Drug Detection and Analysis: A Comprehensive Guide
1. Introduction to Drugs and Their Effects
The World Health Organization (WHO) defines drugs as any substance introduced into the organism that may modify one or more biological functions. These substances can be addictive and lead to tolerance. This definition includes substances such as alcohol, caffeine, and nicotine. The WHO classifies clinical pictures of drug use under its medical diagnosis:
Acute Poisoning
A transient state following the ingestion or absorption of alcohol or a psychotropic substance that causes changes in the level of consciousness, emotional state, or other functions.
Dependence Syndrome
Physiological and behavioral manifestations in which the drug takes precedence over any other behavior for the individual.
Withdrawal
A group of symptoms with varying severity levels that occurs when there is absolute or relative withdrawal of a substance after repeated and prolonged use. Withdrawal may be accompanied by a state of delirium.
Psychotic Disorder
Symptoms resulting from the consumption of psychotropic substances, characterized by hallucinations, delusions, psychomotor abnormalities, and abnormal emotional states.
2. Pharmacology of Drugs
Drug pharmacology encompasses the following:
Route of Administration
How the drug is taken, such as swallowed, injected, snorted, or smoked.
Absorption Process
How the drug passes into the bloodstream.
Distribution
This process depends on the solubility of the drug and where its metabolism will take place.
Elimination
Elimination can occur in three ways:
- Through the bile
- Through feces
- Through the kidney (most common)
3. Analytical Techniques for Drugs of Abuse
Clinical laboratories analyze different biological samples to detect drug use. Drug abuse analytics involve two types of analysis:
- Initial screening
- Confirmation
The type of biological sample used depends on the analysis’s primary objective. Urine is often the preferred sample due to its non-invasive collection procedure and the higher concentration of drugs and their metabolites compared to serum. Blood samples are used to determine recent use and for forensic analysis.
Detection Time in Urine
- Amphetamines: 2 to 4 days after oral or injection administration.
- Cannabinoids: 1 to 36 days after oral or smoked administration.
- Cocaine: 3 days after inhalation or injection.
- Opiates: 2 to 5 days after oral, injection, or inhalation.
- Ethanol: The detection time depends on weight, age, and individual metabolism.
Alternative samples include saliva, hair (for long-term studies), blood, and tissue extracts for determining recent use (in blood) and post-mortem studies.
Screening Analysis
These tests aim to eliminate samples with negative results and minimize the number of samples requiring confirmatory analysis. Screening techniques are also known as presumptive techniques and allow for rapid assessment of an individual’s consumption profile. They are easy to perform and do not require specialized personnel.
Screening techniques are based on immunochemistry, particularly the principle of competition. This involves a commercial liner prepared in the laboratory (containing the marked drug substance) and the substance used by the individual, each competing to bind with a specific antibody.
Cut-off Concept
The cut-off refers to the threshold value of each test, representing the minimum concentration of the substance required for a positive result. A negative sample may still contain the substance but at a level below the cut-off. The cut-off must be higher than the technique’s sensitivity.
Confirmatory Analysis
Confirmatory analysis utilizes techniques such as:
- Gas Chromatography: The mobile phase consists of an inert gas (He, Ar, or N), and the stationary phase can be solid or liquid media.
- Mass Spectrometry: This technique separates mixed substances based on their behavior within a gas and then subjects them to a high-energy electron beam.
- High-Performance Liquid Chromatography (HPLC): The mobile phase consists of a liquid carrier, and the biological sample flows through a column under high pressure.
4. Methods for Detecting Major Drugs of Abuse
Cannabinoids
Detection techniques are based on the presence of metabolites like carboxy-tetrahydrocannabinol (THC). Samples used include urine, plasma, or whole blood.
Alcohol
Techniques are based on the reducing properties of alcohol. Samples used include urine, blood, expired air (breath), and saliva.
Opioids
Techniques require prior acid or enzymatic hydrolysis of the glucuronide. Samples include blood, plasma, saliva, urine, and sometimes hair.
Amphetamines
Techniques may have cross-reaction problems, leading to false positives. Samples used include blood and urine.
Cocaine
Techniques may have false negatives due to the instability of the substance in biological samples. Techniques are increasingly based on detecting metabolites. Samples used include blood and urine.