Spice and K2 (Synthetic Cannabinoids): Why the Effects Are Unpredictable, and How Treatment Works

Spice and K2 are two of the many brand names for synthetic cannabinoids. NIDA describes them as a class of lab-made substances that are chemically similar to chemicals in the cannabis plant, but that often produce stronger and very different effects [1][2]. The DEA says they are sold under the guise of herbal incense or potpourri, packaged with no information about their health and safety risks [3]. That last point is the whole page in one line. A person who uses them cannot know what is in the packet, and the federal record of what has been in the packet includes the anticoagulant used in rat poison [4].

This page is the hub for Spice and K2 on this site. It covers what synthetic cannabinoids are and how they are sold, why their effects cannot be predicted, and what a severe reaction looks like. It covers whether they are addictive and what withdrawal involves, as NIDA describes it. It covers whether they show up on a drug test, in the only form a federal source supports, and how treatment works. It names no amount and no schedule. Our hub on drug addiction covers the wider group of substances.

What Spice and K2 Are

Synthetic cannabinoids are not marijuana. NIDA’s definition is that they are a class of lab-made substances chemically similar to chemicals found in the cannabis plant, though they often produce stronger effects [1]. Some synthetic cannabinoids have potential or current medical uses, NIDA says, but many are illicitly manufactured and sold [2]. The illicit ones are usually added to the liquid cartridges used in vaping devices, or added to dried, shredded plant material so they can be smoked [1][2]. NIDA lists the drug as Schedule I [1].

The DEA describes the same products from the enforcement side. K2 and Spice are just two of the many trade names for synthetic designer drugs intended to mimic THC, the main psychoactive ingredient of marijuana [3]. They are from the synthetic cannabinoid class, and they are often marketed and sold as herbal incense or potpourri [3]. Spraying or mixing the chemicals onto plant material gives the most common route, smoking, in a pipe, a water pipe or rolled in paper. Liquid versions are made to be vaporized in disposable and reusable electronic cigarettes [3]. The DEA’s list of names runs from Spice and K2 through RedX Dawn, Paradise, Demon, Black Magic, Spike, Mr. Nice Guy, Ninja, Zohai, Dream, Genie, Sence, Smoke, Skunk, Serenity, Yucatan, Fire, Skooby Snax and Crazy Clown [3]. NIDA’s list is the same [1]. The names change faster than any page can track, and a new name is not a new drug.

Why the Effects Are Unpredictable

Three federal agencies say the same thing in three different ways. NIDA says the effects are similar to cannabis but stronger, and that the class often produces very different effects from the plant [1][2]. The DEA says the products are packaged without information as to their health and safety risks, and that state public health and poison centers have issued warnings in response to the adverse effects [3]. And the CDC has documented what can be in the packet.

In March 2018, the Illinois Department of Public Health was notified of patients arriving at emergency departments with unexplained bleeding and severely abnormal clotting tests, all of whom reported synthetic cannabinoid use in the previous three days [4]. The investigation, which included the CDC, identified 155 cases by late April, and four patients died from major bleeding [4]. The cause was brodifacoum, a long-acting vitamin K antagonist, the class of chemical used in rat poison, in the synthetic cannabinoid products [4]. Every patient reported bleeding from at least one site [4]. The CDC’s report is a surveillance record, not a study, and the figures in it are the CDC’s own.

That outbreak is the reason this page does not describe a typical high or a typical bad batch. There is no typical. The chemical in the packet changes from brand to brand and batch to batch, the amount is unknown, and the packet says nothing. A severe reaction is not evidence of an unlucky batch. It is evidence of the product class.

If someone is having a seizure, is unresponsive or has trouble breathing, call 911. For a mental-health crisis call or text 988.

Severe Reactions and Overdose: What to Watch For and What to Do

NIDA lists the effects a person may feel first: feeling relaxed, increased appetite, irritability and restlessness, anxiety, fear, distrust, panic and hallucinations [1]. Then it lists the health risks, which it says are similar to cannabis’s but more severe: increased heart rate and blood pressure, unconsciousness, tremors and seizures, nausea and vomiting, numbness and tingling, and death by heart attack or organ failure [1]. Synthetic cannabinoids, NIDA says, have also been involved in accidental overdose deaths [1]. If someone is having a seizure, is unresponsive or has trouble breathing, call 911. For a mental-health crisis call or text 988.

The DEA’s list, drawn from state health and poison-center warnings, overlaps and adds to it: fast heart rate, elevated blood pressure, unconsciousness, tremors, seizures, vomiting, hallucinations, agitation, anxiety, pallor, numbness and tingling [3]. In some instances, the DEA says, the adverse effects can be long-lasting even after the person stops using [3]. The CDC’s outbreak adds unexplained bleeding, most often blood in the urine, to the list of things that have sent people who used these products to an emergency department [4].

There is no reversal drug to name. What a hospital does for a severe reaction is supportive care for whatever the reaction is, and in the Illinois outbreak that meant plasma and vitamin K for the bleeding [4]. What a bystander does is simpler. A person who has used Spice or K2 and is having a seizure, cannot be woken, is struggling to breathe, or is bleeding without an injury needs an emergency department, and the emergency team needs to know a synthetic cannabinoid was involved.

If someone is having a seizure, is unresponsive or has trouble breathing, call 911. For a mental-health crisis call or text 988.

Are Synthetic Cannabinoids Addictive? Withdrawal as NIDA Describes It

Yes, in NIDA’s terms. People who use synthetic cannabinoids may develop a cannabis use disorder [1]. NIDA’s sentence on withdrawal carries its own hedge, and the hedge stays: withdrawal symptoms are similar to, but more severe than, those with cannabis, though more research is needed [1].

That means the list to start from is the cannabis one. NIDA’s withdrawal symptoms for cannabis are irritability, anger and aggression; feelings of nervousness and anxiety; restlessness; decreased appetite or weight; depression; insomnia or strange and unsettling dreams; nausea and vomiting; and abdominal pain [1]. For synthetic cannabinoids, NIDA says, expect the same shape, more severe, with the research still incomplete [1].

This page gives no onset, peak or duration for synthetic cannabinoid withdrawal. No federal source it cites publishes one, and the drug’s chemistry changes from packet to packet. Nor does the page name any medication for the withdrawal. The federal position on that is in the treatment section. Our hub on marijuana addiction covers the plant drug these products are compared with, and our overview of withdrawal symptoms covers how withdrawal compares across substances.

Do Spice and K2 Show Up on a Drug Test?

This is a question people ask about every drug, and the honest answer has to be given carefully. NIDA’s own sentence is that people have reported using these products because they were sometimes cheaper and more accessible alternatives to cannabis, and because they are mostly undetected by routine urine drug screens [2]. That is a statement about why people use them and about the harm that follows, not a recommendation, and it is carried here because a reader who thinks a negative test means a safe product needs to know the two things are unrelated.

The federal tables agree with NIDA. The federal workplace drug-testing rule at 49 CFR 40.85 lists nine analyte groups that laboratories must test for. The cannabis-related group is marijuana metabolites, the breakdown product of THC, and synthetic cannabinoids are not among the nine [6]. SAMHSA’s table of urine detection periods in TIP 47 has a cannabinoids row, and it is for cannabis; there is no row for synthetic cannabinoids [5]. So this page prints no window. Specialized tests for some synthetic cannabinoids exist, and because the chemicals keep changing, what a particular test can find is a question for whoever runs it. Our page on how long marijuana stays in your system covers the cannabis row.

Treatment for Spice and K2 Addiction

NIDA’s position is two sentences. There are currently no FDA-approved medications to treat cannabis use disorder. There are behavioral treatments for substance use disorders, such as cognitive behavioral therapy and contingency management [1]. NIDA’s treatment overview says the same for the class: for people with addictions to drugs like stimulants or cannabis, no medications are currently available to assist in treatment, so treatment consists of behavioral therapies, tailored to each patient’s drug use patterns and drug-related medical, mental and social problems [7].

NIDA describes what those therapies do. Behavioral therapies help people change their attitudes and behaviors around drug use, handle stress and triggers, and stay in treatment longer [7]. Cognitive-behavioral therapy helps people recognize, avoid and cope with the situations in which they are most likely to use. Contingency management uses rewards for staying drug-free and attending sessions. Motivational enhancement therapy works on readiness to change. Family therapy addresses the influences around a person’s use, especially for young people [7]. Our overview of the types of therapy and our page on cognitive behavioral therapy cover the same ground in more depth. Our overview of medication-assisted treatment explains what those medicines are for, and NIDA’s sentence above explains why none is approved here.

Two things are worth separating. A severe reaction to Spice or K2 is an emergency-room matter, and the section above is about that. Treatment for the addiction is what comes after, and it is usually not a detox. SAMHSA’s protocol says detoxification is not substance abuse treatment and rehabilitation, and that a detox program is not designed to resolve the longstanding psychological, social and behavioral problems associated with alcohol and drug use [8]. Our page on medical detox explains which substances need a managed withdrawal and why. Our guide to the levels of care sets out the five treatment levels. Our page on inpatient rehab describes the most structured of them, and our page on outpatient rehab describes the lighter end. NIDA’s warning that these products are involved in panic, distrust and hallucinations is one reason an assessment looks at mental health alongside the drug use [1].

The practical questions settle faster than people expect. Our page on how long rehab takes covers length of stay. Our page on how much rehab costs gives our own published price ranges by level of care. Our guide to insurance coverage covers what a plan decides. Our guide to the admissions process sets out what a program needs before it can give someone a date. Our page on what the rehab process is like walks through a stay. Our treatment center directory has a map you can browse by state.

Frequently Asked Questions

Sources

1. National Institute on Drug Abuse. (2025). Drugs A to Z — Synthetic Cannabinoids; Cannabis. National Institute on Drug Abuse. https://nida.nih.gov/research-topics/drugs-a-to-z
2. National Institute on Drug Abuse. (2023). Synthetic Cannabinoids (Research Topics — Highlights). National Institute on Drug Abuse. https://nida.nih.gov/research-topics/synthetic-cannabinoids
3. Drug Enforcement Administration. (2025). Spice/K2, Synthetic Marijuana — Drug Fact Sheet. U.S. Department of Justice. https://www.dea.gov/factsheets/spice-k2-synthetic-marijuana
4. Moritz, E., et al. (2018). Notes from the Field: Outbreak of Severe Illness Linked to the Vitamin K Antagonist Brodifacoum and Use of Synthetic Cannabinoids — Illinois, March–April 2018. MMWR Morbidity and Mortality Weekly Report 67(21), Centers for Disease Control and Prevention. https://www.cdc.gov/mmwr/volumes/67/wr/mm6721a4.htm
5. Center for Substance Abuse Treatment. (2006). Substance Abuse: Clinical Issues in Intensive Outpatient Treatment, TIP 47, Appendix B: Urine Collection and Testing Procedures and Alternative Methods for Monitoring Drug Use — Exhibit B-1. Substance Abuse and Mental Health Services Administration. https://www.ncbi.nlm.nih.gov/books/NBK64092/
6. Legal Information Institute, Cornell Law School. 49 CFR § 40.85 — What are the cutoff concentrations for urine drug tests? Electronic Code of Federal Regulations. https://www.law.cornell.edu/cfr/text/49/40.85
7. National Institute on Drug Abuse. (2020). Drugs, Brains, and Behavior: The Science of Addiction — Treatment and Recovery. National Institute on Drug Abuse. https://nida.nih.gov/publications/drugs-brains-behavior-science-addiction/treatment-recovery
8. Center for Substance Abuse Treatment. (2006). Detoxification and Substance Abuse Treatment, Chapter 1: Overview, Essential Concepts, and Definitions in Detoxification. Substance Abuse and Mental Health Services Administration. https://www.ncbi.nlm.nih.gov/books/NBK64119/

This page is for general information and is not medical advice. Only a licensed clinician who knows your history can tell you what is right for you. If you or someone you know is in immediate danger, call 911. For free, confidential support 24/7, call or text 988.

Author

Kevin Wandler, MD

Chief Medical Officer, The Recovery Village