Background: There is a potential drug interaction between linezolid and antidepressants resulting in serotonin syndrome. Thus, clinicians often avoid this drug combination. However, little empirical data exists to support this avoidance. The objective of this study was to describe the risk of serotonin syndrome in patients receiving linezolid and how this risk changed with concomitant antidepressant use. Methods: A population based retrospective cohort study was conducted using the administrative databases at ICES. The patient population consisted of outpatients aged 66 years or older who were prescribed oral linezolid of any duration from 2014 to 2021 in Ontario, Canada. Patients who were also taking antidepressants during linezolid treatment were compared to patients not on antidepressants during linezolid treatment. The primary outcome was clinically significant serotonin syndrome requiring emergency room visit or hospitalization based on physician diagnosis, Sternbach criteria or Hunter criteria within 30 days of starting linezolid. Secondary outcomes included altered mental status, hospitalization and death due to any cause within 30 days. Results: Of 1,134 patients who were prescribed linezolid, 215 (19.0%) patients were also taking antidepressants. Less than 6 (<0.5%) patients had serotonin syndrome. The proportion of patients with serotonin syndrome was numerically lower in the antidepressant group. In a propensity score matched cohort, the adjusted risk difference for serotonin syndrome in the antidepressant group minus the no antidepressant group was -1.2% (95% CI -2.9% to 0.5%). The risk of altered mental status, hospitalization and death were similar between the two groups. Conclusions: The risk of serotonin syndrome was low in patients taking linezolid. Concurrent antidepressants did not significantly increase the risk of serotonin syndrome. These findings suggest that linezolid can be safely used in patients also on antidepressants when indicated. / Thesis / Master of Science (MSc) / Linezolid is an antibiotic that can potentially cause serotonin syndrome as an adverse effect when combined with antidepressants. In serotonin syndrome, dysfunction of the nervous system leads to a variety of symptoms that can be life threatening. This study examined people in Ontario aged 66 years or older who were prescribed linezolid from 2014 to 2021 to describe the risk of serotonin syndrome due to linezolid and how antidepressants change this risk. Patients were followed for 30 days from start of linezolid treatment to determine if they had serotonin syndrome based on diagnoses in emergency room or hospital visit records. Of 1,134 patients in the study, 215 (19.0%) patients took antidepressants. The risk of serotonin syndrome was low at less than 0.5%. This risk was not significantly different in patients on antidepressants when compared to those who were not. Therefore, linezolid is likely safe for patients receiving antidepressants.

Objective: This research aimed at reviewing the information provided by the online drug misuse communities with reference to the available evidence-based literature on the novel psychoactive substances. Methodology: Among hundreds of novel psychoactive substances, four groups (phenethylamines, tryptamines, piperazines and miscellaneous) were selected for the study. Various website drug fora were identified by Google and Yahoo search engines using a set of specific key words. The methods consisted of extracting and analysing qualitative data from the identified website fora. This was also supplemented by critical reviewing the existing evidence-based literature search for each of the selected psychoactive compounds. Results: The combined search results identified 84 unique website fora from which qualitative data were extracted for thirty novel psychoactive substances and organised into technical folders. This data extracted from online communities has thrown some light on factors such as the mode of purchase, subjective experiences, reasons for use, combinations, legislation, mechanisms of action in the CNS, side effects, toxicity and its management. This would enable the clinicians to be obtain full history when assessing and would inform better treatment choices. Conclusions: A range of novel psychoactive substances have been made recently available across the globe. The sale is easily achieved through the Internet. New legislations are made to control some recreational substances whilst newer substances appear. Furthermore, the distributors sell the backlog of products even after controlling of the substance has occured and hence are liable to potentiating criminal investigations. It is here suggested as well that the 'genuinity' of each onlince susbtance is questionable. Evidence-based literature is scant for the vast majority of these substances. Accidental overdoses are common occurences and some of the potential life-threatening clinical situations include sympathomimetic toxidrome and serotonin syndrome. Benzodiazepines appear to help with agitation and neuropsychiatric manifestations. Better levels of international cooperation and rapid share of available information may be needed to tackle the emerging problem of the novel psychoactive substances.