Lunesta and Finasteride Interaction: What Patients and Clinicians Need to Know

Does eszopiclone interact with finasteride?

No interaction between the two is described on either label. The Lunesta drug interactions section covers alcohol and other CNS depressants, olanzapine, strong CYP3A4 inhibitors such as ketoconazole, and the CYP3A4 inducer rifampicin; finasteride is not among them [1]. The Propecia (finasteride 1 mg) label states that no drug interactions of clinical importance have been identified and that finasteride does not appear to affect the cytochrome P450-linked drug-metabolizing enzyme system [2].

The two drugs do share a metabolic pathway. Finasteride is metabolized mainly by CYP3A4, and CYP3A4 is a major elimination pathway for eszopiclone [1][2]. The finasteride label does not discuss CYP3A4 inhibitors or inducers; the interaction work it reports used antipyrine, digoxin, propranolol, theophylline and warfarin, with no clinically meaningful interactions found [2].

Who is prescribed each drug

Finasteride 1 mg is indicated for male pattern hair loss in men only, and the 5 mg tablet for symptomatic benign prostatic hyperplasia [4][5]. Eszopiclone is indicated for the treatment of insomnia [1].

How each drug is cleared

Eszopiclone is extensively metabolized by oxidation and demethylation through CYP3A4 and CYP2E1, and less than 10% of a dose is excreted unchanged in urine [1]. Ketoconazole, a potent CYP3A4 inhibitor, increased eszopiclone exposure, and the label expects itraconazole, clarithromycin, nefazodone and ritonavir to behave the same way. The Lunesta label limits the total eszopiclone dose to 2 mg when a potent CYP3A4 inhibitor is co-administered [1]. In the other direction, rifampicin lowered racemic zopiclone exposure by 80%, and a similar effect is expected with eszopiclone [1].

Finasteride 1 mg peaks 1 to 2 hours after a dose, is about 90% protein bound, and has a mean terminal half-life of about 5 to 6 hours in men aged 18 to 60 and about 8 hours in men over 70 [2]. Its effect on DHT outlasts the plasma half-life because the Type II 5-alpha-reductase enzyme complex turns over slowly, roughly 30 days [2].

The sedation risk sits with eszopiclone

Eszopiclone is a CNS depressant and can impair daytime function at 2 mg or 3 mg even when used as prescribed; impairment can occur without symptoms and may not be picked up on an ordinary clinical exam [1]. The label lists what raises next-day impairment risk: taking it with less than 7 to 8 hours of sleep remaining, a higher dose, other CNS depressants, and other drugs that raise eszopiclone blood levels [1]. Patients using 3 mg should be cautioned against driving the day after use, and the elderly are at higher risk of falls [1].

The Lunesta label carries a boxed warning titled COMPLEX SLEEP BEHAVIORS: sleep-walking, sleep-driving and other activities while not fully awake may occur, some with serious injuries including death, and the label says Lunesta should be discontinued immediately if one occurs [1]. Eszopiclone is contraindicated in anyone who has had a complex sleep behavior after taking it [1]. FDA added that boxed warning and contraindication to eszopiclone, zaleplon and zolpidem after a safety announcement posted 30 April 2019; its analysis of 66 serious cases across the three drugs, reported through 27 February 2018, found 20 deaths and 46 serious injuries [6][7].

Two smaller points from the label: eszopiclone should be taken immediately before bedtime, since taking it while still up and about may cause short-term memory impairment, hallucinations, impaired coordination, dizziness and lightheadedness, and use with another sedative-hypnotic at bedtime or in the middle of the night is not recommended [1]. Alcohol adds psychomotor impairment, and olanzapine lowered DSST scores through a pharmacodynamic interaction with no change in either drug's pharmacokinetics [1].

Older adults taking both

Eszopiclone exposure is about 41% higher in people 65 and older, with a terminal half-life of about 9 hours, and the total dose should not exceed 2 mg in elderly or debilitated patients [1]. The 2023 AGS Beers Criteria list eszopiclone among medications best avoided in adults 65 and older [3]. The American College of Physicians recommends cognitive behavioral therapy for insomnia as initial treatment (strong recommendation, moderate-quality evidence), with medication considered through shared decision-making only when CBT-I alone has been unsuccessful (weak recommendation, low-quality evidence) [8]. The American Academy of Sleep Medicine gave a weak suggestion for eszopiclone in sleep-onset and sleep-maintenance insomnia [9].

Mood effects: two separate label signals

The Lunesta label warns that worsening of depression or suicidal thinking may occur and says to prescribe the least number of tablets feasible [1]. Finasteride's postmarketing section lists depression, suicidal ideation and behavior; the label notes these reports are voluntary, come from a population of uncertain size, and cannot reliably establish cause [2]. FDA ordered a safety labeling change in 2022 that cited suicidal ideation and behavior [10].

Doses and practical points

Eszopiclone is started at 1 mg immediately before bedtime with at least 7 to 8 hours remaining before awakening, may be raised to 2 mg or 3 mg if clinically indicated, and should not exceed 3 mg once daily; the cap is 2 mg for elderly or debilitated patients, for severe hepatic impairment, and with a potent CYP3A4 inhibitor [1]. The Lunesta label says not to take eszopiclone with or immediately after a heavy, high-fat meal; after a high-fat meal, a 3 mg dose had unchanged AUC, peak level down 21% and peak time delayed about 1 hour [1]. The label also classifies eszopiclone as a Schedule IV controlled substance [1].

Propecia is one 1 mg tablet once daily with or without food, with three months or more of daily use usually needed before benefit appears and continued use needed to sustain it [2]. Proscar, the 5 mg tablet for an enlarged prostate, is taken once daily [11].