ABSTRACT
Liquid formulations offer many advantages, from ease in dosing to ease in administration, and myriad possibilities of innovative drug delivery systems. One of the most desirable features of liquid formulations, particularly the solution forms, is the relatively lower importance of bioavailability considerations, as the drug molecules are already in the dispersed phase, removing many rate-limiting steps in the absorption of drugs. Preservatives are almost always a part of liquid formulations unless there is sufficient preservative efficacy in the formulation itself, such as due to high sugar content, the presence of antimicrobial drugs, or solvents that inhibit growth, such as alcohol. Drugs are more unstable in solution or liquid dispersion than they are in solid state, because the molecular interactions are more plausible in liquid surroundings. Nasal spray drug products contain therapeutically active ingredients that are dissolved or suspended in solutions or mixtures of excipients in nonpressurized dispensers that deliver a spray containing a metered dose of the active ingredient.
