NATIONAL POISON CENTRE (NPC) WHO COLLABORATING CENTRE FOR DRUG - - PowerPoint PPT Presentation

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
• f 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
• verdose
• TDM
• Qualitative
• Acute poisoning
• No significant relation between concentration and poisoning effects e.g.

paraquat and most of chemicals 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. CAUTION !!

Sample

Sample Matrix Human Blood, serum, plasma, gastric lavage, urine, saliva, hair Environmental Water, soil, sediment Foods and drinks Tea, coffee, rice, milk, supplement, 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 Others stationery, passive sampler etc.

Blood Sample - Containers

Purple Lavender Light blue Green

ADDITIVE EDTA K2/K3 ACTION

• Erythrocytes, leukocytes (white blood cells)

and thrombocytes (platelets) are stable in EDTA anticoagulated blood for up to 24 hours.

• EDTA/ K2 tubes are used for testing whole

blood in the clinical laboratory. centrifugation for EDTA K2/gel tubes should be done within 6 hours after blood collection for best results.

• Mid- term storage (up to 2 weeks) in

primary tubes is recommended at –20°C. ADDITIVE Sodium Citrate either 3.2% or 3.8% Citrate, theophylline, adenosine, dipyridamole (CTAD) ACTION

• These tubes MUST BE COMPLETELY

FILLED due to the amount of additive in the tube. Short draw tubes will be rejected.

• Clinical laboratory performs various tests on

citrate-anticoagulated blood specimens to determine coagulation disorders and to monitor patients receiving anticoagulation therapy such as heparin, coumarin or warfarin ADDITIVE Sodium Heparin, Lithium Heparin Ammonium Heparin ACTION

• The interior of the tube wall is coated with

lithium heparin, ammonium heparin or sodium heparin.

• The anticoagulant heparin activates

antithrombins, thus blocking the coagulation cascade and producing a whole blood / plasma sample instead of clotted blood plus serum.

• Plasma separator tubes (PST) are tubes

with lithium heparin and gel contain a barrier gel in the tube.

Pharmaceuticals

Compounds Sample Half life Time of Sampling Metabolism Instruments PCM Blood / Urine 3-7 hours 4-16 hours after ingestion. NAPQI Immunoassay, GC, LC

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 / Urine 2.4 to 19 hours Elimination half life increase with dose Parent compound can be detected, salicyluric acid , salicyl phenolic Immunoassay, GC, LC

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 Sampling Metabolism Instruments Benzodiazepin es

• e.g.

Alprazolam, lorazepam, midazolam, clobazam Blood / Urine Vary according to compounds (2-40 hours) Depend on compounds Parent compound can be detected. All drugs undergo metabolism process. Immunoassay, GC, LC.

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 40-50 minutes. Benzoylecgonine 4.7 hours Benzoylecgonine is measurable in urine within 1 to 4 hours and persists for up to 144 hours Major metabolite: benzoylecgonine and ecgonine methyl ester GC, LC, Immunoassays

Blood or plasma cocaine levels are not clinically useful for guiding therapy

Heroin Blood / Urine 60 to 90 minutes In overdose, heroin may be detected for as long as 36 hours 5-10 minutes metabolise to monoacetylmorphine and further metabolise to morphine GC, LC, Immunoassays

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 Sampling Metabolism Instruments Anticoagulants

• Warfarin,

coumarins and indandiones (chlorophacinone, diphacinone) PT/INR is a reliable test for absorption of physiologically significant doses. 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 Sampling Metabolism Instruments Pyrethroids

• Type I e.g.

permethrin

• Type II e.g.

cypermethrin, fenvalerate Blood / Urine Rapidly metabolized in mammals to their inactive acid and alcohol components e.g. Cyfluthrin half life 6.4 hours ASAP after exposure Metabolites: chrysanthemumic acid and alcohol . No parent compound GC, LC

Pyrethroids metabolite can be measured but not routinely available for the acutely poisoned patient.

Organophosphates

• Chlorpyrifos,

Malathion, diazinon, temephos. Blood / Urine Malathion 3 hours Chlorpyrifos 2 – 5 hours ASAP after exposure Metabolites: Alkyl

• phosphate. No parent

compound. GC, LC

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

• rganophosphate.

Insecticides

Compounds Sample Half life Time of Sampling Metabolism Instruments N-methyl Carbamate Blood / Urine N-METHYL CARBAMATES - Rapidly excreted. Aldicarb were eliminated in the urine over 74 hours Depend on compounds Metabolites depends on compound e.g. alpha-naphthol from Carbaryl, isopropoxyphenol from propoxur , carbofuran phenol from Carbofuran, aldicarb sulfone, sulfoxide and nitrile from aldicarb GC,LC. 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 compounds. METHOXYCHLOR rapidly metabolized and eliminated. Sample should be collected shortly after exposure (i.e., within 24 hours) Depend on compounds Vary according to compound* Some parent compound can still be detected. GC, LC.

Herbicides

Compounds Sample Half life Time of Sampling Metabolism Instruments Chlophenoxy Compounds

• 2,4-D, 2,4-DP,

MCPP, 2,4-DB Blood / Urine Complete excreted in 24-72 hours ASAP after exposure 90% Eliminated unchanged GCMS, LCMS,HPLC

Plasma chlorophenoxy herbicide levels appear to be poorly correlated with clinical effects

Paraquat Urine 80 to 90% excreted within 6 hours, almost 100% in 24 hours ASAP after exposure Parent compound can be measured in blood/urine

• Colorimetric test
• Spectrophotometric,

GC, LC and radioimmunoassay methods

Positive predictive value for death was quite high, the ability to predict survival was much lower.

Glyphosate Blood / Urine 3.1 hours. ASAP after exposure Undergo minimal metabolism, almost 100% body burden from parent compound

GC, LC, NMR Serum and urine glyphosate concentrations can be measured but are not clinically useful in guiding therapy.

Other Pesticides

Compounds Sample Half life Time of Sampling Metabolism Instruments PCP plasma, urine and adipose tissue 72-83 Hours

• na

primarily unchanged 80% excreted in urine GC If poisoning is suspected on the basis of exposure, symptoms and signs, do not postpone treatment until diagnosis is confirmed Dinotrophenolic pesticides Blood 5 to 14 days

• na

Unmetabolised dinitrophenols can be identified. (other metabolites :Dinitrophenol and 2-amino-4- nitrophenol) Spectrophometry, GC, LC Parent drug can usually be detected in plasma and urine, but these values are of little use in the acute management of the poisoned patient. Data on exposure and systemic levels of compounds in this group are limited.

Challenges

• Unknown poisoning in acute poisoning.

– Laboratory analysis may take longer time to identify unknown compounds. – Easier and faster to identify the compound according to external information sources : e.g. labels, purpose of use, suppliers, physical characteristics of the compounds. – Evaluation based on sign and symptom of exposure.

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