Stability of midazolam intranasal formula for the treatment of status epileptus in dogs.

The Purpose of this study was to determine the stability of an extemporaneously prepared intranasal formulation of midazolam for the treatment of status epileptus in dogs. An aqueous solution of midazolam (50mg/mL) was prepared by dissolving 500mg of midazolam powder in sterile water for injection containing carbopol (0.4%) and benzalkonium chloride (0.01%), pH 2.8 to 3.0. Five identical formulations were prepared and placed in light-resistant glass containers and stored under refrigeration (3*C to 5*C) and at room temperature (22*C to 24*C). Samples were collected from each container at 0, 2, 4, 8, and at 1, 3, 7, 14, 30, 45, 60, and 90 days. Each sample was diluted to an expected concentration of 200mcg/mL and assayed using high-performance liquid chromatographic analysis with ultraviolet detection. The formulation was shown to be stable for 30 days under refrigeration and at room temperature. The formulation was shown to be unstable under both storage conditions at and beyond 45 days. Stability is defined as the retention of at least 90% of the initial concentration. It is suggested that extemporaneously prepared midazolam intranasal formulation can safely be stored for 30 days at room temperature or under refrigeration.