A randomised controlled trial of a novel tramadol chewable tablet: pharmacokinetics and tolerability in children

Tramadol is a bitter atypical opioid analgesic drug and is prescribed to treat postoperative pain in children. However, in many countries there is no licensed paediatric tramadol formulation available. We have formulated a novel chewable chocolate-based drug delivery system for the administration of tramadol to children. This pilot, single-centre, open-label, randomised clinical study assessed the taste tolerability and comparative population pharmacokinetics of the novel tramadol chewable tablet against a compounded tramadol hydrochloride oral liquid, at a dose of 1 mg.kg^-1 . A 5-point facial hedonic scale was used by the children, parents and nurses to assess tolerability. One hundred and forty-one children aged 3-16 years were given tramadol 30 min before general anaesthesia. Blood samples were taken following the induction of anaesthesia and for up to 5 h following tramadol administration. Tramadol and its active metabolite O-desmethyltramadol were analysed using reversed-phase high-performance liquid chromatography. A population pharmacokinetic model was built using non-linear mixed effects modelling. The relative bioavailability for the tablet was 1.25 times higher (95%CI 1.16-1.35) than for tramadol hydrochloride oral liquid, while the absorption rate constant for the tablet was significantly lower (1.97 h^-1 vs. 3.34 h^-1 , p < 0.001). Larger inter-individual variability in absorption rates were observed with the liquid tramadol. The tramadol chewable tablet was more acceptable in taste to children when assessed by the children, parents and nurses (all p < 0.001). We conclude that the novel tramadol chewable tablet has favourable acceptability and more reliable relative bioavailability in children compared with tramadol hydrochloride oral liquid.

HPLC-UV assay of tramadol and O-desmethyltramadol in human plasma containing other drugs potentially co-administered to participants in a paediatric population pharmacokinetic study

Multimodal analgesia is employed in paediatric pain management to maximise analgesia and minimise side effects. Tramadol is dosed at 1-1.5 mg/kg to treat severe pain in children but the assay for tramadol in plasma samples for pharmacokinetic and toxicology studies does not often consider concurrently administered medications. In this study we developed and validated an HPLC-UV method to quantify tramadol and its main metabolite (O-desmethyltramadol) in human plasma in the presence of seven potentially interfering drugs. Sample preparation method was developed by combining liquid-liquid extraction and protein precipitation. Chromatographic separation was achieved on a BDS-Hypersil-C18 column (5 µm, 250 × 4.6 mm) using a double gradient method. The limit of quantification was 6.7 ng/ml for both tramadol and ODT. The precision and accuracy were in compliance with ICH guidelines. This method was successfully employed to analyse the blood samples of 137 paediatric participants in a tramadol pharmacokinetic trial.