William E. Schreiber - An Introduction to Testing for Drugs of Abuse

LC record available at https://lccn.loc.gov/2021058984

LC ebook record available at https://lccn.loc.gov/2021058985

Cover Design: Wiley

Cover Image: © luchschenF/Adobe, Kondor83/Shutterstock, Stephen Orsillo/ Shutterstock, monticello/Shutterstock

Toxicology is one of the most complex fields in laboratory medicine, and it is a frequent source of consultations. Doctors, nurses, patients, and other clients ask me a lot of questions about drug testing and what the results mean. Here are some examples.

Can passive exposure to marijuana smoke cause a positive test for cannabis?

Which drugs are detected by your amphetamine assay?

If my patient is taking oxycodone, why was the screening test for opiates negative?

How long can heroin be detected in a urine sample?

Could this level of cocaine in blood be fatal?

It has taken years to learn the answers and, perhaps more importantly, to locate the resources where those answers can be found. There is a huge literature on drugs of abuse and their measurement. However, it is hard to find a publication that summarizes both the testing process and the interpretation of test results. That is what laboratory and clinical practitioners need, and that is the subject of this book.

My goal is to provide a readable account of the most common drugs of abuse – what they are, how they work, therapeutic uses, potential for abuse, and how laboratories test for them. Enough practical information is included so that readers can understand and interpret the results of drug tests. The book is an introduction, not a compendium – more detailed information is available in textbooks, journal articles, and websites, some of which are listed at the end of each chapter.

Case studies are included with all of the chapters on drugs to add interest and bring the subject to life. Some of the cases describe real people and events, while others are the product of my imagination, often based on personal experiences or stories related by colleagues. Whether real or fictional, every case poses questions to the reader, discusses the answers to those questions, and ends with several key points about drug use and the role of testing. The cases include material that is not covered elsewhere – don't skip them!

This book was conceived and written with three audiences in mind. The first group includes pathologists, clinical laboratory scientists, and medical technologists. They are the professionals who perform drug testing, report the results, and provide consultation on what those results mean. A second group consists of physicians, nurses, pharmacists, and other healthcare providers who use test results in making decisions about patient management. The third audience is composed of trainees – residents in pathology and primary care specialties as well as students in medicine, pharmacy, nursing, and other health‐related programs.

I would like to acknowledge the contributions of others who have helped in the creation of this work. Dr Maria Issa and Dr Serguei Likhodi read portions of the manuscript and offered helpful feedback and suggestions. Kate Campbell produced most of the illustrations in the first section of the book, many of which describe the testing process. Finally, I salute the scientific and technical staff in the clinical laboratories of Vancouver General Hospital, the British Columbia Provincial Toxicology Centre, and LifeLabs. They have been my work colleagues for more than three decades and have taught me much of what I know about this field.

William E. Schreiber June 23, 2021

This is a book about drugs that affect mood, perception, and consciousness. Drugs can relax you, energize you, take away your pain, help you to sleep, or create feelings of euphoria. When taken in excess or for long periods of time, these same drugs can injure or kill you.

A drug is a substance that produces a change in biological function when consumed. If you look up the word “drug,” you are likely to see two types of definitions:

a substance intended for use in the diagnosis, cure, mitigation, treatment, or prevention of disease (Source: US Food and Drug Administration glossary of terms)

an illegal substance that some people smoke, inject, etc. for the physical and mental effects it has (Source: Oxford Advanced American Dictionary).

These definitions highlight the therapeutic properties of drugs on the one hand, and their potential for inappropriate use on the other.

Small amounts of a drug can have potent effects on the body. In most cases, those effects are mediated through binding of the drug to receptors that control cellular processes.

Drugs that affect the central nervous system act on neurons to increase or decrease the transmission of nerve impulses. Some drugs affect the flow of ions into and out of neurons, which changes their ability to initiate or propagate an action potential. Other drugs affect the release and reuptake of neurotransmitters, thereby stimulating or inhibiting communication between individual neurons.

Any drug can be used inappropriately. However, certain drugs are more prone to misuse than others because of their mood‐altering or intoxicating effects. These drugs activate the brain's reward system by stimulating the release of dopamine in several pathways. The sense of euphoria they produce is accompanied by other effects – feelings of energy and power in the case of stimulants, or relaxation and peace in the case of opioids.

The World Health Organization defines drug misuse as “Use of a substance for a purpose not consistent with legal or medical guidelines, as in the non‐medical use of prescription medications.” Drug or substance abuse refers to consumption of illicit drugs or to chronic use of a drug that interferes with a person's normal activities. It can involve illegal drugs purchased on the street (e.g., heroin), prescription drugs taken in excessive doses (e.g., benzodiazepines), or legal intoxicants (e.g., ethanol).

There is a blurry line between use and abuse for many drugs. When taking a substance causes harm, either to the individual or others, it can be considered substance abuse. Some of the consequences of drug abuse are:

mental/physical disabilities

long‐term health problems

risky behavior

not meeting responsibilities

altered social relationships.

A study published in The Lancet assessed the harm associated with 20 drugs that are commonly abused. The authors considered physical harm, dependence, and social harms to arrive at a mean score for each drug. Heroin and cocaine ranked first and second on the list of harmful drugs. In a subsequent article, the authors identified heroin, crack cocaine, and methamphetamine as the most harmful drugs to individuals and alcohol as the most harmful substance to others ( Figure 1.1).

The words drug and substance are both used in the medical community – they are generally equivalent in meaning. Substance is a broader term. It includes compounds that we may not consider to be drugs, such as alcohol, nicotine and caffeine, and it often appears in discussions of chemical dependency.

Figure 1.1 Graph comparing harm to users (x‐axis) vs harm to others (y‐axis) for 20 drugs and substances. Higher scores indicate a greater degree of harm. Drugs with the highest total scores are labeled. The points in the lower left corner of the graph represent (in order of decreasing harm to users) ketamine, benzodiazepines, mephedrone, methadone, butane, ecstasy, anabolic steroids, khat, LSD, mushrooms, and buprenorphine. The overall scores for each drug were based on assessments of 16 harm criteria.