Stability of Extemporaneous Oral Tramadol, Fluoxetine, and Doxycycline Suspensions in SyrSpend SF pH4

Extemporaneous compounding in veterinary practice sometimes represents the only possibility for treating animals in the absence of appropriate commercial formulations, especially for particular species. This method involves manipulating pharmaceutical active ingredients to a suitable dosage and formulation for administration to humans or animals. However, veterinarians and pharmacists should focus on the risk of potential incompatibilities and instability of their preparations. To help practitioners in drug compounding, we investigated the stability of oral suspensions of tramadol, fluoxetine, and doxycycline in a commercial ready-to-use vehicle (SyrSpend). A validated high-performance liquid chromatography method was developed to assay these active pharmaceutical ingredients. The oral suspensions were prepared at two concentration ranges and were stored in amber glass bottles under refrigerated conditions and at room temperature. After 90 days, the average recovery rates were between 90% and 110% for tramadol (5 mg/mL to 30 mg/mL) and doxycycline  (2 mg/mL to 10 mg/mL) without organoleptic modification. For fluoxetine, only the formulation at 2 mg/mL was stable; at higher concentrations, the uniformity of the suspension was compromised.