The present invention relates to a new drug delivery strategy based on prodrug conversion, in which a water-soluble prodrug and its converting enzyme are co-delivered and at a point of administration such as the nasal or buccal mucosa. Enzymatic conversion of the prodrug produces drug in concentrations exceeding the drugs thermodynamic solubility, or saturation level. The supersaturated drug crosses the mucosal membrane quickly, as a result of its high thermodynamic activity, prior to crystallization. This strategy is particularly useful when fast action is required, for example in preventing or responding rapidly to Status Epilepticus (SE) or other central nervous system conditions such as migraine.
