Background/Objectives: Using a combination of analgesics allows for the use of lower doses of each, therefore, lowering risk of side effects. The study aims to estimate the bioavailability (pharmacokinetics of enantiomers and metabolites, as well as linearity and sex-related effects) of fixed doses combinations of Ibuprofen/Tramadol via an intravenous (IV) vs. oral route, and it is interesting to bridge the gap of equipotent doses by different routes. Methods: This was a randomized, open-label, crossover, five-period pharmacokinetics clinical trial, in which a single dose of each formulation [four different strengths of Ibuprofen 400 mg/Tramadol HCl (30, 31.5, 33, 37.5 mg), intravenous; Ibuprofen/Tramadol HCl 400 mg/37.5 mg, granules for oral solution], were administered to healthy volunteers. Enantiomers of Ibuprofen, of Tramadol, and of its main active metabolite O-desmethyl-Tramadol (M1) were measured, and pharmacokinetic parameters (maximal concentration (Cmax) and area under the concentration curve (AUC)) were estimated. Given the exploratory nature of the study, the sample size was small to provide sufficient power for comparisons of differences across all subgroups. The study was registered at Spanish register of clinical trials (REec), EudraCT code: 2017-001303-77. Results: Twelve subjects were recruited. Different patterns of rate and amount of the studied analytes are shown for oral and the several strengths of IV drugs tested. Ibuprofen, with an absolute oral bioavailability of 91%, showed an equivalent AUC of oral and IV administration. Tramadol showed an absolute oral bioavailability of 80%. Conclusions: Intravenous administration of Tramadol produces higher bioavailability (Cmax and AUClast) of the parent drug and lower of M1, than oral route. Dose normalized Cmax and AUClast of Tramadol and M1 were into the bioequivalence interval. Upon our pharmacokinetics study results, the intravenous dose of Tramadol should not be reduced when switching from oral dosing. No significant differences attributable to sex, once corrected by weight, were found.

Background: Drug combinations with complementary mechanisms of action are able to achieve effective analgesia at lower doses, thereby reducing the risk of adverse effects (AEs). This study evaluated the analgesic efficacy and tolerability of two fixed-dose combinations (FDCs) of ibuprofen/tramadol (IBU/TRA) compared with tramadol and a placebo. Methods: This multicenter, randomized, double-blind, dose-finding, pilot clinical trial compared IBU/TRA (400/37.5 mg and 400/75 mg) with 100 mg of tramadol and a placebo in patients with moderate-to-severe pain following dental surgery. The primary endpoints were pain intensity at 6 h (PI_6h) and the pain intensity difference from baseline to 6 h (PID_6h). PID_7h, the sum of pain intensity differences from baseline to 7 h (SPID_0–7h), pain relief (PAR_7h), total pain relief (TOTPAR_7h), the use of rescue medication and AEs were also assessed. Results: Seventy-two patients were randomized and evaluated. Both FDCs showed superiority over the placebo for PI_6h and PID_6h (p < 0.05) but were not significantly different from 100 mg of tramadol. The statistical superiority of FDCs over the placebo was observed for PID_7h, SPID_0–7h, PAR_7h and TOTPAR_7h. The percentage of patients receiving rescue medication was higher in the placebo (94.1%) and tramadol (52.6%) groups than the FDC groups (35.3% and 36.8% for 400/37.5 mg and 400/75 mg, respectively). A post hoc analysis showed that the FDCs had a superior analgesic efficacy to 100 mg of tramadol in the SPID_0–4h (p < 0.005). The incidence of AEs was comparable between treatment groups. Conclusions: Both FDCs of IBU/TRA provided superior analgesic efficacy compared to the placebo. We propose using SPID_0–4h as the preferred variable for evaluating the efficacy of this type of drug combination.