The generic versions of Ambien and Sonata (zolpidem and zaleplon) have dominated the market for insomnia medications. Zolpidem is available as a 5 or 10 mg tablet and Zaleplon 5, 10, or 20 mg tablets. If your insurance company covers one and not the other, how easy is it to change? How do the Z drugs compare?
Both are “atypical benzos” that have a high affinity for alpha 1 GABA receptors. This sets them apart from other “typical” benzodiazepines (Ativan, Valium, Xanax) because they working to promote sleep, but not to treat anxiety.
Why are they so popular?
They both have been shown to improve sleep with no evidence of tolerance seen with long-term use. Tolerance is the loss of effect with repeated use of a standard dose, and is not seen with the Z drugs. Importantly, they have been shown to improve aspects of daytime function in those suffering from insomnia.
How are they different?
Zaleplon has a very short half-life of about one hour, shorter than zolpidem. Zolpidem has a half-life of approximately 1.5 to 2.4 hours. More specifically, zolpidem 5 and 10 mg tablets reach maximum concentration (Tmax) at 1.6 hours, with a half life 1.4 – 4.5 hours. Zaleplon 5, 10 and 20 mg tablets reach maximum concentration at an hour, with a half life of 1 hour. Zaleplon will act more rapidly and be gone from your system more rapidly.
Who should use what?
Both are effective for patients who have difficulty falling asleep (sleep onset insomnia), but may not be as effective for patients who have difficulty maintaining sleep. For difficulty maintaining sleep you would think about a longer acting option in the same class like zolpidem CR (generic Ambien CR) or eszopiclone, the Lunesta generic. The upside to the very short half-lives of the Z drugs is the reduced potential for hangover sleepiness after normal sleep periods.
Which one is stronger?
Probably because it hangs around longer, zolpidem use has been shown to affect performance on measures of attention and verbal memory and psychomotor speed, while zaleplon has not shown those effects.
What’s the upshot?
For patients with sleep onset insomnia, a short-acting medication is a reasonable choice for an initial trial of medication therapy. This should improve the insomnia with less residual sleepiness the following morning. Zolpidem and zaleplon are both good examples of short-acting medications with a duration of effect of less than 8 hours.