According to Wikipedia the h1 receptors stop firing to effectively manage sleep. Assuming I understand how blocking and non blocking receptors work would a full agonist on the h1 receptors effectively prevent sleep instead of create it.
The histaminergic neurons of the tuberomammillary nucleus become active during the 'wake' cycle, firing at approximately 2 Hz; during slow wave sleep, this firing rate drops to approximately 0.5 Hz. Finally, during REM sleep, histaminergic neurons stop firing altogether. It has been reported that histaminergic neurons have the most wake-selective firing pattern of all known neuronal types.