Zopiclone-Associated Taste Disturbance

Evidence for Bitter/Metallic Taste with Zopiclone

Multiple clinical studies have consistently identified unpleasant taste (described as bitter or metallic) as one of the most common adverse effects of zopiclone, occurring in approximately 7-26% of patients taking the medication 1, 2, 3
In studies examining eszopiclone (the S-isomer of zopiclone), five studies found a +0.07 risk difference for unpleasant taste compared to placebo 3
The American Academy of Sleep Medicine notes that unpleasant taste is the only consistent adverse event occurring in excess of placebo with eszopiclone 1, 3
Individual studies report even higher rates of taste disturbance, with Krystal and colleagues reporting unpleasant taste in 26.1% of eszopiclone patients versus 5.6% with placebo 2
Soares and colleagues found a significant increase in unpleasant taste with eszopiclone (17.6% versus 0.5%) 3
Joffe and colleagues reported a 15.2% risk for metallic taste 3

The benefits of zopiclone in treating insomnia are generally considered to outweigh the harms, including the bitter taste side effect 3
The taste disturbance appears to be dose-related, with higher incidence at higher doses 2, 3

This taste disturbance, while bothersome to some patients, is generally not considered a serious adverse effect that would preclude the use of zopiclone in appropriate patients with insomnia 1, 3