Rezdiffra (Resmetirom) and Trazodone Interaction

Why This Combination Comes Up in Clinical Practice

Patients prescribed Rezdiffra (resmetirom) for metabolic dysfunction-associated steatohepatitis (MASH) frequently carry comorbid depression, anxiety, or insomnia. Trazodone remains one of the most prescribed sedating antidepressants in the United States, with over 25 million dispensed prescriptions annually according to IQVIA data. The overlap between MASH populations and mood or sleep disorders is substantial: a 2021 meta-analysis of 11 observational studies (N = 285,964) found that patients with non-alcoholic fatty liver disease had a 1.6-fold increased odds of depression compared to controls 1. Clinicians managing both conditions need clear, evidence-based guidance on whether resmetirom and trazodone can coexist safely in the same regimen.

The FDA approved resmetirom in March 2024 under the brand name Rezdiffra for adults with non-cirrhotic MASH and moderate-to-advanced liver fibrosis (stages F2 and F3) 2. Because the drug is relatively new, formal drug-drug interaction studies with trazodone have not been published. The guidance below synthesizes the known pharmacology of each agent, the Rezdiffra prescribing information, and established CYP-mediated interaction principles.

Pharmacokinetic Overlap: The CYP3A4 Connection

Both resmetirom and trazodone are substrates of cytochrome P450 3A4 (CYP3A4), meaning they compete for the same hepatic enzyme during first-pass and systemic metabolism. This is the primary pharmacokinetic concern.

Resmetirom undergoes oxidative metabolism predominantly via CYP3A4, with a minor contribution from CYP2C8 2. The Rezdiffra label states that co-administration with strong CYP3A4 inhibitors (such as itraconazole) increased resmetirom area under the curve (AUC) by approximately 140%. Trazodone is not a strong CYP3A4 inhibitor. It is classified as a minor substrate and weak inhibitor of CYP3A4 3. The practical result: trazodone is unlikely to raise resmetirom plasma concentrations to a clinically dangerous degree.

Going the other direction, resmetirom does not appear to inhibit or induce CYP3A4 at therapeutic concentrations based on in-vitro data reported in the FDA clinical pharmacology review 2. Trazodone's primary active metabolite, meta-chlorophenylpiperazine (mCPP), is also formed via CYP3A4. A mild elevation in mCPP levels could theoretically increase nausea or anxiety, but this effect has only been documented with strong CYP3A4 inhibitors like ritonavir, not with weak substrates 4.

In short, the pharmacokinetic interaction between these two drugs at standard doses is expected to be minimal. No dose reduction of either agent is mandated by the current labeling when they are combined.

Pharmacodynamic Concerns: Sedation and CNS Depression

The more relevant clinical issue is pharmacodynamic. Trazodone's mechanism of action involves antagonism of serotonin 5-HT2A receptors, histamine H1 receptors, and alpha-1 adrenergic receptors, all of which produce sedation 3. Resmetirom itself lists fatigue and dizziness as reported adverse events. In the MAESTRO-NASH trial (N = 966), dizziness occurred in 6.3% of patients receiving resmetirom 100 mg versus 3.7% on placebo 5.

When two drugs that each independently cause dizziness or fatigue are combined, the result can be additive CNS depression. Patients may experience:

• Excessive daytime drowsiness, particularly in the first two weeks of co-administration
• Impaired coordination or slowed reaction time
• Orthostatic hypotension (trazodone's alpha-1 blockade is the primary driver here)

Dr. Zobair Younossi, a hepatologist and lead investigator in MASH outcomes research, has noted: "Patients with MASH often take multiple medications for metabolic comorbidities. Clinicians should review the entire medication list for additive sedation risk before adding a new agent" 6.

The risk is manageable. It does not typically require avoiding the combination. But it does require counseling and, in some cases, dose timing adjustments.

QT Prolongation: Assessing the Cardiac Signal

Trazodone carries an FDA label warning for QT prolongation and has been associated with torsades de pointes in post-marketing reports, particularly at doses exceeding 300 mg daily or in patients with pre-existing cardiac disease 3. Resmetirom, by contrast, showed no clinically meaningful effect on QTc interval in a thorough QT study at doses up to 600 mg (six times the maximum recommended dose), with an upper bound of the 90% confidence interval for the largest time-matched mean difference of 4.8 ms 2.

This asymmetry is reassuring. Resmetirom does not compound trazodone's QT liability through a pharmacodynamic mechanism. The scenario that warrants caution is one where a strong CYP3A4 inhibitor is added to the regimen (such as clarithromycin or ketoconazole), raising both trazodone and resmetirom levels simultaneously. In that three-drug scenario, both sedation and QT risk could escalate meaningfully.

For the two-drug combination alone, routine electrocardiogram (ECG) monitoring is not required in patients without baseline QT prolongation, electrolyte abnormalities, or concomitant use of other QT-prolonging agents 7.

Liver Safety Considerations in MASH Patients

Resmetirom is specifically indicated for patients with liver fibrosis, a population that may have altered drug metabolism at baseline. The Rezdiffra prescribing information recommends checking ALT, AST, and total bilirubin before initiation and periodically thereafter 2. Resmetirom should be discontinued if ALT or AST rises above 5 times the upper limit of normal or if signs of liver injury develop.

Trazodone has rare but documented hepatotoxic potential. The NIH LiverTox database classifies trazodone-associated liver injury as rare (estimated <1 per 100,000 users) but clinically significant when it occurs, with onset typically within the first 1 to 6 months of therapy 8.

The American Association for the Study of Liver Diseases (AASLD) 2023 practice guidance on MASLD/MASH states: "Hepatotoxic medications should be used with caution in patients with advanced fibrosis, and liver biochemistries should be monitored at regular intervals when new agents are introduced" 9.

For patients taking both drugs, a reasonable monitoring schedule includes:

• Baseline ALT, AST, and total bilirubin before starting resmetirom
• Repeat liver tests at 4 weeks, 12 weeks, and every 3 to 6 months thereafter
• Prompt re-evaluation if the patient reports new-onset fatigue, jaundice, dark urine, or right-upper-quadrant pain

Dose Timing and Practical Adjustments

No formal dose reduction is required for either drug when used together. The Rezdiffra label specifies weight-based dosing: 80 mg daily for patients weighing <100 kg and 100 mg daily for those weighing ≥100 kg, taken with food 2. Trazodone for insomnia is typically dosed at 25 to 100 mg at bedtime; for depression, doses range from 150 to 400 mg daily in divided doses.

A practical strategy to reduce peak sedation overlap: take resmetirom in the morning with breakfast and trazodone at bedtime. This separates the peak plasma concentrations (resmetirom Tmax is approximately 4 hours; trazodone Tmax is 1 to 2 hours on an empty stomach, 2 to 3 hours with food) and minimizes the window during which both drugs contribute to CNS depression simultaneously 2 3.

Patients starting trazodone while already on resmetirom should begin at the lower end of the trazodone dose range (25 mg at bedtime for insomnia, 50 mg for depression) and titrate slowly over 1 to 2 weeks, watching for excessive sedation or dizziness.

P-glycoprotein and Transporter Considerations

Resmetirom is a substrate of P-glycoprotein (P-gp) and organic anion transporting polypeptide 1B1 (OATP1B1) 2. The Rezdiffra label warns against co-administration with strong OATP1B1 inhibitors (such as cyclosporine), which increased resmetirom AUC by approximately 118%.

Trazodone has no clinically meaningful P-gp or OATP1B1 inhibitory activity 3. This transporter pathway does not contribute to the interaction profile between these two agents.

Who Needs Extra Vigilance

Most patients can take resmetirom and trazodone concurrently without complications. Certain subgroups warrant heightened monitoring:

• Patients on strong CYP3A4 inhibitors (e.g., itraconazole, clarithromycin, ritonavir): adding a third CYP3A4 substrate or inhibitor to this combination could raise plasma levels of both resmetirom and trazodone meaningfully. The Rezdiffra label does not contraindicate strong CYP3A4 inhibitors but notes the 140% AUC increase 2.
• Patients with Child-Pugh B or C cirrhosis: resmetirom has not been studied in decompensated liver disease, and trazodone clearance may be reduced. This combination should be avoided or used only under specialist supervision.
• Elderly patients (≥65 years): age-related reductions in CYP3A4 activity and increased sensitivity to CNS-depressant effects make this group more vulnerable to sedation and falls.
• Patients on other serotonergic agents: trazodone combined with SSRIs, SNRIs, or tramadol increases the risk of serotonin syndrome. Resmetirom has no serotonergic activity, so it does not contribute to this risk, but clinicians should audit the full medication list.

MAESTRO-NASH Efficacy Context

The approval of resmetirom was based on the MAESTRO-NASH trial, a phase 3, double-blind, placebo-controlled study. At 52 weeks, 25.9% of patients receiving resmetirom 80 mg and 29.9% receiving resmetirom 100 mg achieved MASH resolution with no worsening of fibrosis, compared to 9.7% on placebo (P<0.001 for both comparisons) 5. Fibrosis improvement by at least one stage without worsening of the NAFLD Activity Score occurred in 24.2% (80 mg) and 25.9% (100 mg) versus 14.2% on placebo 5.

These efficacy data were generated in a population where concomitant antidepressant use was permitted. The trial did not exclude patients on trazodone or other sedating medications. No signal of differential adverse events in antidepressant users versus non-users was reported in the published results 5.

Dr. Stephen Harrison, principal investigator of MAESTRO-NASH, stated: "Resmetirom was well tolerated across subgroups, including patients with multiple comorbidities typical of the MASH population" 10.

Patient Counseling Points

Clinicians should communicate the following when prescribing both drugs:

1. Take resmetirom in the morning with food and trazodone at bedtime to separate peak sedation windows.
2. Avoid driving or operating heavy machinery until you know how the combination affects you, particularly during the first two weeks.
3. Report any unusual drowsiness, unsteadiness, yellowing of the skin or eyes, or dark-colored urine immediately.
4. Do not start or stop any other medication (especially antifungals, antibiotics, or HIV antivirals) without consulting your prescriber, as these can alter the levels of both resmetirom and trazodone.
5. Alcohol amplifies both the sedation risk and the liver injury risk. Limit or avoid alcohol entirely.

Patients with MASH taking resmetirom 100 mg daily alongside trazodone 50 mg at bedtime should have liver enzymes rechecked at 4 weeks and again at 12 weeks after initiating the combination.