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Objective To compare the analgesic efficacy and side effects of the synthetic cannabinoid nabilone with those of the weak opioid dihydrocodeine for chronic neuropathic pain. Design Randomised, double blind, crossover trial of 14 weeks’ duration comparing dihydrocodeine and nabilone.Setting Outpatient units of three hospitals in the United Kingdom.Participants 96 patients with chronic neuropathic pain, aged 23-84 years. Main outcome measures The primary outcome was difference between nabilone and dihydrocodeine in pain, as measured by the mean visual analogue score computed over the last 2 weeks of each treatment period. Secondary outcomes were changes in mood, quality of life, sleep, and psychometric function. Side effects were measured by a questionnaire.Intervention Patients received a maximum daily dose of 240 mg dihydrocodeine or 2 mg nabilone at the end of each escalating treatment period of 6 weeks. Treatment periods were separated by a 2 week washout period.Results Mean baseline visual analogue score was 69.6 mm (range 29.4-95.2) on a 0-100 mm scale. 73 patients were included in the available case analysis and 64 patients in the per protocol analysis. The mean score was 6.0 mm longer for nabilone than for dihydrocodeine (95% confidence interval 1.4 to 10.5) in the available case analysis and 5.6 mm (10.3 to 0.8) in the per protocol analysis. Side effects were more frequent with nabilone.Conclusion Dihydrocodeine provided better pain relief than the synthetic cannabinoid nabilone and had slightly fewer side effects, although no major adverse events occurred for either drug. Trial registration Current Controlled Trials ISRCTN15330757.

Background and Objectives Currently, the majority of the surgical procedures performed in paediatric hospitals are done on a day care basis, with post-operative pain being managed by caregivers at home. Pain after discharge of these post-operative children has historically been managed with oral codeine in combination with paracetamol (acetaminophen). Codeine is an opioid, which elicits its analgesic effects via metabolism to morphine and codeine-6-glucuronide. Oral morphine is a feasible alternative for outpatient analgesia; however, the pharmacokinetics of morphine after oral administration have been previously described only sparsely, and there is little information in healthy children. Methods The clinical trial included 40 children from 2 to 6 years of age, with an American Society of Anaesthesiologists physical status classification of 1 or 2, who were undergoing surgical procedures requiring opioid analgesia. Morphine was orally administered prior to surgery in one of three doses: 0.1 mg/kg, 0.2 mg/kg and 0.3 mg/kg. Blood samples were collected for plasma morphine, morphine-3-glucuronide (M3G) and morphine-6-glucuronide (M6G) concentrations at 30, 60, 90, 120, 180 and 240 min after administration. All analyses were performed with the non-linear mixed-effect modelling software NONMEM version 7.2, using the first-order conditional estimation (FOCE) method. Results A pharmacokinetic model was developed to simultaneously describe the plasma profiles of morphine and its metabolites M3G and M6G after a single dose of oral morphine in young children (2–6 years of age). The disposition of morphine, M3G and M6G in plasma was best described by a one-compartment model. M3G and M6G metabolite formation was best described by a delay transit compartment, indicating a delay in the appearance of these two major metabolites. Conclusion This model provides a foundation on which to further evaluate the use of oral morphine and its safety in young children. Longer follow-up time for morphine oral doses and incorporation of other important covariates, such as phenotype, will add value and will help overcome the limitations of the presented population pharmacokinetic analysis.

Several over-the-counter (OTC) drugs are known to be misused. Among them are opioids such as codeine, dihydrocodeine, and loperamide. This work elucidates their pharmacology, interactions, safety profiles, and how pharmacology is being manipulated to misuse these common medications, with the aim to expand on the subject outlined by the authors focusing on abuse prevention and prevalence rates. The reviewed literature was identified in several online databases through searches conducted with phrases created by combining the international non-proprietary names of the drugs with terms related to drug misuse. The results show that OTC opioids are misused as an alternative for illicit narcotics, or prescription-only opioids. The potency of codeine and loperamide is strongly dependent on the individual enzymatic activity of CYP2D6 and CYP3A4, as well as P-glycoprotein function. Codeine can also be utilized as a substrate for clandestine syntheses of more potent drugs of abuse, namely desomorphine (“Krokodil”), and morphine. The dangerous methods used to prepare these substances can result in poisoning from toxic chemicals and impurities originating from the synthesis procedure. OTC opioids are generally safe when consumed in accordance with medical guidelines. However, the intake of supratherapeutic amounts of these substances may reveal surprising traits of common medications.

Hair analysis for drugs has become extensively used for forensic investigation in recent years. To best interpret hair drug content in post-mortem conditions, the extent of external contamination by biological fluids, such as blood, must be taken into account to avoid false positive results. The present study evaluated opiates and opioids incorporation into hair from blood containing different concentrations of morphine (MOR), 6-mono-acetyl morphine (6-AM), codeine (COD), dihydrocodeine (DHC), tramadol (TRA), oxycodone (OXY), methadone (MET), 2-ethylidene-1,5-dimethyl-3,3- diphenyl pyrrolidine (EDDP), buprenorphine (BUP) and norbuprenorphine (NBUP). The hair strands contaminated by brief soaking into blood were stored at room temperature (RT) or at 4°C during 6 hours, 1, 3, 7 or 14 days. After decontamination by extensive washing, we show that all opiates and opioids were incorporated into hair within a few hours at RT and 4°C, without significant changes over time. The concentrations of opiates and opioids in hair reached the cut-off levels established by the Society of Hair Testing (SoHT) for therapeutic (MET, COD), or toxic or lethal (all other molecules) blood concentrations. The metabolite to parent drug concentration ratios were determined for NBUP/BUP, MOR/6-AM and EDDP/MET and could be helpful as indicators of blood external contamination. •Opiates and opioids incorporate deeply into hair after short exposure to blood.•No influence of temperature of storage on opiates and opioids integration into hair.•Avoid analyzing hair samples contaminated with blood containing opiates and opioids.•Metabolite to parent drug ratio could be helpful as indicator of hair contamination.

Background and Objective Codeine metabolism in humans is complex due to the involvement of multiple cytochrome P450 (CYP) enzymes, and has a strong genetic underpinning, which determines the levels of relevant CYP450 enzyme expression in vivo. Polymorphic CYP2D6 metabolises codeine to morphine via O-demethylation, while a strong correlation between CYP2D6 phenotype and opioidergic adverse effects of codeine is well documented. The aim of this study was to quantify the effect of CYP2D6 genotype on the biotransformation of codeine. Methods We conducted a prospective clinical trial with 1000 patients, during which ambulatory patients were administered 60 mg of codeine preoperatively and the association between CYP2D6 activity and morphine exposure across various CYP2D6 genotypes was quantified using a population pharmacokinetic model. Plasma concentration data for codeine and its primary metabolites were obtained from 997 patients and CYP2D6 genotype was screened for study subjects, and respective sums of activity scores assigned for each CYP2D6 allele were used as covariates in model development. Results Our final model predicts the disposition of codeine and the formation of morphine, codeine-6-glucuronide and morphine-3-glucuronide adequately while accounting for variability in morphine exposure on the basis of CYP2D6 genotype. In agreement with previous results, patients with decreased function alleles ( CYP2D6*10 and *41 ) showed varying levels of decrease in CYP2D6 activity that were inconsistent with increasing activity scores. Model simulations demonstrate that morphine concentrations in ultrarapid CYP2D6 metabolisers reach systemic concentrations that can potentially cause respiratory depression (over 9.1 ng/mL), and have 218% higher exposure (19 versus 8.7 µg · h/L, p < 0.001) to morphine than normal metabolisers. Similarly, poor and intermediate metabolisers had significantly reduced morphine exposure (1.0 and 3.7 versus 8.7 µg · h/L, p < 0.001) as compared with normal metabolisers. Conclusions Our final model leads the way in implementing model-informed precision dosing in codeine therapy and identifies the use of genetic testing as an integral component in the effort to implement rational pharmacotherapy with codeine.

Background Many opiate users entering British prisons require prescribed medication to help them achieve abstinence. This commonly takes the form of a detoxification regime. Previously, a range of detoxification agents have been prescribed without a clear evidence base to recommend a drug of choice. There are few trials and very few in the prison setting. This study compares dihydrocodeine with buprenorphine. Methods Open label, pragmatic, randomised controlled trial in a large remand prison in the North of England. Ninety adult male prisoners requesting an opiate detoxification were randomised to receive either daily sublingual buprenorphine or daily oral dihydrocodeine, given in the context of routine care. All participants gave written, informed consent. Reducing regimens were within a standard regimen of not more than 20 days and were at the discretion of the prescribing doctor. Primary outcome was abstinence from illicit opiates as indicated by a urine test at five days post detoxification. Secondary outcomes were collected during the detoxification period and then at one, three and six months post detoxification. Analysis was undertaken using relative risk tests for categorical data and unpaired t-tests for continuous data. Results 64% of those approached took part in the study. 63 men (70%) gave a urine sample at five days post detoxification. At the completion of detoxification, by intention to treat analysis, a higher proportion of people allocated to buprenorphine provided a urine sample negative for opiates (abstinent) compared with those who received dihydrocodeine (57% vs 35%, RR 1.61 CI 1.02–2.56). At the 1, 3 and 6 month follow-up points, there were no significant differences for urine samples negative for opiates between the two groups. Follow up rates were low for those participants who had subsequently been released into the community. Conclusion These findings would suggest that dihydrocodeine should not be routinely used for detoxification from opiates in the prison setting. The high relapse rate amongst those achieving abstinence would suggest the need for an increased emphasis upon opiate maintenance programmes in the prison setting. Trial registration Current Controlled Trials ISRCTN07752728

Codeine is an analgesic drug acting on μ -opiate receptors predominantly via its metabolite morphine, which is formed almost exclusively by the genetically polymorphic enzyme cytochrome P450 2D6 (CYP2D6). Whereas it is known that individuals lacking CYP2D6 activity (poor metabolizers, PM) suffer from poor analgesia from codeine, ultra-fast metabolizers (UM) due to the CYP2D6 gene duplication may experience exaggerated and even potentially dangerous opioidergic effects and no systematical study has been performed so far on this question. A single dose of 30 mg codeine was administered to 12 UM of CYP2D6 substrates carrying a CYP2D6 gene duplication, 11 extensive metabolizers (EM) and three PM. Genotyping was performed using polymerase chain reaction-restriction fragment length polymorphism methods and a single-base primer extension method for characterization of the gene-duplication alleles. Pharmacokinetics was measured over 24 h after drug intake and codeine and its metabolites in plasma and urine were analyzed by liquid chromatography with tandem mass spectrometry. Significant differences between the EM and UM groups were detected in areas under the plasma concentration versus time curves (AUCs) of morphine with a median (range) AUC of 11 (5–17)  μ g h l −1 in EMs and 16 (10–24) μ g h l −1 in UM ( P =0.02). In urine collected over 12 h, the metabolic ratios of the codeine+codeine-6-glucuronide divided by the sum of morphine+its glucuronides metabolites were 11 (6–17) in EMs and 9 (6–16) in UM ( P =0.05). Ten of the 11 CYP2D6 UMs felt sedation (91%) compared to six (50%) of the 12 EMs ( P =0.03). CYP2D6 genotypes predicting ultrarapid metabolism resulted in about 50% higher plasma concentrations of morphine and its glucuronides compared with the EM. No severe adverse effects were seen in the UMs in our study most likely because we used for safety reasons a low dose of only 30 mg. It might be good if physicians would know about the CYP2D6 duplication genotype of their patients before administering codeine.

Studying the origin of opiate and/or opiate metabolites in individual urine specimens after consumption of cold syrups is vital for patients, doctors, and law enforcement. A rapid liquid chromatography–tandem mass spectrometry method using “dilute-and-shoot” analysis without the need for extraction, hydrolysis and/or derivatization has been developed and validated. The approach provides linear ranges of 2.5–1000 ng mL−1 for 6-acetylmorphine, codeine, chlorpheniramine, and carbinoxamine, 2.5–800 ng mL−1 for morphine and morphine-3-β-d-glucuronide, and 2.5–600 ng mL−1 for morphine-6-β-d-glucuronide and codeine-6-β-d-glucuronide, with excellent correlation coefficients (R2 > 0.995) and matrix effects (< 5%). Urine samples collected from the ten participants orally administered cold syrups were analyzed. The results concluded that participants consuming codeine-containing cold syrups did not routinely pass urine tests for opiates, and their morphine–codeine concentration ratios (M/C) were not always < 1. In addition, the distribution map of the clinical total concentration of the sum of morphine and codeine against the antihistamines (chlorpheniramine or carbinoxamine) were plotted for discrimination of people who used cold syrups. The 15 real cases have been studied by using M/C rule, cutoff value, and distribution map, further revealing a potential approach to determine opiate metabolite in urine originating from cold syrups.

The study aimed to assess the effects of codeine medication on some oxidative stress parameters and how it affects the expression of enolase in neuronal cells. The codeine medication used for the study was Archilin™ with codeine syrup and dihydrocodeine 30 mg. The study used 30 male Wistar rats which were grouped in five: A, B, C, D, and E ( n  = 6), while treatments were administered for 21 days. Based on the LD 50 s of 6.09 ml/kg body weight (b.wt.) Archilin™ with codeine syrup and 3.145 mg/kg b.wt. dihydrocodeine, group A served as control and were given normal saline; groups B and C were treated with 1 mg/kg and 2 mg/kg b.wt. dihydrocodeine, respectively; while groups D and E were treated with 2 ml/kg and 4 ml/kg b.wt. Archilin™ with codeine syrup, respectively. After treatments, animals were sacrificed via cervical dislocation and the brains were harvested and prepared for determination of oxidative stress biomarkers as well as immunohistochemical studies of neuron-specific enolase (NSE) to assess for neuronal cell integrity. Significantly decreased mean values ( p  < 0.05) of superoxide dismutase (SOD) and catalase (CAT) activities were observed while malondialdehyde (MDA) is significantly increased ( p  < 0.05) among treated groups. The expression of enolase was downregulated in treatment groups when compared to control. Animals in group A which are control showed strong staining intensity of the prefrontal cortex compared to groups C, D, and E which showed mild staining. The scoring of group A for cerebellum showed strong staining intensity, groups B and C showed mild staining, while groups D and E showed weak staining intensity. From the findings of this study, prolonged codeine syrup administration causes oxidative stress and this affects the expression of enolase in neuronal cells resulting in glucose hypometabolism which eventually results in functional brain failure.

Conventional mammillary models are frequently used for pharmacokinetic (PK) analysis when only blood or plasma data are available. Such models depend on the quality of the drug disposition data and have vague biological features. An alternative minimal-physiologically-based PK (minimal-PBPK) modeling approach is proposed which inherits and lumps major physiologic attributes from whole-body PBPK models. The body and model are represented as actual blood and tissue (usually total body weight) volumes, fractions ( f d ) of cardiac output with Fick’s Law of Perfusion, tissue/blood partitioning ( K p ), and systemic or intrinsic clearance. Analyzing only blood or plasma concentrations versus time, the minimal-PBPK models parsimoniously generate physiologically-relevant PK parameters which are more easily interpreted than those from mammillary models. The minimal-PBPK models were applied to four types of therapeutic agents and conditions. The models well captured the human PK profiles of 22 selected beta-lactam antibiotics allowing comparison of fitted and calculated K p values. Adding a classical hepatic compartment with hepatic blood flow allowed joint fitting of oral and intravenous (IV) data for four hepatic elimination drugs (dihydrocodeine, verapamil, repaglinide, midazolam) providing separate estimates of hepatic intrinsic clearance, non-hepatic clearance, and pre-hepatic bioavailability. The basic model was integrated with allometric scaling principles to simultaneously describe moxifloxacin PK in five species with common K p and f d values. A basic model assigning clearance to the tissue compartment well characterized plasma concentrations of six monoclonal antibodies in human subjects, providing good concordance of predictions with expected tissue kinetics. The proposed minimal-PBPK modeling approach offers an alternative and more rational basis for assessing PK than compartmental models.