In vitro Release of New Modified-Release Tramadol HCl Designs and Their Rheological Characterization

Elizabeth Ortega, Maria J. Bernad, Jesus Gracia, Dinorah Vargas and Luis Ocampo

Background and Objectives: Tramadol is a widely used analgesic due to its efficacy and lower incidence of adverse effects, but it has a short time of action. In this study, various formulations of 5% tramadol HCl in a poloxamer 407-based matrix system were designed at different concentrations (10, 14, 17 and 20%) to achieve a modified release formulation. Materials and Methods: Rheological-characterization and release in vitro using an Ultraviolet (UV) spectrophotometer. The results were compared with tramadol salts without excipients (T) and reference medicine (R). The follow-up time was 72 hrs and the use or absence of a dialysis membrane with a porosity of 50 kDa was also compared. Results: When the membrane was used, the formulations name TP₁₀, TP₁₄, TP₁₇ and TP₂₀ had a release of 98, 50, 23 and 16% each at 72 hrs, exceeding 3 times the release time of T and R. When membranes are not used, the TP₁₇ and TP₂₀ formulations achieved this in 48 hrs instead of the 2 hrs required by the T and R formulations. The use of the 50 kD dialysis membrane was more discriminating as it allowed to differentiate both the quantity and the speed of the tramadol release process. Conclusion: Modified-release formulations were obtained, which retain and prolong tramadol hydrochloride release to the reference medicine, which could reduce the daily dose frequency and help to comply with the analgesic treatment in patients with pain.

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