Photostability studies on (±)-tramadol in a liquid formulation

Area of Science:

• Pharmacology
• Analytical Chemistry
• Pharmaceutical Sciences

Background:

• Tramadol ((±)-TRA) is a WHO-recommended analgesic for mild to moderate cancer pain.
• Oral liquid formulations of (±)-TRA are crucial for patients with swallowing difficulties.
• The stability of (±)-TRA in aqueous solutions under clinical conditions requires investigation.

Purpose of the Study:

• To evaluate the photostability of tramadol ((±)-TRA) in aqueous solution within a clinical context.
• To assess the impact of various light conditions (UV-A, UV-B, UV-C, sunlight, diffused light) on (±)-TRA stability.

Main Methods:

• An improved high-performance liquid chromatography (HPLC) method was utilized for enantiomeric separation and quantification of (±)-TRA.
• Photodegradation studies involved exposing (±)-TRA aqueous solutions to different UV wavelengths (UV-A, UV-B, UV-C).
• Stability was assessed in standard and light-shading dispensing bottles under simulated clinical light conditions over time.

Main Results:

• (±)-TRA degraded most rapidly under UV-C irradiation; UV-A had no significant effect.
• No significant enantiomeric differences in photodegradation were observed under UV-A, UV-B, or UV-C.
• Residual (±)-TRA levels remained high (94.6-104.3%) after 14 days under various light conditions, including sunlight and room light.

Conclusions:

• Tramadol ((±)-TRA) demonstrates excellent stability in aqueous solution when exposed to both sunlight and diffused room light.
• Liquid tramadol formulations can be reliably stored at room temperature for up to two weeks, irrespective of light protection.
• These findings support the use of liquid tramadol formulations as a viable option for effective pain management.