Toxicological Aspects of Substance Abuse PDF

Toxicological aspects of substance abuse Dr Kaisan Mahadi  Toxicology Defined as study on harmful effects of toxins. Clinical VS Forensic. Clinical Forensic Emergency Screening Postmortem (eg: ove...

Toxicological aspects of substance abuse Dr Kaisan Mahadi  Toxicology Defined as study on harmful effects of toxins. Clinical VS Forensic. Clinical Forensic Emergency Screening Postmortem (eg: overdose) Criminal Toxic exposure Workplace drug testing Therapeutic drug Sports monitoring (TDM)  Clinical Forensic Patient consent not Subject must consent required to be tested Identity of specimen is Identity of specimen presumed must be proved Screening result is Only confirmed results sufficient for medical can be considered decision positive Results are used for Results are used for medical evaluation legal action What are the analytical problem  Immunoassay Analytical Chromatography Basis of (TLC, GC, HPLC) Toxicology Mass spectrometry  Immunoassay Used for preliminary screening Antibody – Antigen reaction à even a small amount of drug/metabolites can be detected. TAG Principles for immunoassay  The specificity detection might cross react and give a false positive reaction. – Cannabinoid detection developed to detect carboxylic acid metabolite. NSAID drugs (eg:ibuprofen and naproxyn) can give Disadvantages false positive result. – Codeine give positive reaction for morphine – Anti-histamines give positive reaction for amphetamines Good screening test, but not for confirmation.  ELISA Example Immunoassay RIA – radio immunoassay  Aims for separation of a mixture. Samples has affinity between mobile VS stationary phase. Gas chromatography + Mass spectrometry à gold Chromatography standard Typically, GC/MS preceded by rapid immunoassay to eliminate the majority of the negative samples.  Gas Chromatography The use of heat for vaporization is a “destructive process” à might change the chromatographic characteristics  High Performance Liquid Chromatography This method generally used for substances that are difficult to volatile (e.g. steroids) or heat-labile (e.g. benzodiazepines) GC VS HPLC for drug detection GC HPLC Destroys or burns the Using electrical or chemical in its chemical structure of detector to generate the compound. the signal. Mobile phase - gas Liquid Large sampling Low sampling High specificity High specificity Faster Slower  GC à physically separates (purifies) the compound MS à fingerprinting the drug/chemical These are usually referred as the GC/MS “gold standard”. The use of HPLC/MS à method of choice for substances that are difficult to volatilize.  Mass Spectrometry Ionizes chemical samples and sorts the ions based on their mass-to-charge ratio.  Interpretation of test results False negatives – Drug is present but not detected threshold too high quantity of drug in the specimen is too low Dilution False positives – Drug is detected when it doesn’t present Interfering substance present in the biological fluid, cross reacts with the reagents. Eg: OTC medications, herbal teas, poppy seeds, sabotages — Mission: "To reduce the mortality, morbidity, cost and occurrence of poisoning in a manner that strives for excellence, compassion and innovation”. — Via services: — to reduce the risk and occurrence of poisoning; — to encourage optimum treatment of poisoning cases by: — providing information on poisons and advice on managing poisoning cases; — conducting research and documentation of poisoning incidences; — coordinating and conducting poison awareness and prevention education; and, — carrying out analytical tests and interpretations of laboratory results. Thank You