The boxed warning is for suicidal thoughts and behaviors [1].

How Often Does Trazodone Cause Liver Injury?

The most useful estimate available is class-wide. A 2014 review of antidepressant-induced liver injury in the American Journal of Psychiatry reported that 0.5% to 3% of patients treated with antidepressants may develop asymptomatic mild elevation of serum aminotransferase levels [2]. The review describes antidepressant drug-induced liver injury as an infrequent event overall [2].

The same review places trazodone in the group of antidepressants associated with greater hepatotoxicity risk, alongside iproniazid, nefazodone, phenelzine, imipramine, amitriptyline, duloxetine, bupropion, tianeptine and agomelatine. It places citalopram, escitalopram, paroxetine and fluvoxamine among those with the least potential for hepatotoxicity [2].

What Kind of Liver Injury Does It Cause?

The review describes antidepressant liver injury as idiosyncratic and unpredictable, generally unrelated to drug dosage, with onset usually between several days and 6 months after starting treatment [2]. The underlying lesion is often hepatocellular and less frequently cholestatic or mixed [2]. Life-threatening cases have been described, including fulminant liver failure or death [2].

The American College of Gastroenterology's 2021 clinical guideline makes two general points about idiosyncratic drug-induced liver injury. It is a diagnosis of exclusion, so other causes of liver disease should be assessed first [4]. And mortality can reach 10% when hepatocellular jaundice is present, with progressive jaundice, with or without coagulopathy, a reason for referral to a tertiary care center [4].

Metabolism and Exposure

Trazodone is extensively metabolized, with less than 1% of an oral dose excreted unchanged in urine [1]. CYP3A4 converts it to the active metabolite m-chlorophenylpiperazine (mCPP). In 16 human liver microsome preparations and 8 expressed enzymes, only CYP3A4 produced mCPP, and ketoconazole blocked that step [1][5].

Blocking CYP3A4 raises trazodone exposure. In a single-dose, blinded, four-way crossover study of 10 healthy volunteers, low-dose ritonavir cut apparent oral clearance of a 50 mg trazodone dose from 155 to 75 mL/min and lengthened half-life from 6.7 to 14.9 hours, with more sedation, fatigue and adverse effects [6]. The label says to consider a lower trazodone dose, based on tolerability, with a strong CYP3A4 inhibitor such as itraconazole, ketoconazole, clarithromycin or indinavir, and to consider a higher dose with a strong inducer such as rifampin or carbamazepine. It gives increased exposure and a higher risk of adverse reactions, including cardiac arrhythmias, as the concern with inhibitors [1].

Who May Be at Higher Risk

A large all-drug registry, the Drug-Induced Liver Injury Network, provides general context rather than trazodone-specific risk estimates. Among 899 patients judged to have definite, highly likely or probable drug-induced liver injury, 10% died or underwent liver transplantation and 17% had chronic injury [3]. The 89 patients with pre-existing liver disease appeared to have more severe injury, a difference that did not reach statistical significance (P=.09), and had significantly higher mortality (16% versus 5.2%, P<0.001) [3].

The antidepressant review adds older age and polypharmacy to the factors associated with antidepressant liver injury [2].

Is Liver Monitoring Required?

The trazodone label's warnings and precautions do not list liver testing [1]. The review of antidepressant hepatotoxicity identifies aminotransferase surveillance as the most useful tool for detecting liver injury [2].

What About the Low Doses Used for Sleep?

The label's only indication is major depressive disorder in adults, and it gives no insomnia dose, so sleep use is off-label [1]. A 2005 review identified 18 insomnia studies and concluded that evidence for trazodone's efficacy in insomnia was very limited, that side effects are not inconsequential, and that it was uncertain whether the risk-benefit ratio warranted its use in nondepressed patients with insomnia [7]. The antidepressant liver injury review describes that injury as generally unrelated to dose, so a low dose is not shown to be safer for the liver [2].