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Background: A considerable inter‐individual variability has been reported in the relationship between methadone doses applied and serum concentrations achieved in methadone maintenance treatment. However, the underlying causes for this variability are not fully understood. Objectives: We investigated the influence of genetic, pathophysiological and pharmacological factors on serum methadone concentration‐to‐dose ratio (CDR) and discussed the clinical implications of the findings. Methods: We used data from two retrospective laboratory databases and a prospective cohort study to investigate the impact on methadone CDR of hepatic cytochrome P450 enzyme system (CYP) genetic polymorphisms, age, sex, concomitant medication, liver fibrosis and body mass index through linear mixed model analyses. Findings: A positive association was found between CDR and the homozygous CYP2B6*6 genotype, concurrent treatment with CYP3A4 inhibitors and body mass index. CDR was lower among women and during concomitant use of CYP inducers. CDR was not associated with age or the degree of liver fibrosis in our investigations. Conclusions: This research work supports the need for individually tailored dosage considering the various factors that influence methadone CDR. The gained knowledge can contribute to reducing the risks associated with the treatment and optimizing the desired outcomes. [ABSTRACT FROM AUTHOR]

Some ecological studies have shown that areas with higher use of cannabis may have lower opioid use and fewer opioid‐related problems. Newer studies are questioning this finding. Few individually based studies have been performed. Using data from the Norwegian Prescription Database, this study investigated the individual level effect of prescribed cannabis extract (Sativex®) in prescription opioid users on their opioid use in the following year. Looking at all those filling a prescription for Sativex®, opioid use was only marginally lowered in the follow‐up period. Some Sativex® users, however, filled more prescriptions for Sativex® and were able to reduce their opioid use substantially. Further studies are needed to elucidate more details on these patients, so as to know who can benefit from such cannabis‐based extracts in reducing their opioid use. [ABSTRACT FROM AUTHOR]

Pregabalin (Lyrica®) may have an anxiolytic effect. It has also been reported that the use of this drug helps prevent excessive use of benzodiazepines. The aim of the present study was to examine if pregabalin reduced the intake of benzodiazepines. In a pharmacoepidemiological study, we compared pregabalin to the older drug gabapentin (Neurontin®) in the Norwegian Prescription Database. The database has total capture of all prescribed drugs outside institutions. We identified all prescriptions for the two drugs for patients aged 18-69 years between 2004 and 2007. Patients were grouped as psychiatric patients, patients with epilepsy, patients with neuropathic pain or non-specified users. We measured the use of benzodiazepines 182 days before and after the initiation of treatment with pregabalin and gabapentin. Between 15% and 29% of the patients were able to stop using benzodiazepines after starting pregabalin or gabapentin treatment. Psychiatric patients who started pregabalin were able to reduce the amount of benzodiazepines used by 48%, compared to only 14% among starters of gabapentin. This study shows that some patients reduced their use of benzodiazepines substantially after starting pregabalin. [ABSTRACT FROM AUTHOR]