Toxicology Laboratory National Poison Centre, Universiti Sains Malaysia (USM), Penang, Malaysia. NATIONAL POISON CENTRE (NPC) WHO COLLABORATING CENTRE FOR DRUG INFORMATION CLEARING HOUSE FOR TOBACCO CONTROL
Toxicology Analysis: What and When to Measure? Azaharudin Awang Ahmad Pharmacist, National Poison Centre (NPC) BPharm (Hons) USM, MSc Ana. Toxicology King’s College
Introduction • Detection, identification, and measurement of foreign compounds in biological and other specimens. • Methods are available for a very wide range of compounds e.g. - chemicals - pesticides - pharmaceuticals - drugs of abuse - natural toxins etc.
Introduction – Importance of Analytical Toxicology • Assist in the diagnosis, management, prognosis, and prevention of poisoning. • In research - determining the pharmacokinetic and toxicokinetic properties of substances or the efficacy of new treatment regimens. • Other activities - assessment of exposure following chemical incidents, therapeutic drug monitoring, forensic analyses, and monitoring for drugs of abuse.
Scope of Toxicological Analysis • Analyses are typically conducted in two phases Presumptive analysis Providing indications whether a particular drug or drug class is present. Subjected to confirmation analysis. Confirmation analysis Providing more definitive identification of the substances that may be present. Conducted with methods that have greater specificity which may examine the chemical structure of each substance as a means of identifying them. Laboratory Instruments e.g. LCMS, LCMS/MS,GCMS, GCMS/MS
Scope of Toxicological Analysis • Qualitative and quantitative analyses • Qualitative analyses - intended to identify particular substances in a specimen. • Quantitative analyses - intended to both identify particular substances and to establish how much is present in a specimen.
Consideration: Qualitative or Quantitative ? • Quantitative - Chronic exposure/poisoning - Significant relation between concentration and poisoning effects e.g. PCM overdose - TDM • Qualitative - Acute poisoning - No significant relation between concentration and poisoning effects e.g. paraquat and most of chemicals CAUTION !! If strong clinical indications of acute poisoning are present, treat patient immediately. Do not wait for laboratory confirmation, which can take days. Initial medical care should be based on clinical presentations.
Sample Sample Matrix Human Blood, serum, plasma, gastric lavage, urine, saliva, hair Environmental Water, soil, sediment Tea, coffee, rice, milk, supplement, Foods and drinks sugar etc Chemical products Fertilizer, poisons, plastic, PVC pipe dll. Animal and insects Fish, puffers, insects Cosmetics Cream, toner, syampoo etc Plants Leaves, fruits, mushroom, bird nest Pharmaceuticals and herbs Medicine, herbs, tablet, capsule etc stationery, passive sampler etc. Others
Blood Sample - Containers Purple Lavender Light blue Green ADDITIVE Sodium Citrate either 3.2% or ADDITIVE EDTA K2/K3 ADDITIVE Sodium Heparin, Lithium Heparin 3.8% Citrate, theophylline, adenosine, Ammonium Heparin ACTION dipyridamole (CTAD) ACTION • Erythrocytes, leukocytes (white blood cells) ACTION • The interior of the tube wall is coated with and thrombocytes (platelets) are stable in lithium heparin, ammonium heparin or EDTA anticoagulated blood for up to 24 • These tubes MUST BE COMPLETELY sodium heparin. hours. FILLED due to the amount of additive in the tube. Short draw tubes will be rejected. • The anticoagulant heparin activates • EDTA/ K2 tubes are used for testing whole antithrombins, thus blocking the coagulation blood in the clinical laboratory. • Clinical laboratory performs various tests on cascade and producing a whole blood / centrifugation for EDTA K2/gel tubes should citrate-anticoagulated blood specimens to plasma sample instead of clotted blood plus be done within 6 hours after blood collection determine coagulation disorders and to serum. for best results. monitor patients receiving anticoagulation therapy such as heparin, coumarin or • Plasma separator tubes (PST) are tubes • Mid- term storage (up to 2 weeks) in warfarin with lithium heparin and gel contain a primary tubes is recommended at – 20°C. barrier gel in the tube.
Pharmaceuticals Compounds Sample Half life Time of Metabolism Instruments Sampling PCM Blood / 3-7 hours 4-16 hours NAPQI Immunoassay, Urine after GC, LC ingestion. Acetaminophen levels obtained 4 to 16 hours after ingestion are most predictive of potential hepatotoxicity. After 24 hours, monitor liver enzyme to asses hepatotoxicity Salicylates Blood / 2.4 to 19 hours Parent Immunoassay, Urine Elimination half compound can GC, LC life increase be detected, with dose salicyluric acid , salicyl phenolic Toxicity should be assessed by serial salicylate levels, determination of acid base status every 2 hours, as well as, clinical evaluation to determine the severity of an exposure
Pharmaceuticals Compounds Sample Half life Time of Metabolism Instruments Sampling Benzodiazepin Blood / Vary according Depend on Parent compound Immunoassay, es Urine to compounds compounds can be detected. GC, LC. - e.g. (2-40 hours) All drugs undergo Alprazolam, metabolism lorazepam, process. midazolam, clobazam Qualitative testing for presence of benzodiazepine is helpful to confirm presence, especially when overdose history is sketchy. Quantitative levels are not usually clinically useful.
Substances of Abuse Compounds Sample Half life Time of Sampling Metabolism Instruments Cocaine Blood / Urine Parent Compound Benzoylecgonine Major metabolite: GC, LC, Immunoassays 40-50 minutes. is measurable in benzoylecgonine and urine within 1 to ecgonine methyl ester Benzoylecgonine 4 hours and 4.7 hours persists for up to 144 hours Blood or plasma cocaine levels are not clinically useful for guiding therapy Heroin Blood / Urine 60 to 90 minutes In overdose, 5-10 minutes GC, LC, Immunoassays heroin may be metabolise to detected for as monoacetylmorphine long as 36 hours and further metabolise to morphine Opioid plasma levels are not clinically useful or readily available. Urine toxicology screens may confirm exposure, but are rarely useful in guiding therapy
Rodenticides Compounds Sample Half life Time of Metabolism Instruments Sampling Anticoagulants PT/INR is a reliable test for absorption of physiologically significant doses. -Warfarin, coumarins and indandiones (chlorophacinone, diphacinone) Blood levels of the second-generation anticoagulants e.g. brodifacoum can be measured but the test is not immediately available, nor does it aid in immediate treatment decisions as does the PT or INR Zinc Phosphide Phosphides sometimes impart a foul rotten fish odor to vomitus, feces, and the breath. Toxicity is secondary to the release of phosphine gas on contact with moisture or moist air. Unlikely to trap gas in poisoniong case.
Insecticides Compounds Sample Half life Time of Metabolism Instruments Sampling Pyrethroids Blood / Urine Rapidly metabolized ASAP after Metabolites: GC, LC -Type I e.g. in mammals to their exposure chrysanthemumic acid permethrin inactive acid and and alcohol . No parent -Type II e.g. alcohol components compound cypermethrin, e.g. Cyfluthrin half fenvalerate life 6.4 hours Pyrethroids metabolite can be measured but not routinely available for the acutely poisoned patient. Organophosphates Blood / Urine Malathion 3 hours ASAP after Metabolites: Alkyl GC, LC -Chlorpyrifos, Chlorpyrifos 2 – 5 exposure phosphate. No parent Malathion, hours compound. diazinon, temephos. Measure plasma butyrylcholinesterase (pseudocholinesterase) and red blood cell (RBC) AChE levels. Depressions of plasma pseudocholinesterase and/or RBC acetylcholinersterase enzyme activities are generally available biochemical indicators of excessive organophosphate absorption. Enzyme depression is usually apparent within a few minutes or hours of significant absorption of organophosphate.
Insecticides Compounds Sample Half life Time of Metabolism Instruments Sampling N-methyl Carbamate Blood / Urine N-METHYL Depend on Metabolites depends on GC,LC. CARBAMATES - compounds compound Rapidly excreted. e.g. alpha-naphthol from Carbaryl, Aldicarb were isopropoxyphenol from eliminated in the propoxur urine over 74 hours , carbofuran phenol from Carbofuran, aldicarb sulfone, sulfoxide and nitrile from aldicarb These complex analyses, when available, can be useful in identifying the responsible agent and following the course of carbamate disposition. Quantification analysis unnecessary. Organochlorine Blood / Urine Vary according to Depend on Vary according to GC, LC. compounds. compounds compound* METHOXYCHLOR rapidly metabolized Some parent compound and eliminated. can still be detected. Sample should be collected shortly after exposure (i.e., within 24 hours)
Recommend
More recommend
