As per your history is concerned both are available in the market you should know mode of action of AMBIEN as follow - Zolpidem is an imidazopyridine derivative that acts by binding to the benzodiazepine (BZD) receptors of the GABA receptor complex resulting in neuronal hyperpolarisation, action potential inhibition, increased in chloride conductance and decreased in neuronal excitability. It has strong sedative action but only minimal anxiolytic, myorelaxant and anticonvulsant properties due to its selectivity for the BZ1-receptor over the BZ2-receptor. Zolpidem has a rapid onset but short duration of hypnotic action. Onset: Immediate release: 30 min. Duration: Immediate release: 6-8 hr. Absorption: Rapidly absorbed from GI tract. Food reduces both the rate and extent of GI absorption. Absolute bioavailability: Approx 70%. Time to peak plasma concentration: Immediate release: 1.6 hr; extended release: 1.5 hr. Distribution: Distributed into breast milk. Volume of distribution: 0.54 kg/L. Plasma protein binding: Approx 92%. Metabolism: Undergoes first pass metabolism, metabolised primarily by CYP3A4 isoenzyme. Excretion: Via urine (48-67%) and faeces (29-42%) as inactive metabolites. Elimination half-life: Approx 2.5 hr. And LUNESTA is as follows- Eszopiclone may interact w/ γ-aminobutyric acid (GABA) receptor complexes at binding domains located close to or allosterically coupled to benzodiazepine receptors. Absorption: Rapidly absorbed from the GI tract. Delayed w/ high-fat or heavy meal. Time to peak plasma concentration: Approx 1 hr. Distribution: Plasma protein binding: 52-59%. Metabolism: Extensively metabolised via oxidation and demethylation by CYP3A4 and CYP2E1 isoenzymes to several active and inactive metabolites. Excretion: Via urine (up to 75%; as metabolites). Half-life: Approx 6 hr. Ambien-Zolpidem Lunesta-eszopiclone So never change any compound without the advise of Doctor(Thanks)