Comparative Pharmacokinetics Between Two Tablets of Tramadol 37.5 Mg/acetaminophen 325 Mg and One Tablet of Tramadol 75 Mg/acetaminophen 650 Mg for Extended-Release Fixed-Dose Combination

An extended-release (ER) fixed-dose combination (FDC) of tramadol 37.5 mg/acetaminophen 325 mg was developed due to the demand for varying dosages. This study aimed to evaluate the pharmacokinetics (PKs) for two tablets of the new developed tramadol 37.5 mg/acetaminophen 325 mg ER FDC (DW-0920, Wontran Semi ER®) as test formulation compared to one tablet of the tramadol 75 mg/acetaminophen 650 mg ER FDC (DW-0919, Wontran ER®) as reference formulation. A randomized, open-label, 2-way crossover study was conducted in 30 healthy subjects. Subjects were orally administered one of 2 formulations followed by an alternate formulation with a 7-day washout period. Blood samples were collected up to 36 hours post-dose. Plasma concentrations of tramadol and acetaminophen were determined using a validated high-performance liquid chromatography with tandem mass spectrometric method. The geometric mean ratios (GMRs) and their 90% confidence intervals (90% CIs) of test formulation to reference formulation were calculated for the maximum plasma concentration (Cmax) and the area under the plasma concentration-time curve from zero to the last measurable time point (AUClast). The PK profiles of 2 formulations were comparable. The GMRs (90% CI) of Cmax and AUClast for tramadol were 1.086 (1.047–1.127) and 1.008 (0.975–1.042), respectively. The corresponding values for acetaminophen were 0.956 (0.897–1.019) and 0.986 (0.961–1.011), respectively. All the values were within the bioequivalence range of 0.80–1.25. Two tablets of DW-0920 were comparable to one tablet of DW-0919. The DW-0920 may be used for optimal pharmacotherapy for pain control with a lower dose. Trial Registration ClinicalTrials.gov Identifier: NCT01606059