Physicochemical stability of the nefopam in elastomeric device at 0.2 and 3.33 mg/mL

Nefopam is a non-opioid analgesic used for postoperative pain control. For intravenous home use, a portable elastomeric device is often preferred for administration. The nefopam in the device must be stable at 32°C because this device is positioned close to the patient.

This study aimed to evaluate the physicochemical stability of nefopam solutions at 0.2 and 3.33 mg/mL diluted in 0.9% NaCl in silicone portable elastomeric devices at 32°C in the dark.

Three portable elastomeric devices were prepared for each condition. Chemical stability was assessed by pH measurement and high-performance liquid chromatography (HPLC). The method was validated according to the International Conference on Harmonisation Q2(R1). Stability was tested after preparation and after 6 and 24 hours of storage. At each time of analysis, the pH values were measured, and three samples from each device were analysed via HPLC. The solution is chemically stable if it retains more than 90% of its initial concentration, with the appearance of any degradation products monitored, and if the pH variation is less than one unit. Physical stability was evaluated by visual and subvisual inspection using a particle counter following the European Pharmacopoeia guidelines.

Nefopam solutions at both concentrations maintained more than 93% of their initial concentration after 6 and 24 hours at 32°C, with no pH variation exceeding one unit, demonstrating chemical stability. For both concentrations, visual inspection was compliant at each analysis time, and subvisual inspection was consistent at 24 hours. Physical stability was therefore demonstrated for both concentrations after 24 hours.

The physicochemical stability of nefopam solutions at 0.2 and 3.33 mg/mL was demonstrated for 24 hours at 32°C in portable elastomeric infusion devices. This attribute allows continuous administration at home, particularly in cases of difficulty with oral administration, or minimises the side effects of discontinuous administration.