Dissertation (MSc Chemistry)There is an alarming prevalence of drug abuse worldwide. Often the consumers are not aware about the types of substances they are using and the interrelated risks. In recent years, new psychoactive substances appeared in the illicit market. It has been frequently reported that there is the presence of novel psychoactive substances, such as synthetic cathinones, cannabinoids and phenethylamines, which are known to be pharmacologically and toxicologically hazardous. The current study was set to deal with identification of novel psychoactive substances from drug abuse patients maintained by methadone therapy, Liquid Chromatography Fourier transform mass Spectrometry, followed by a post-run library matching was conducted for every sample with an in-house database containing over 300 novel compounds and known metabolites. Data acquisition was in MS/MS and full-scan modes and belonging to different chemical classes were identified. Screening for novel psychoactive substances in urine from patients revealed that designer cathinones were highly preferred (32.26 %) followed by designer cannabinoids (19.34 %) and fentanyl analogues were least preferred at (0.51 %). A prescription drug Gabapentin was detected from patients who already in methadone therapy (1.48 %) and from new patients (3.47 %). Prevalence level of opioids use was found to be significantly associated with age of patients (p = 0.0408) and duration of treatment (p = 0.0194) while sex (p =0.9204) found to be not significant predictor of prevalence level of opioids use. Study of drug abuse patterns revealed a high prevalence of multiple drug abuse among all study subjects regardless of their treatment status. Key words: New psychoactive substances, synthetic cathinones, cannabinoids and phenethylamines, pharmacologically, toxicologically hazardous and Liquid Chromatography Fourier transform mass Spectrometry.