TOXICOLOGY SCREENING

Using the toxicology laboratory To confirm or exclude toxic exposures in suspected individuals To confirm or exclude toxic exposures in suspected individuals To decide specific antidote or specific interventions to hasten elimination To decide specific antidote or specific interventions to hasten elimination Reassurance Reassurance For medico-legal reasons For medico-legal reasons

Collection of samples Urine Urine Specimen obtained before administration of any drugs Specimen obtained before administration of any drugs Usually 50ml sample without added preservative Usually 50ml sample without added preservative Drug metabolites in urine can be separated and detected by chromatographic techniques Drug metabolites in urine can be separated and detected by chromatographic techniques Stomach contents Stomach contents Sample includes vomit, gastric aspirate or stomach washings Sample includes vomit, gastric aspirate or stomach washings Very important to collect and send first sample of washing, at least 50ml, without added preservative Very important to collect and send first sample of washing, at least 50ml, without added preservative

Contd.. Blood Samples taken on admission include 10ml of heparinised blood, 2ml of fluorinated blood and 10ml of blood without preservative or anti-coagulant Samples taken on admission include 10ml of heparinised blood, 2ml of fluorinated blood and 10ml of blood without preservative or anti-coagulant Use of disinfectant swab should be avoided Use of disinfectant swab should be avoided Samples should be dispensed with great care Samples should be dispensed with great care Any drug administered for the treatment of poisoning must be reported to the lab Any drug administered for the treatment of poisoning must be reported to the lab

Toxicology assays recommended by the National Academy of Clinical Biochemists Serum Assays, Quantitative Urine Assays, Qualitative Acetaminophen Acetaminophen Carbamazepine Carbamazepine Cooximetry (carboxyhemoglobin, methemoglobin, oxygen saturation) Cooximetry (carboxyhemoglobin, methemoglobin, oxygen saturation) Digoxin Digoxin Ethanol Ethanol Iron (plus transferrin or unfilled iron- binding capacity) Iron (plus transferrin or unfilled iron- binding capacity) Lithium Lithium Phenobarbital Phenobarbital Salicylate Salicylate Theophylline Theophylline Valproic acid Valproic acid Amphetamines Amphetamines Barbiturates Barbiturates Cocaine Cocaine Opiates Opiates Propoxyphine Propoxyphine Phencyclidine Phencyclidine Tricyclic antidepressants Tricyclic antidepressants

Methods used Spot tests Spot tests Spectro chemical tests Spectro chemical tests Immuno assays Immuno assays Chromatography Chromatography Thin layer chromatography (TLC) Thin layer chromatography (TLC) High-performance liquid chromatography (HPLC) High-performance liquid chromatography (HPLC) Gas chromatography (GC) Gas chromatography (GC)

Chromatography Thin layer chromatography (TLC) is a chromatography technique used to separate mixtures. It involves a stationary phase consisting of a thin layer of adsorbent material, usually silica gel, aluminium oxide, or cellulose immobilized onto a flat, inert carrier sheet Thin layer chromatography (TLC) is a chromatography technique used to separate mixtures. It involves a stationary phase consisting of a thin layer of adsorbent material, usually silica gel, aluminium oxide, or cellulose immobilized onto a flat, inert carrier sheet Because of its simplicity and speed TLC is often used for monitoring chemical reactions and for the qualitative analysis of reaction products. Because of its simplicity and speed TLC is often used for monitoring chemical reactions and for the qualitative analysis of reaction products. A small spot of solution containing the sample is applied to a plate, about one centimetre from the base. The plate is then dipped in to a suitable solvent, such as ethanol or water, and placed in a sealed container. The solvent moves up the plate by capillary action and meets the sample mixture, which is dissolved and is carried up the plate by the solvent. Different compounds in the sample mixture travel at different rates due to the differences in their attraction to the stationary phase, and because of differences in solubility in the solvent. A small spot of solution containing the sample is applied to a plate, about one centimetre from the base. The plate is then dipped in to a suitable solvent, such as ethanol or water, and placed in a sealed container. The solvent moves up the plate by capillary action and meets the sample mixture, which is dissolved and is carried up the plate by the solvent. Different compounds in the sample mixture travel at different rates due to the differences in their attraction to the stationary phase, and because of differences in solubility in the solvent.

Tlc plate development sequence Thin layer chromatography Its wide range of uses include Its wide range of uses include assaying radiochemical purity of radiopharmaceuticals assaying radiochemical purity of radiopharmaceuticals determination of the pigments a plant contains determination of the pigments a plant contains detection of pesticides or insecticides in food detection of pesticides or insecticides in food analysing the dye composition of fibers in forensics, or analysing the dye composition of fibers in forensics, or identifying compounds present in a given substance identifying compounds present in a given substance

Bedside toxicology tests TestSubstrateDrug/poison Alcohol dehydrogenase Breath analysis Ferric chloride Meixner Microparticle agglutination Microparticle capture Oxalate crystals SalivaBreathUrineMushroomUrineUrineUrineEthanolCarbonmonoxideEthanol SalicylateAmatoxins Drugs of abuse Ethylene glycol

Ethanol concentration Testing is done using serum or plasma Testing is done using serum or plasma Concentrations are measured enzymatically using alcohol dehydrogenase Concentrations are measured enzymatically using alcohol dehydrogenase Larger lab measurements are done using GC assay Larger lab measurements are done using GC assay

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