Tramadol/Diclofenac Fixed-Dose Combination for Acute Pain Management: Bioavailability Assessment of a Generic Product

The multimodal analgesia strategy for acute pain involves using 2 or more analgesic medications with distinct mechanisms of action. This study assessed the bioavailability and tolerability of 2 tramadol hydrochloride (50 mg)/diclofenac sodium (50 mg) fixed-dose combination formulations under fed conditions to attend the Brazilian regulatory requirements for generic product registration. An open-label, randomized, single-dose, 2-period, 2-way crossover trial was conducted, including healthy subjects of both sexes. Subjects received a single dose of either the test or reference formulation of tramadol/diclofenac fixed-dose combination tablets with a 7-day washout period. Blood samples were collected up to 36 hours after dosing for tramadol and 12 hours for diclofenac and quantified using a validated liquid chromatography-tandem mass spectrometry method. Of 56 subjects enrolled, 53 completed the study. The 90% confidence intervals for maximum plasma concentration and area under the concentration-time curve from time 0 to the last quantifiable concentration were within acceptable bioequivalence limits of 80%-125%. Considering the results presented in this study, the test formulation is bioequivalent to the reference formulation and could be interchangeable in medical practice.