Abstract: A method of treating insomnia comprising administering to a subject a formulation including zaleplon, wherein the formulation is adapted to release the zaleplon after a lag time of at least about one hour after administration of the formulation, and during which substantially no drug substance is released; provide a time of peak plasma concentration of about 3 hours to about 6 hours after administration; provide an elimination half-life after the time of peak plasma concentration of about 0.5 hours to about 0.3 hours; and provide an area under the curve of about 70 ng·h/mL to about 90 ng·h/mL.