Pharmacokinetics
By Kevin Shanks, D-ABFT-FT
Pharmacokinetics (PK) is the study of what the body does to a substance. The word is derived from Greek – Pharmakon which means “drug” and kinetikos which means “moving”. PK consists of four areas – absorption, distribution, metabolism, and excretion. This is also known as ADME.
Instrumentation in the Drug Metabolism and Pharmacokinetics Lab “Equipment used in the DMPK Lab” by NIH-NCATS is licensed under CC PDM 1.0.
Absorption (A) is the process by which substances enter the bloodstream. Substances can enter the bloodstream through a wide variety of routes, including oral (by mouth), inhalation (lungs), intravenous (injected into a vein), intramuscular (injected into muscle), rectal (suppository), oral mucosa (under the tongue), intrathecal (spinal fluid), dermal (skin), ocular (eye), and intranasal (nose).
Distribution (D) refers to the transfer of a substance form one part of the body to another. When discussing PK, this usually refers to the movement of substance from the blood into the tissues of the body (liver, heart, kidney, brain, muscle, and fat). Some factors that influence distribution are lipophilicity, pH, and plasma protein binding.
Metabolism of Heroin (Diacetylmorphine) Chemical structures drawn by Kevin G. Shanks (2018)
Metabolism (M) is the process by which the substance is altered to facilitate the removal of it from the body. Most metabolism occurs in the liver, but it can also occur in the kidneys, lung, gastrointestinal tract, and blood. Examples of metabolism include deacetylation (heroin to 6-acetylmorphine to morphine), nitro reduction (clonazepam to 7-aminoclonazepam), N-dealkylation (amitriptyline to nortriptyline), deamination (chlordiazepoxide to demoxepam to nordiazepam), and ester hydrolysis (cocaine to benzoylecgonine), as well as glucuronidation (oxazepam to oxazepam glucuronide), sulfate formation (morphine to morphine sulfate), and glycine conjugation (salicylate to salicyluric acid)
Excretion (E) is the final removal of the substance or by products from the body. Excretion is most commonly done via the liver and kidneys, but can occur via the lungs, breast milk, feces, sweat, sebum, and semen.
PK can help answer questions such as ‘Are drugs involved in this incident?’, ‘How much substance did a living individual consume?’, or ‘When was a substance taken by an individual?’.
The larger question at hand in many cases regarding impairment, drug toxicity, or a substance’s role in cause of death involves a related area of pharmacology called pharmacodynamics (PD), which will be explored in a later blog post.
If you have any questions or concerns regarding the role of pharmacokinetics in your toxicology case, please reach out to our Axis Forensic Toxicology subject matter experts at [email protected].
References
Guidelines for the Interpretation of Analytical Toxicology Results. Disposition of Toxic Drugs and Chemicals in Man. Twelfth Edition. Randall C. Baselt. Biomedical Publications. Pages xxx-xlii. (2020).
Pharmacokinetics and Pharmacodynamics. Principles of Forensic Toxicology. Fourth Edition. Barry Levine. American Association for Clinical Chemistry (AACC). 2017. 77-93.
Introduction to Forensic Toxicology. Clarke’s Analytical Forensic Toxicology. Sue Jickells and Adam Negrusz. Pharmaceutical Press. Pages 1-12. (2008).
Postmortem Toxicology. Clarke’s Analytical Forensic Toxicology. Sue Jickells and Adam Negrusz. Pharmaceutical Press. Pages 191-218. (2008).
Postmortem Forensic Toxicology. Principles of Forensic Toxicology. Fourth Edition. Barry Levine. AACC, Inc. Pages 3-14. (2017).
Alcohol, Drugs, and Driving. Clarke’s Analytical Forensic Toxicology. Sue Jickells and Adam Negrusz. Pharmaceutical Press. Pages 299-322. (2008).
Human Performance Toxicology. Principles of Forensic Toxicology. Fourth Edition. Barry Levine. AACC, Inc. Pages 15-30. (2017).
- Published in General
Drug Primer: Fentanyl
Fentanyl was originally synthesized by Paul Janssen in 1960 and was initially marketed as Sublimaze® and used as a general anesthetic. In the mid-1990s, fentanyl was introduced to the pharmaceutical market as a transdermal patch and marketed as Duragesic®. The Actiq® transmucosal lollipop and Fentora® buccal tablet were introduced in the 2000s. Historically, fentanyl has been used to treat breakthrough pain and is used in pre-operation procedures as an analgesic and anesthetic. Fentanyl is considered a Schedule II controlled substance in the USA and is only available via physician’s prescription as a pharmaceutical.
Chemical structure of Fentanyl
Structure drawn by Kevin G. Shanks (2021)
The substance is a mu (µ) opioid agonist and is considered to be 100-200 times more potent than morphine and up to 40 times more potent that diacetylmorphine (heroin) as an analgesic. Fentanyl’s blood elimination half-life is 3-30 hours but is dependent on the route of administration. Its volume of distribution is 2.5-3.5 L/kg. Fentanyl is biotransformed to its primary metabolite, norfentanyl, via the cytochrome P450 enzyme system. Other metabolites include hydroxyfentanyl, hydroxynorfentanyl, and despropionylfentanyl (4-ANPP). Effects of fentanyl use are analgesia, drowsiness, dizziness, incoordination, weakness, and lethargy. Adverse effects in overdose are central nervous system depression, respiratory depression, seizure, hypotension, apnea, hypoxia, and death.
Metabolism of Fentanyl to Norfentanyl
Drawn by Kevin G. Shanks (2021)
Fentanyl appeared on the illicit drug market in the USA in the 1970s. Illicitly manufactured fentanyl (of a non-pharmaceutical origin) typically originates from China and other Asian countries and can also be ordered off the “dark web” – internet sites designed to peddle illicit materials. As fentanyl has become a common adulterant in street heroin, the Drug Enforcement Administration (DEA) has reported an explosion of fentanyl-related drug seizures in recent years. From 2010 to 2019, fentanyl detections increased by 16,990%. Since 2019, the numbers have grown larger.
Regional trends in fentanyl 2001 – 2019.
NFLIS Annual Drug Report, 2019.
The modern forensic toxicology laboratory monitors both fentanyl and norfentanyl in blood and urine specimens. Typical detection limits for both parent drug and metabolite in biological matrices are typically 0.1 – 0.5 ng/mL. The current scope of testing and reporting limits offered by Axis Forensic Toxicology can be found in the online test catalog https://axisfortox.com/test_catalog/.
References
Fentanyl. Disposition of Toxic Drugs and Chemicals in Man. Twelfth Edition. Randall C. Baselt. Biomedical Publications. Pages 844-847. (2020).
Opioids. Principles of Forensic Toxicology. Fourth Edition. Barry Levine. AACC, Inc. Pages 271-291 (2017).
National Forensic Laboratory Information System (NFLIS). Drug Enforcement Administration. Springfield, VA. https://www.deadiversion.usdoj.gov/nflis/index.html. (accessed April 15, 2021).
NFLIS Brief: Fentanyl, 2001-2015. U.S. Department of Justice, Drug Enforcement Administration – National Forensic Laboratory Information System (NFLIS). Springfield, VA. (2017).
- Published in Drug Classes
Novel Emerging Compounds Panel Update
By Matt Zollman, Director of Operations and Product Management
In the spirit of continual improvement, to provide the most relevant panels and tests in the industry, our products are periodically updated as new compounds emerge and older compounds cease to be relevant over the years. It is with that goal in mind that we announce an update to our 13710: Novel Emerging Compounds Panel. Beginning with orders placed on or after November 8th, 2021, the 13710: Novel Emerging Compounds Panel will include the following compounds, in addition to those already in the panel:
- AP-237
- Butonitazene
- Etonitazene
- Flunitazene
- Fluorofentanyl
Attached you will find our most recent publications for our 13710: Novel Emerging Compounds Panel (Panel Specifications). Additionally, you can always find the most recent publication for our panel offerings on our Test Catalog, found at www.axisfortox.com.
For specific questions regarding our tests or tests not found on our Test Catalog, please contact our Lab Client Support Team at [email protected].
We look forward to serving you.
- Published in Announcements
Day of the Dead 2021
From Phil Roberts, CEO
Today Axis celebrates The Day of the Dead!
Some history on this cultural and religious holiday…
The Day of the Dead (Spanish: Día de Muertos or Día de los Muertos) is a holiday celebrated from 31st October through 2nd of November inclusive, though other days, such as 6th November, may be included depending on the locality. It originated, in part, in Mexico, where it is mostly observed, but also in other places, especially by people of Mexican heritage elsewhere. Although associated with the Western Christian All Hallowtide observances of All Hallow’s Eve, All Saints’ Day and All Souls’ Day, it has a much less solemn tone and is portrayed as a holiday of joyful celebration rather than mourning. The multi-day holiday involves family and friends gathering to pay respects and to remember friends and family members who have died. These celebrations can take a humorous tone, as celebrants remember funny events and anecdotes about the departed.
All Souls’ Day, also known as the Commemoration of All the Faithful Departed and the Day of the Dead, is a day of prayer and remembrance for the souls of those who have died, which is observed by Roman Catholics and other Christian denominations. All Souls’ Day is often celebrated in Western Christianity; Saturday of Souls is a related tradition more frequently observed in Eastern Christianity. Practitioners of All Souls’ Day traditions often remember deceased loved ones in various ways on the day. Beliefs and practices associated with All Souls’ Day vary widely among Christian denominations.
At Axis you would see a few people dressed up, the office a little decorated, and holiday food.
Celebrating The Day of the Dead is an example of where Axis can emphasize the meaning and impact of Axis’ work. We are on mission when we help families with closure.
May today be a fond remembrance of a friend or family member no longer with us, and a celebration of the importance of your work!
- Published in Announcements
NAME 2021 Recap!
By Phil Roberts, CEO
It was terrific connecting in person this year in West Palm Beach!
Dr. George Behonick, Axis’ Lab Director and Chief Toxicologist, and Trevor Templin, Axis’ Operational Services Manager, and I enjoyed visiting with everyone.
Dr. Behonick presented Case Report: Detection of Novel Psychoactive Drugs in the Context of Fentanyl and Heroin Use. This poster, developed in conjunction with the Office of the Lake County, Indiana, Coroner, provides an example of the complexities of death investigation in light of the emergence of novel compounds. For a copy of the poster, please contact [email protected].
George Behonick presents Axis Case Report
It is always exciting to have the NAME and Axis Communities come together. Axis is proud to contribute to the good work of our NAME accredited Offices and NAME members!
- Published in Announcements
NAME 2021 Annual Meeting – October 15-19, 2021
Axis Forensic Toxicology is pleased to be attending the NAME 2021 Annual Meeting later this month in West Palm Beach, Florida.
Dr. Behonick, Axis’ Lab Director and Chief Toxicologist, will be presenting Case Report: Detection of Novel Psychoactive Drugs in the Context of Fentanyl and Heroin Use on Sunday, October 17 from 11:30 AM – 12:30 PM
We look forward to connecting with those from the Axis community who will be attending! Stop by booth #402 in the Exhibit Hall to say hello!
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- Published in Announcements
Axis Expert Joins Newly Formed Postmortem Toxicology Committee
We are pleased to announce that an Axis Forensic Toxicology subject matter expert has been appointed to a new Society of Forensic Toxicologists (SOFT) standing committee.
Axis Forensic Toxicology (2021)
https://axisfortox.com
Kevin Shanks, M.S., D-ABFT-FT has joined SOFT’s newly formed Postmortem Toxicology committee, which is comprised of 11 forensic professionals who have experience in postmortem toxicology, forensic pathology, and/or medicolegal death investigation from across the United States and Canada. The committee is holding its first official meeting during the 2021 Society of Forensic Toxicologists annual conference in Nashville, TN. Shanks is also a member of SOFT’s Young Forensic Toxicologists committee and Designer Drugs committee.
The mission of the Postmortem Toxicology committee is to serve as a resource for medicolegal professionals and to promote collaboration and communication between forensic toxicologists, forensic pathologists and coroners, medicolegal death investigators, and law enforcement to assist in the determination of cause and manner of death.
The Society of Forensic Toxicologists (SOFT), founded in 1970, is a professional organization for forensic toxicologists and chemists. The Society’s peer reviewed scientific journal is the Journal of Analytical Toxicology. The Society will hold its annual conference September 26th through October 1st, 2021, in Nashville, TN.
Society of Forensic Toxicologists (2021)
http://www.soft-tox.org
- Published in Announcements
National Forensic Science Week
By Phil Roberts, CEO
This week we join fellow forensic scientists across the county in observance of National Forensic Science Week!
What a wonderful opportunity to…
- Recognize the important role medical examiners, coroners, pathologists, death investigators, forensic nurses, and infant clinicians play
- Celebrate the use of proper forensic science
- Appreciate the complexity of medicolegal death investigations, drug facilitated crimes, and infant welfare protection throughout the nation
- Applaud the scientific and technical professionals that serve our communities in this vital role.
Watch for communication throughout the week as we recognize and celebrate together.
Axis is proud to walk alongside you with your casework, and to be your forensic toxicology partner!
- Published in Announcements
Postmortem Redistribution
by Kevin Shanks, M.S., D-ABFT-FT
Postmortem redistribution (PMR) is the phenomenon that occurs in blood drug concentrations after death as drug from anatomic sites of high drug concentration (e.g. organs such as the liver, lungs, and heart (myocardium)) is released to sites of lower drug concentration (e.g. the blood). This release may falsely elevate the drug concentration in blood surrounding the organs or from the central cavity.
Blood collected in test tubes for analysis.
Test Tubes with Blood” by biologycorner is licensed under CC BY-NC 2.0.
Substances that are alkaline (pH > 7.0), lipophilic, and have volumes of distribution (Vd) greater than 3 L/kg are more likely to undergo PMR. These substances include many commonly detected drugs such as tricyclic antidepressants (e.g. amitriptyline, nortriptyline), amphetamines (e.g. methamphetamine, amphetamine), and opioids (e.g. fentanyl, oxycodone).
The exact mechanism of PMR has not yet been identified, but changes in pH and protein structure after death are thought to also play a role in the phenomenon. Because of this phenomenon, the preferred anatomical sites of blood collection for toxicological analyses are peripheral sites such as the iliac or femoral veins. The site of blood collection is but one variable in the occurrence of PMR. Other factors influencing PMR include body storage temperature (the higher the temperature, the greater the potential for concentration change), the time between death and specimen collection (a longer lapsed time gives more potential for changes), the position of the body when found (blood may drain from centrally located sites to peripherally located sites), and medical intervention (stomach contents may be aspirated or blood may move from central to peripheral sites; drug may be released from traumatized tissue into blood).
Even as it has been studied for decades, PMR is a complex process and is still not fully understood, but the aforementioned factors are just some variables to be considered when interpreting toxicology’s role in a medical-legal death investigation.
If you have any questions or concerns regarding PMR’s role in a postmortem toxicology case, please reach out to our Axis Forensic Toxicology subject matter experts at [email protected].
References
- Barnhart FE, Bonnell HJ, Rossum KM. Postmortem Drug Redistribution. Forensic Sci Rev. 2001. Jul;13(2):101-129.
- Pelissier-Alicot AL, Gaulier JM, Champsaur P, Marquet P. Mechanisms Underlying Postmortem Redistribution of Drugs: A Review. J Anal Toxicol. 2003 Nov-Dec;27(8):533-544.
- Yarema MC, Becker CE. Key Concepts in Postmortem Drug Redistribution. Clin Toxicol (Phila). 2005;43(4):235-241.
- Postmortem Redistribution of Drugs. Principles of Forensic Toxicology. Fifth Edition. Fred S. Apple, Barry S. Levine, Sarah Kerrigan. Springer Nature Switzerland AG. 2020. 595-602.
- Published in General
Drug Primer: Marijuana
by Kevin Shanks, M.S., D-ABFT-FT
Marijuana, also known as cannabis, is a genus of annual flowering plants in the family Cannabaceae, and consists of the species, Cannabis sativa and Cannabis indica. The plants are native to Eastern Asia, but are cultivated all over the world. Cannabis is considered a Schedule I controlled substance by the United States Federal government, but it is legalized for medical use in 36 states and the District of Columbia (DC) and for recreational use in 18 states and DC.
Marijuana plant.
‘Legal Colorado Marijuana Grow” by Brett Levin Photography is licensed under CC BY 2.0.
The plant contains more than 500 different compounds. At least 113 of the compounds are classified as cannabinoids. The major cannabinoid is Delta-9-tetrahydrocannibinol (THC), but others include tetrahydrocannabinolic acid (THCA), cannabidiol (CBD), cannabigerol (CBG), cannabinol (CBN), and tetrahydrocannabinolic acid (THCA). Other compounds in the plant include terpenes, such as alpha-pinene, limonene, linalool, and myrcene.
Chemical Structure of Delta-9-THC
Structure drawn by Kevin G. Shanks (2021)
THC binds to the endocannabinoid system in the body. Cannabinoid receptor 1 (CB1) is primarily located in the brain and spinal cord, while cannabinoid receptor 2 (CB2) is found in the gastrointestinal system, the immune system, and the peripheral nervous system. THC binds to these receptors and acts as a partial agonist, which means it activates them, but only has partial ability to produce a maximal response.
THC’s effects will vary according to the dose consumed, the potency of the substance, the route of administration, and the individual’s use history with the substance. When inhaled via smoking the plant or vaping THC oil, effects typically occur within minutes and last for a few hours. If taken orally via an edible such as THC-infused gummy candy and cookies, effects normally take 30-90 minutes to occur and last for 4-6 hours. Effects on the body include drowsiness, relaxation, relaxed inhibitions, altered time, altered perception, impaired learning and memory, difficulty in concentration and thought formation, and euphoria. Physiological effects include dry mouth, increased appetite, red eyes, and tachycardia.
Cannabis Edibles.
“THC-Infused Gummies” by THCProductPhotos is licensed under CC BY-ND 2.0
THC is metabolized in the liver primarily by the CYP2C9, CYP2C19, CYP2D6, and CYP3A4 enzymes to hundreds of detectable metabolites, with the main metabolites being the pharmacologically active 11-hydroxy-THC (11-OH-THC) and the pharmacologically inactive 11-nor-9-carboxy-THC (THC-COOH). THC-COOH is further conjugated with glucuronic acid and then excreted out of the body via the feces and urine.
Detection windows for the metabolite can be quite extensive and will vary according to the dose used, duration of use, and the individual using the substance. Frequent users of THC could have detectable levels of THC-COOH in their urine for up to 30 days or longer after cessation of use. Most infrequent users eliminate the metabolite within a few days up to a week after use.
A forensic toxicology lab can test for THC using many different types of instrument platforms. The initial screening test can be an immunoassay test, but can also be completed via gas chromatography with mass spectrometry (GC-MS), liquid chromatography with high resolution mass spectrometry (LC-QToF-MS) or liquid chromatography with triple quadrupole mass spectrometry (LC-MS/MS). Confirmatory testing is usually completed by either GC-MS or LC-MS/MS. In blood, both parent THC and, at minimum, the THC-COOH metabolite is monitored. Normal reporting limits for blood testing are 0.5-1 ng/mL for THC and 1-10 ng/mL for THC-COOH. In urine, labs typically only monitor THC-COOH with reporting limits for positive determination varying widely (5-300 ng/mL). The current scope of testing and screening and confirmation reporting limits offered by Axis Forensic Toxicology can be found in the online test catalog.
References
- Tetrahydrocannabinol. Disposition of Toxic Drugs and Chemicals in Man. Twelfth Edition. Randall C. Baselt. Biomedical Publications. Pages 2041-2045. (2020).
- Cannabis. Principles of Forensic Toxicology. Fifth Edition. Marilyn A. Huestis, Barry S. Levine, Sarah Kerrigan. Springer Nature Switzerland AG. Pages 389-448 (2020).
- Published in Drug Classes