Lunesta vs Trazodone: Combining the Two (Rationale + Risk)

Is there a studied rationale for combining them?

Neither label describes the pairing, so any rationale has to be assembled from each drug's own label and trial data.

Trazodone's side of that ledger is thin. A 2005 review of the published trazodone-for-insomnia literature identified 18 studies and concluded that the evidence was very limited, that most studies were small, done in depressed patients, had design problems and often lacked objective sleep measures, and that side effects such as sedation, dizziness and psychomotor impairment produced a high rate of discontinuation, with some evidence of tolerance [7].

What each drug is labeled for

Eszopiclone is the S-isomer of zopiclone and a Schedule IV controlled substance [1]. Its only indication is insomnia: in controlled outpatient and sleep laboratory studies it decreased sleep latency and improved sleep maintenance, and the efficacy trials ran up to 6 months [1]. The label states that the mechanism of action as a hypnotic is unclear and that the effect could relate to interaction with GABA-receptor complexes at binding domains close to or allosterically coupled to benzodiazepine receptors [1]. The starting dose is 1 mg immediately before bedtime with at least 7 to 8 hours remaining before awakening, raising to a maximum of 3 mg; 2 mg is the ceiling for elderly or debilitated patients and for anyone with severe hepatic impairment or taking a potent CYP3A4 inhibitor [1]. Terminal half-life is about 6 hours, and about 9 hours in people 65 and older [1].

Trazodone is an antidepressant labeled for major depressive disorder in adults, and the label gives no insomnia indication and no insomnia dose [2]. Current labeling calls it a selective serotonin reuptake inhibitor and 5-HT2 receptor antagonist; its preclinical binding is far tighter at 5-HT2A (35.6 nM) than at the serotonin transporter (367 nM), and it also blocks alpha-1 adrenergic receptors, which the label links to postural hypotension [2]. It is not a controlled substance [2]. The label states no half-life; a single-dose study of 100 mg in 8 healthy volunteers found a terminal half-life of 7.3 hours [3].

Where the combination rationale comes from

Eszopiclone has a labeled effect on both sleep latency and sleep maintenance. The randomized trial behind that label enrolled 788 adults aged 21 to 69 and compared eszopiclone 3 mg (n=593) with placebo (n=195) for 6 months. It showed sustained improvements in sleep latency, wake time after sleep onset, total sleep time and sleep quality, with no evidence of tolerance [8].

Trazodone's sedating effect shows up in the label's controlled outpatient depression studies: drowsiness occurred in 41% of trazodone patients versus 20% on placebo [2].

What the labels say about combining them

The Lunesta label states that additive effects occur with other CNS depressants, naming benzodiazepines, opioids, tricyclic antidepressants and alcohol, including daytime use. It says downward dose adjustment of Lunesta and the concomitant CNS depressant should be considered, and that use of Lunesta with other sedative-hypnotics at bedtime or in the middle of the night is not recommended [1].

The trazodone label states that trazodone may enhance the response to alcohol, barbiturates and other CNS depressants [2].

The shared CYP3A4 pathway

Eszopiclone is extensively metabolized by CYP3A4 and CYP2E1 [1]. Trazodone is a CYP3A4 substrate, and CYP3A4 is the enzyme that forms its active metabolite mCPP [2][9]. The trazodone label describes it only as a CYP3A4 substrate, and it does not appear in the FDA's CYP substrate, inhibitor or inducer index tables [2][10].

Strong CYP3A4 inhibitors can increase exposure to both drugs. Ketoconazole increases eszopiclone exposure, and the Lunesta label caps the dose at 2 mg when a potent CYP3A4 inhibitor is taken [1]. Strong CYP3A4 inhibitors increase trazodone exposure and the risk of adverse reactions including arrhythmia, and the trazodone label says a lower trazodone dose should be considered [2]. In 10 healthy volunteers, low-dose ritonavir cut trazodone's apparent oral clearance from 155 to 75 mL/min and lengthened half-life from 6.7 to 14.9 hours, with more sedation and fatigue [11]. Inducers push the other way: rifampicin lowered racemic zopiclone exposure by 80%, and the Lunesta label expects a similar effect with eszopiclone [1]. Strong inducers decrease trazodone exposure [2].

Risks when two sedating drugs are taken together

Next-day impairment and falls

The Lunesta label says the drug can impair daytime function at 2 mg or 3 mg even when used as prescribed, that impairment can occur without symptoms, that patients using 3 mg should be cautioned against driving the day after use, and that the risk rises with other CNS depressants, higher doses, alcohol and drugs that raise eszopiclone levels [1]. The trazodone label lists potential for cognitive and motor impairment and advises caution when operating machinery [2]. The Lunesta label also notes that patients, particularly the elderly, are at higher risk of falls [1].

Complex sleep behaviors

Lunesta carries a boxed warning: sleep-walking, sleep-driving and other activities while not fully awake may occur after the first or any subsequent dose, may result in serious injuries including death, and patients usually do not remember them; the drug is contraindicated in anyone who has had such an event [1]. These behaviors may occur with Lunesta alone at recommended doses, with or without alcohol or other CNS depressants [1]. FDA added the boxed warning and contraindication to eszopiclone, zaleplon and zolpidem after a safety announcement posted 30 April 2019; the analysis behind it identified 66 serious cases reported through 27 February 2018, including 20 deaths and 46 serious injuries [12][13].

Blood pressure, heart rhythm and priapism

In the trazodone label's outpatient depression studies, hypotension occurred in 4% of trazodone patients versus 0% on placebo, and syncope in 5% versus 1% [2]. Trazodone prolongs the QT/QTc interval, and torsades de pointes and ventricular tachycardia have been reported after marketing at doses of 100 mg/day or less with the immediate-release form [2]. The label tells men to stop the drug and get emergency care for any erection lasting more than 4 hours, painful or not, and to use caution in sickle cell anemia, multiple myeloma, leukemia or penile deformity such as Peyronie's disease [2]. Trazodone also carries a boxed warning for suicidal thoughts and behaviors in pediatric and young adult patients [2].

Serotonin syndrome

Trazodone can precipitate serotonin syndrome alone, and the risk rises with other serotonergic drugs, which the label lists as triptans, tricyclic antidepressants, fentanyl, lithium, tramadol, tryptophan, buspirone and St. John's wort; MAOIs are contraindicated [2]. The Lunesta label lists no serotonin syndrome warning and says its mechanism of action is unclear [1].

Older adults

Lunesta's total dose should not exceed 2 mg in elderly or debilitated patients [1], and the 2023 AGS Beers Criteria say to avoid eszopiclone in older adults [4]. For trazodone, the label flags orthostatic hypotension and syncope and notes that hyponatremia and SIADH carry higher risk in older adults [2].

What the guidelines say

The American College of Physicians recommends cognitive behavioral therapy for insomnia as the initial treatment for all adults with chronic insomnia (strong recommendation, moderate-quality evidence), with medication added only through shared decision-making if CBT-I alone was unsuccessful (weak recommendation, low-quality evidence) [5]. The American Academy of Sleep Medicine's 2017 pharmacologic guideline gave a weak suggestion for eszopiclone for sleep-onset and sleep-maintenance insomnia [6].

Bottom line

Lunesta is labeled for insomnia and trazodone for depression, and neither label covers using them together. Both labels warn of additive effects with other CNS depressants, both drugs are CYP3A4 substrates, and each has its own next-day impairment and safety warnings [1][2].