In vitro performance evaluation of a self-emulsifying anhydrous suspension vehicle for enteral drug administration

Administration of oral medications through enteral feeding tubes presents many challenges. Although anhydrous suspension vehicles may offer advantages for poorly water-soluble or hydrolysis-sensitive drugs, their suitability for enteral administration has not been well characterized. This study evaluated the performance of a self-emulsifying anhydrous suspension vehicle. Metronidazole 50 mg/mL suspensions prepared in the self-emulsifying anhydrous suspension vehicle and two commonly used non-self-emulsifying anhydrous vehicles were compared for residual deposition and drug recovery following administration through feeding tubes. Based on preliminary findings, the self-emulsifying vehicle was further evaluated using five representative formulations - metronidazole 50 mg/mL, doxycycline 100 mg/mL, nifedipine 4 mg/mL, chloroquine 10 mg/mL, and valacyclovir 50 mg/mL - for potency, content uniformity, tube occlusion risk, drug recovery, osmolality, and compatibility with feeding tube materials using various tube types and sizes. For the metronidazole formulation, the self-emulsifying vehicle showed minimal residual deposition after repeated administration and more consistent drug recovery. All tested formulations demonstrated acceptable potency and content uniformity. Drug recovery exceeded 90% across all evaluated formulations. Tube occlusion was formulation- and tube size-dependent. Due to its anhydrous nature, the self-emulsifying vehicle itself had no measurable osmolality. After 1:5 dilution, all tested formulations exhibited osmolality below or around 300 mOsm/kg. No evidence of degradation or structural changes in feeding tube materials was observed following vehicle exposure. The self-emulsifying anhydrous suspension vehicle demonstrated favorable performance for enteral drug administration. These findings support its potential as an alternative vehicle for enteral administration of challenging oral medications.