Simultaneous determination of tramadol and paracetamol in human plasma using LC-MS/MS and application in bioequivalence study of -fixed-dose combination.

The study aimed to develop a sensitive and high-throughput liquid chromatography coupled with tandem mass spectrometry method to quantify concentrations of tramadol and paracetamol simultaneously in human plasma. Sample preparation involved single-step protein precipitation using methanol and two deuterated internal standards, tramadol D6 and paracetamol D4. Agilent Poroshell 120 EC-C18 (100 × 2.1 mm, 2.1 µm) analytical column was employed to achieve chromatographic separation. Detection was in positive ion multiple reaction monitoring mode. A tailing factor (Tf) of <1.2, separation factor (K prime) of >1.5 from the column dead time and signal-to-noise (S/N) ratio >10, were obtained for analytes and internal standards. The standard curve was linear over the concentration range of 2.5-500.00 ng/mL for tramadol and 0.025-20.00 µg/mL for paracetamol. A small injection volume of 1 µL, low flow rate of 440 µL/min and short analysis time of 3.5 min reduced the solvent consumption, analysis cost and system contamination. The results of method validation parameters fulfilled the acceptance criteria of bioanalytical guidelines. The method was successfully applied to a bioequivalence study of fixed-dose combination products of tramadol and paracetamol in Malaysian healthy subjects.

Persistence of N-oxides transformation products of tertiary amine drugs at lab and field studies.

This work aimed at studying the formation and persistence of N-oxides transformation products (TPs) of tertiary amine drugs by combining laboratory and field studies relevant for surface water. A monitoring study using passive samplers was first achieved for assessing attenuation of selected pharmaceuticals and their related N-oxides and N-, O-dealkylated TPs (i.e., venlafaxine, tramadol, amisulpride and sulpiride) along a 1.7 km river stretch between two sampling sites. This study revealed the stability of tramadol-N-oxide, amisulpride-N-oxide and the fast dissipation of O-desmethylvenlafaxine-N-oxide, as well as the significance of N-oxidized TPs in comparison to N-dealkylated TPs and parent compounds in river. Lab-scale experiments were then implemented for a better understanding of their mechanisms of formation and degradation under aerobic water/sediment testing and under simulated solar photochemistry. N-oxidation reactions were always a minor transformation pathway under both degradation conditions with respect to N-and O-dealkylation reactions. The amount of generated N-oxides were similar for venlafaxine, tramadol and sulpiride and peaked in the 8.4-12.8% and <4% of their initial concentration (100 µg/L), during photodegradation and biodegradation experiments, respectively. Other transformation pathways such as hydroxylation and α-C-hydroxylation followed by oxidation to amide or dehydration were also identified. Investigated N-oxides TPs (except O-desmethylvenlafaxine-N-oxide) were found stable under solar photolysis and aerobic biodegradation with a very slight reverse reaction to parent compound observed for tramadol-N-oxide and amisulpride-N-oxide. Lab-scale degradation experiments were not able to anticipate the high occurrence levels of N-oxide compounds in the environment. This was most likely due to faster degradation kinetics and/or higher sorption to sediment of parent compounds and dealkylated TPs over N-oxide TPs, resulting in higher relative accumulation of the latter.

In vitro release of new designs of modified-release tramadol hydrochloride included in a polymer matrix.

Tramadol reaches therapeutic plasma concentrations in a time interval of 0.5 to 1.7 hours, so it is necessary to dose 4 times/day, which reduces compliance with the dose and the effectiveness of the treatment. Design formulations of tramadol that allow the release time to be prolonged, surpassing those obtained with the commercial product and tramadol without excipients. Several formulations of 5% tramadol hydrochloride were designed in a matrix system based on poloxamer 407 at different concentrations (10%, 14%, 17%, and 20%). In vitro release studies were performed, using a spectrophotometer at a wavelength of 273.15 nm; were compared the results with tramadol without polymeric supplements and with the commercial formulation samples were taken in a period of time from 0.25 to 72 hours, and also compared the use or absence of dialysis membrane with a porosity of 50 kilodaltons was. With the use of the membrane, the designed formulations had a release of 98%, 50%, 23%, 16% at 72 hours, respectively, different from the commercial product and the tramadol formulation without excipients released the 24 hours. Without using dialysis membranes, a 90-100% release was achieved in the 10% and 14% formulation at 36 hours. The 17% and 20% formulation at 48 hours and the commercial formulation and tramadol without excipient were released within 2 hours. Modified release formulations were obtained, which retain and prolong the release of tramadol compared to the commercial product. Therefore, we propose to conduct further in vivo model experiments to confirm our conclusion.

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.

In Vitro and In Vivo Pharmaco-Toxicological Characterization of 1-Cyclohexyl-x-methoxybenzene Derivatives in Mice: Comparison with Tramadol and PCP.

1-cyclohexyl-x-methoxybenzene is a novel psychoactive substance (NPS), first discovered in Europe in 2012 as unknown racemic mixture of its three stereoisomers: ortho, meta and para. Each of these has structural similarities with the analgesic tramadol and the dissociative anesthetic phencyclidine. In light of these structural analogies, and based on the fact that both tramadol and phencyclidine are substances that cause toxic effects in humans, the aim of this study was to investigate the in vitro and in vivo pharmacodynamic profile of these molecules, and to compare them with those caused by tramadol and phencyclidine. In vitro studies demonstrated that tramadol, ortho, meta and para were inactive at mu, kappa and delta opioid receptors. Systemic administration of the three stereoisomers impairs sensorimotor responses, modulates spontaneous motor activity, induces modest analgesia, and alters thermoregulation and cardiorespiratory responses in the mouse in some cases, with a similar profile to that of tramadol and phencyclidine. Naloxone partially prevents only the visual sensorimotor impairments caused by three stereoisomers, without preventing other effects. The present data show that 1-cyclohexyl-x-methoxybenzene derivatives cause pharmaco-toxicological effects by activating both opioid and non-opioid mechanisms and suggest that their use could potentially lead to abuse and bodily harm.

Synthesis of a PVA drug delivery system for controlled release of a Tramadol-Dexketoprofen combination.

The local administration of analgesic combinations by means of degradable polymeric drug delivery systems is an alternative for the management of postoperative pain. We formulated a Tramadol-Dexketoprofen combination (TDC) loaded in poly(vinyl alcohol) (PVA) film. Films were prepared by the solvent casting method using three different molecular weights of PVA and crosslinking those films with citric acid, with the objective of controlling the drug release rate, which was evaluated by UV-vis spectrometry. Non-crosslinked PVA films were also evaluated in the experiments. Differential scanning calorimetry (DSC) analysis of samples corroborated the crosslinking of PVA by the citric acid. Blank and loaded PVA films were tested in vitro for its impact on blood coagulation prothrombin time (PT) and partial thromboplastin time (PTT). The swelling capacity was also evaluated. Crosslinked PVA films of higher-molecular weight showed a prolonged release rate compared with that of the lower-molecular-weight films tested. Non-crosslinked PVA films released 11-14% of TDC. Crosslinked PVA films released 80% of the TDC loaded (p < 0.05). This suggests that crosslinking films can modify the drug release rate. The blank and loaded PVA films induced PT and PTT in the normal range. The results showed that the polymeric films evaluated here have the appropriate properties to allow films to be placed directly on surgical wounds and have the capacity for controlled drug release to promote local analgesia for the control of postoperative pain.

Sigma-1 receptor antagonists: promising players in fighting neuropathic pain.

Sigma-1 receptors (S1Rs) are strongly correlated to neuropathic pain (NP), since their inactivation may decrease allodynia or dysesthesia, promoting analgesic effects. In the recent patent landscape, S1R antagonists endowed with nanomolar S1Rs affinity emerged as potent antinociceptive agents. So far, three patented compounds have been proposed for counteracting NP. Particularly PV-752 and AV1066, disclosed by the University of Pavia (Italy) and Anavex, respectively, showed good analgesic activity in preclinical studies. Moreover, E-52862 developed by Esteve (Spain) has been proved to be effective, both in preclinical and Phase II clinical trials, against several symptoms of NP. These patents ascertain S1R antagonists as potential drugs, alone or in combination with other analgesic drugs, for managing NP in humans.

Long-term stability of an infusion containing paracetamol, alizapride, ketorolac and tramadol in glass bottles at 5±3°C.

Background and objective: Infusion containing paracetamol, alizapride, ketorolac and tramadol is used after a general anaesthesia in order to limit pain, fever and nausea. Currently, these infusions are prepared according to demand in the anaesthesia unit, but the preparation in advance could improve quality of preparation and time management. The aim of this study was to investigate the long-term stability of this infusion in glass bottles at 5°C ± 3 °C. Method: Five bottles of infusion were stored at 5°C ± 3 °C for 60 days. A visual and microscope inspection were performed periodically to observe any particle appearance or colour change. pH and absorbance at three wavelengths were measured. The concentrations were measured by ultra-high performance liquid chromatography - diode array detection. Results: Multiple verifications were performed during the first 35 days and no crystal, impurity or colour change were observed. At the next time point (42nd day), crystals were visible to the naked eye. pH and absorbance at 350 nm and 550 nm were stable. A slight increase in the absorbance at 410 nm was observed during the study, suggesting that a degradation product could be formed and absorb at this wavelength. The infusion was considered chemically stable while the lower one-sided prediction limit at 95% remains superior to 90% of the initial concentration. Concentration measurements demonstrated that ketorolac and alizapride remained stable in the infusion for 35 days. The stability of tramadol was 28 days. However, degradation of paracetamol was much faster given that concentration has fallen below 90% of the initial concentration after 7 days. Conclusion: Infusion of paracetamol, alizapride, ketorolac and tramadol remains stable for 7 days in glass bottles at 5°C ± 3 °C and could be prepared in advance with these storage conditions.

Electro-Fenton treatment of the analgesic tramadol: Kinetics, mechanism and energetic evaluation.

The removal of the analgesic tramadol (TMD) from water was studied by electro-Fenton (EF) process using BDD anode. Hydroxyl radicals (OH) generated in this process are very strong oxidants and able to successfully oxidize TMD until its total mineralization in aqueous solution. The oxidative degradation of TMD was very rapid with complete disappearance of 0.1 mM (26.3 mg L-1) TMD in 10 min at 500 mA constant current electrolysis. The absolute (second order) rate constant for oxidation of TMD by OH was determined using competition kinetic method and found to be (5.59 ± 0.03) ✕ 109 M-1 s-1. The quasi-complete mineralization of the 0.1 mM TMD solution was obtained in 6 h electrolysis at 500 mA current. Several oxidation reaction intermediates were identified using GC-MS analysis. Oxalic, glyoxylic and fumaric acids were identified and their evolution during electrolysis was followed along treatment. Ammonium and nitrate ions, released during the treatment, were also considered. Based on these data and TOC removal results, a possible mineralization pathway was proposed.

Assessing the human risk and the environmental fate of pharmaceutical Tramadol.

Tramadol (TRA) is a widely used human pharmaceutical and a well-established emerging pollutant and its potential genotoxic and cytotoxic effects on humans as well as its fate in aqueous systems demand full investigation. The present study is a multidisciplinary approach and provides important insights on the potential risks of Tramadol on humans accompanied by its photolytic transformation under simulated solar irradiation. The present study revealed that Tramadol can induce genotoxic and cytotoxic effects under the specific experimental conditions, significantly depended on the tested concentration. In addition, the photolytic transformation of Tramadol was investigated in detail under simulated solar irradiation in two different water matrices: ultrapure water (UW) and treated wastewater (WW). Differences in the degradation rates were observed between UW and WW, being slower in WW. The results showed that more than 70% of Tramadol was removed after 240 min in UW ([TRA] = 10 mg L-1, I = 500 W m-2). After this period, TOC removal was found to be about 40%. Transformation of N atoms into NO3- and NH4+ followed a similar trend reaching up to 38% release. Τramadol degraded mainly by HO radicals and 1O2 through a self-sensitizing process while direct photolysis was also significant. Hydroxylation, demethylation and N-oxidation of the parent compound were found to be the main degradation pathways confirming the important role of HO and 1O2 in the photolytic process. Toxicity measurements showed a noticeable increase of the inhibition for Vibrio fischeri at the first stages which coincide with the formation of the major TPs.

A novel open-tubular capillary electrochromatography using carboxymethyl-ß-cyclodextrin functionalized gold nanoparticles as chiral stationary phase.

Enantioselective open tubular capillary electrochromatography with carboxymethyl-ß-cyclodextrin conjugated gold nanoparticles as stationary phase was developed. This novel open tubular column was fabricated through layer-by-layer self-assembly of gold nanoparticles on a 3-mercaptopropyl-trimethoxysilane-modified fused-silica capillary and subsequent surface functionalization of the gold nanoparticles through self-assembly of 6-mercapto-ß-cyclodextrin. The 6-mercapto-ß-cyclodextrin was firstly synthesized and determined by extensive spectroscopic data. Scanning electron microscopy, energy dispersive X-ray analysis spectroscopy, and electroosmotic flow experiments were carried out to characterize the prepared open tubular column. Then, the separation effectiveness of the open tubular column was verified by two pairs of ɑ-tetralones derivatives enantiomers and two pairs of basic drug enantiomers (tramadol hydrochloride and zopiclone) as mode analytes. Factors that influence the enantioseparation were optimized, and under the optimized conditions, satisfactory separation results were obtained for the four enantiomers: compound A, compound B, tramadol hydrochloride, and zopiclone with resolutions of 3.79, 1.56, 1.03, 1.60, respectively. For the combination of gold nanoparticles and negatively charged carboxymethyl-ß-cyclodextrin, the open tubular column exhibited wider separation range for neutral and basic drugs. Moreover, the repeatability and stability of the column were studied through the run-to-run and day-to-day investigations.

A Reversed-Phase Mode LC-MS/MS Method Using a Polysaccharide Chiral Selector for Simultaneous Quantitation of Each Enantiomer of Tramadol and its Metabolites in Human Plasma and Evaluation of CYP-Mediated Stereoselective Demethylation.

BACKGROUND: The enantiomeric pharmacokinetics and metabolism of tramadol and its metabolites have not fully been understood. This study aimed to develop a reversed-phase mode liquid chromatography coupled to a tandem mass spectrometry method for the enantiomeric quantitation of tramadol and its metabolites in human plasma and to evaluate the stereoselective demethylation. METHODS: Racemic tramadol and its metabolites in plasma specimens were separated using a chiral selector coated with cellulose tris(3,5-dimethylphenylcarbamate) on silica gel under a reversed-phase mode. The mass spectrometer ran in the positive ion multiple-reaction monitoring mode. This method was performed to quantify plasma samples from 20 cancer patients treated with oral tramadol. The stereoselective demethylation was evaluated using recombinant cytochrome P450 (CYP) enzymes. RESULTS: The calibration curves of (+)- and (-)-tramadol, (+)- and (-)-O-desmethyltramadol (ODT), and (+)- and (-)-N-desmethyltramadol (NDT) were linear over the plasma concentration ranges of 6.25-800, 1.25-160, and 3.13-400 ng/mL for the respective enantiomers. In the present method, the intra- and inter-day accuracies and imprecisions were 94.2%-108.3% and 0.5%-6.0% for all analytes. The plasma concentrations of (+)-tramadol and NDT were higher than those of (-)-enantiomers. In contrast, no differences were observed between the plasma concentrations of (+)- and (-)-ODT. In the demethylation assay, the O-demethylations of tramadol and NDT by CYP2D6 were (-)-form-selective. CONCLUSIONS: The present method can be useful in the enantiomeric evaluation of tramadol and its metabolites in human plasma. Although CYP2D6 contributed to the stereoselective demethylation of tramadol, remarkable differences between (+)- and (-)-ODT were not observed in the plasma of the cancer patients.

Co-crystal of tramadol-celecoxib: preclinical and clinical evaluation of a novel analgesic.

INTRODUCTION: Pain management is a major unmet need due to the suboptimal efficacy and undesirable side effects of current analgesics. Multimodal therapies recruiting complementary mechanisms of action may help address this. Co-crystals incorporating two active pharmaceutical ingredients (APIs) constitute an innovative approach to multimodal therapy, particularly if modification of the physicochemical properties of constituent APIs can be translated into clinical benefits. AREAS COVERED: The preclinical and clinical profiles of Co-Crystal of Tramadol-Celecoxib (CTC), a novel API-API co-crystal (1:1 molecular ratio of rac-tramadol.hydrochloride and celecoxib) are described. EXPERT OPINION: CTC may provide a relevant addition to pain therapy due to its: i) unique co-crystal structure conferring differentiated intrinsic dissolution profiles on constituent APIs, ii) modified clinical pharmacokinetics (slower absorption of tramadol and faster absorption of celecoxib) compared with commercially available single-entity reference products (in agreement with modified dissolution rates), iii) superior benefit-risk ratio compared with reference products (suggested by preclinical synergistic antinociceptive effects, without potentiation of adverse effects), and iv) efficacy in a phase 2 trial of moderate to severe pain following extraction of ≥2 impacted third molars requiring bone removal, where CTC doses containing low doses of APIs exerted a significant effect. Phase 3 studies are currently ongoing.

Disinfection by-Products and Ecotoxic Risk Associated with Hypochlorite Treatment of Tramadol.

In recent years, many studies have highlighted the consistent finding of tramadol (TRA) in the effluents from wastewater treatment plants (WTPs) and also in some rivers and lakes in both Europe and North America, suggesting that TRA is removed by no more than 36% by specific disinfection treatments. The extensive use of this drug has led to environmental pollution of both water and soil, up to its detection in growing plants. In order to expand the knowledge about TRA toxicity as well as the nature of its disinfection by-products (DBPs), a simulation of the waste treatment chlorination step has been reported herein. In particular, we found seven new by-products, that together with TRA, have been assayed on different living organisms (Aliivibrio fischeri, Raphidocelis subcapitata and Daphnia magna), to test their acute and chronic toxicity. The results reported that TRA may be classified as a harmful compound to some aquatic organisms whereas its chlorinated product mixture showed no effects on any of the organisms tested. All data suggest however that TRA chlorination treatment produces a variety of DBPs which can be more harmful than TRA and a risk for the aquatic environment and human health.

Development of a novel LC-MS/MS method for detection and quantification of tramadol hydrochloride in presence of some mislabeled drugs: Application to counterfeit study.

Counterfeiting of pharmaceuticals has become a serious problem all over the world, particularly in developing countries. In the present work, a highly sensitive LC-MS/MS method was developed for simultaneous determination of tramadol hydrochloride in the presence of some suspected mislabeled drugs such as alprazolam, diazepam, chlorpheniramine maleate, diphenylhydramine and paracetamol. The prepared samples were analyzed on an API 4000 mass spectrometer using an Eclipse C18 column (3.5 µm, 4.6 × 100 mm). The mobile phase consisting of 0.01% formic acid, acetonitrile and methanol (60:20:20 v/v/v) was pumped with an isocratic elution at a flow rate of 0.7 mL min-1 . The detection was achieved on a triple quadruple tandem mass spectrometer in multiple reaction monitoring mode. The proposed method was successfully validated according to International Conference on Harmonization guidelines with respect to accuracy, precision, linearity, limit of detection and limit of quantitation. The calibration linear range for tramadol hydrochloride, alprazolam, diazepam, chlorpheniramine maleate, diphenylhydramine and paracetamol was 5-500 ng mL-1 . The results revealed that the applied method is promising for the differentiation of genuine tramadol tablets from counterfeit ones without prior separation.

Fragmentation studies of selected drugs utilized in palliative care.

The results of research on selected drugs used in palliative care are presented, including fentanyl, tramadol, metoclopramide, hyoscine butylbromide, midazolam, haloperidol, levomepromazine and clonazepam. Interpretation of their ESI mass spectra obtained by the use of a triple quadrupole linear ion trap mass spectrometer is given. As a result, fragmentation pathways described in the literature are complemented and presented with more details. On their basis, transitions for quantitative analysis are selected and chromatographic conditions for the determination of the palliative care drugs are proposed as well. These results enable future studies on palliative care drugs in elderly patients including both their quantitation in body fluids and easier identification of their metabolites.

Simultaneous chiral separation of tramadol and methadone in tablets, human urine, and plasma by capillary electrophoresis using maltodextrin as the chiral selector.

The stereoselective analysis and separation of racemic drugs play an important role in pharmaceutical industry to eliminate the unwanted isomer and find the right therapeutic control for the patient. Present study suggests a maltodextrin-modified capillary electrophoresis method for a single-run chiral separation of two closely similar opiate pain relief drugs: tramadol (TRA) and methadone (MET). The best separation method possible for the both enantiomers was achieved on an uncoated fused-silica capillary at 25°C using 100 mM phosphate buffer (pH 8.0) containing 20% (w v-1 ) maltodextrin with dextrose equivalent of 4-7 and an applied voltage of 16 kV. Under optimal conditions, the baseline resolution of TRA and MET enantiomers was obtained in less than 12 minutes. The relative standard deviations (n = 3) of 20 µg mL-1 TRA and MET were 2.28% and 3.77%, respectively. The detection limits were found to be 2 µg mL-1 for TRA and 1.5 µg mL-1 for MET. This method was successfully applied to the measurement of drugs concentration in their tablets, urine, and plasma samples.

Controlled-release in-situ gel forming formulation of tramadol containing chitosan-based pro-nanogels.

Chronic pain is one of the most prevalent health problems worldwide. Tramadol is a synthetic semi-opioid analgesic, interacting with serotonergic, adrenergic and opioid receptors to reduce the pain but its short half-life in vivo may reduce patient compliance in case of chronic pains. To overcome this problem, novel drug delivery systems have been investigated. This study focuses on a chitosan based thermoresponsive in-situ gel forming formulation intended to subcutaneous injection. To evaluate further drug release, a reversed phase high performance liquid chromatography method was developed. Then two formulations (with and without TPP) were optimized by D-optimal plan using Design-Expert statistical software and were characterized in terms of morphology, release phenomenon, texture, swelling and stability as well as in vivo response. AFM images show approximately spherical nanocavities in the homogenous TPP containing gel structure, which explain the different patterns of drug release between the two formulations. This implies that changing TPP concentration can control formation of these cavities and hence drug release rate and kinetics. Not present in the sol state, nanostructures lead to emerge of a new concept: pro-nanogels. Finally, the formulations with proper texture qualities, stability and rapid sol-gel transition in vivo could be a candidate for controlled release of therapeutic agents following subcutaneous injection.

Internet pseudoscience: Testing opioid containing formulations with tampering potential.

Drug tampering practices, with the aim to increase availability of drug delivery and/or enhance drug effects, are accessible on Internet and are practiced by some portion of recreational drug users. Not rarely, recreational misuse may result in toxic and even fatal results. The aim of the present study was to assess the tampering risk of medicaments containing different formulations of an opioid in combination with paracetamol or dexketoprofen, following the procedures reported in dedicated forums on the web. Tablets and suppositories containing codeine, tramadol and oxycodone were extracted following the reported "Cold water extraction"; dextromethorphan was extracted from cough syrup following the procedure reported as "Acid/base extraction" and fentanyl was extracted from transdermal patches according the procedure reported in Internet. The tampered products and opportunely prepared calibrators in water were analysed by liquid chromatography coupled to tandem mass spectrometry (LC-MS/MS). The separation of the analytes was carried on Agilent ZORBAX Eclipse Plus C18 (RRHT 2.1 mm × 50 mm, 1.8 µm) by the gradient elution of 0.01% formic acid in water and 0.01% formic acid in methanol. Acquisition was by MRM mode considering at least two transitions for compound. Declared recoveries for these home-made extractions claimed to exceed 99% for the opioid and to complete remove paracetamol, often associated to liver toxicity and thus to obtain a "safer" preparation. In this study, the authors demonstrated that rarely the recoveries for the opioid reached 90% and that up to 60% of the paracetamol amount remained in solution. Thus, high risks for health remained both for the potential lethality of the opioid content, but also for the sub-lethal chronic use of these mixtures, which contained still uncontrolled, ignored, but often important amounts of paracetamol.