Trazodone Dosing in Renal Impairment: Evidence-Based Adjustments for Kidney Disease

Does trazodone need a lower dose in kidney disease?

The label's Dosage and Administration section sets one adult regimen for major depressive disorder: an initial 150 mg/day in divided doses, increased by 50 mg/day every 3 to 4 days [1]. The label states that the outpatient dose usually should not exceed 400 mg/day in divided doses, and that severely depressed inpatients may be given up to but not in excess of 600 mg/day [1]. That section gives no kidney-based starting dose, no eGFR threshold and no separate maximum [1].

The only other dose changes the label describes are for strong CYP3A4 inhibitors, where it says to consider a lower dose based on tolerability, and strong CYP3A4 inducers, where a higher dose may be needed [1]. The labeled indication is major depressive disorder in adults, and the label gives no insomnia dose, so bedtime use for sleep is off-label [1].

What the label flags that matters alongside kidney disease

Heart rhythm. The label states that trazodone prolongs the QT/QTc interval, and it identifies known QT prolongation, a history of arrhythmia, low potassium or magnesium, congenital long QT, and other QT-prolonging drugs as situations in which trazodone should be avoided [1]. Torsades de pointes and ventricular tachycardia have been reported postmarketing at doses of 100 mg/day or less with the immediate-release tablets [1].

Blood pressure. Orthostatic hypotension and syncope are label warnings, and the label notes that taking trazodone with blood pressure medicines may require lowering the blood pressure drug dose [1].

Other warnings. Hyponatremia and SIADH are label warnings, with higher risk in older adults, and serotonin syndrome can occur with trazodone alone [1]. The label tells men to stop the drug and get emergency care for an erection lasting more than 4 hours, painful or not [1].

Drug interactions the label addresses

Strong CYP3A4 inhibitors raise trazodone exposure and the risk of adverse reactions including arrhythmia [1]. In a crossover study of 10 healthy volunteers, 50 mg of trazodone with low-dose ritonavir (200 mg, four doses) lowered apparent oral clearance from 155 to 75 mL/min and raised half-life from 6.7 to 14.9 hours [3]. The label also advises measuring digoxin or phenytoin levels before combining them with trazodone, and monitoring INR when trazodone is started or stopped in patients taking warfarin [1].

What is not known

Trazodone is extensively metabolized, with under 1% of an oral dose excreted unchanged in urine, and 89 to 95% protein bound; only CYP3A4 formed the active metabolite mCPP in human liver microsomes and expressed enzymes [1][4][5]. The pharmacokinetic studies cited on this page were done in healthy volunteers or in vitro [2][3][4][5]. The Dosage and Administration section and these studies give no starting dose, titration pace or ceiling for someone with an eGFR under 30 or on dialysis.