Microemulsion based intranasal delivery system for treatment of insomnia

The aim of this investigation was to prepare and characterize microemulsions/mucoadhesive microemulsions of Diazepam (D), Lorazepam (L) and Alprazolam (A), evaluate their pharmacodynamic performances by performing comparative sleep induction studies in male albino rats to assess their role in effective management of insomnia patients. Microemulsions of Diazepam (DME), Lorazepam (LME) and Alprazolam (AME) were prepared by titration method and characterized for drug content, globule size distribution and zeta potential, nasal toxicity and sleep induction. DME, LME and AME were transparent and stable with mean globule size and zeta potential in the range of 95.6 nm to 141.7 nm and -2.205 to -0.111 mV respectively. The prepared microemulsions exhibited reversible nasal toxicity. Onset of sleep and duration of sleep were observed in the following order: Lorazepam > Alprazolam>Diazepam. Faster onset of sleep following intranasal administration of microemulsions (<20 min) compared to oral administration (29-33 min) and control group (>45 min) for all three drugs suggested selective nose-to-brain transport of drug(s). Intranasal administration of microemulsion based formulations resulted in even faster onset of sleep (<12 min) with intranasal mucoadhesive microemulsion(s) resulting in fastest onset of sleep (<9 min). Duration of sleep was longest with the intranasal mucoadhesive microemulsions. These results are suggestive of larger extent of distribution of drug(s) to brain after intranasal administration of mucoadhesive microemulsion(s). These results are further corroborated with by loss or rightening reflex and startle reflex at earlier time points (within 10 min and 15 min respectively) with mucoadhesive microemulsions. Thus, the results of this investigation indicated rapid and larger extent of drug transport to the rat brain resulting in rapid induction of sleep followed by prolonged duration of sleep in rats following intranasal administration of mucoadhesive microemulsion(s). However, the role of microemulsion based formulations developed in this investigation in clinical practice can only be established after animal studies in two different animal models followed by extensive clinical trials.