Toxicology Quiz on Substance Abuse

Toxicological Aspects of Substance Abuse

• Toxicology is the study of the harmful effects of toxins.
• It has both clinical and forensic applications.

Clinical vs. Forensic Toxicology

• Clinical toxicology focuses on emergency screening (e.g., overdose), toxic exposure, and therapeutic drug monitoring (TDM).
• Forensic toxicology focuses on postmortem examinations, criminal investigations, workplace drug testing, and sports doping.

Clinical Toxicology

• Requires no patient consent.
• Specimen identity is presumed.
• Screening results are sufficient for medical decisions.
• Results are used for medical evaluations.

Forensic Toxicology

• Subject consent is required.
• Specimen identity must be proven.
• Only confirmed positive results are considered valid.
• Results are used for legal action.

Analytical Problems in Toxicology

• Endogenous substances (e.g., cholesterol, fats, proteins), putrefactive amines are present in samples, making analysis complex
• Drug concentrations vary greatly, spanning over 100,000-fold.
• Some drugs cannot be easily detected.
• Analytical conditions may not be appropriate for all samples, some drug/poisons are unknown or very unusual.

Analytical Basis of Toxicology

• Immunoassay
• Chromatography (TLC, GC, HPLC)
• Mass spectrometry

Immunoassay

• Used for preliminary screening.
• An antibody-antigen reaction detects even small amounts of drugs/metabolites.
• Its specificity can be compromised by cross-reactivity.
• Examples include ELISA and RIA.

Immunoassay Disadvantages

• Specificity issues may result in false positives.
• Some drugs (e.g., NSAIDs) may produce false positive results when using cannabinoid detection methods.
• Some antihistamines may produce false positive reactions for amphetamines.
• Immunoassays are good screening tests, but not sufficient for confirmation.

Chromatography

• Separates mixtures based on the affinity between mobile and stationary phases.
• Commonly used with mass spectrometry for confirmation (e.g., GC/MS).
• GC/MS methods are considered gold standard for drug identification, often combined with immunoassays for reduced false negative results.

HPLC and Other Chromatography

• HPLC is primarily used for drugs difficult to vaporize or heat labile compounds.

GC (Gas Chromatography) vs. HPLC (High-Performance Liquid Chromatography)

GC/MS (Gas Chromatography/Mass Spectrometry)

• GC physically separates (purifies), and MS fingerprinting (identifies) the drug/chemical.
• The combination of GC and MS is a gold standard for accurate identification.
• These methods are chosen for substances difficult to volatilize.
• Results from a combination of assays are more reliable.

Mass Spectrometry

• Ionizes chemical samples and sorts ions based on mass-to-charge ratio.

Cocaine and Amphetamine

• Compounds are complex and their structural properties affect analysis.
• Characteristic fragments for definitive identification are needed.
• Presented in molecular structure and fragmentation for determination by mass/spectroscopy.
• Fragmentation patterns are characteristic of the drug, and used in mass spectrometry to accurately determine drug type.

Interpreting Test Results

• False Negatives: Drug is present but not detected e.g. due to a very low concentration or threshold is too high.
• False Positives: Drug is detected, but isn't present. This can happen due to interfering substances (like OTC meds or poppy seeds), cross reactions with reagents, or intentional sabotage.

National Poison Centre Mission

• Reduce poisoning mortality and morbidity by providing excellence, compassion, and innovation.
• Poisoning risk and occurrence reduction is aided by;
• optimizing poison treatment via information management.
• poison awareness and prevention via education.
• analyzing and interpreting lab results (for determination).

Test your knowledge on the toxicological aspects of substance abuse, focusing on clinical and forensic toxicology. Understand the differences between their applications and the challenges faced in analytical procedures. This quiz covers critical concepts that are essential for both medical and legal professionals.