K2: What Clinicians Need to Know

What is K2?

  • K2 refers to a wide variety of synthetic cannabinoids and other chemicals. They are sprayed on to shredded dried plant materials or sometimes paper.
  • It is not cannabis (weed) but is sometimes sold as an alternative to cannabis. The effects are rarely like cannabis so many people try it once but are disappointed.
  • K2 is popular in prison because of its potency, undetectability and availability.
  • "Jail paper" is a term used to describe paper laced with K2. This form has become increasingly popular as the paper can be soaked in liquid K2, dried, and then sent or shared with inmates as any other correspondence would be. Once an inmate receives jail paper they can tear it into small pieces, which can then be smoked or ingested to achieve a high.
  • The potency of K2 varies between and even within bags as there are hundreds of different synthetic cannabinoids used in K2 formulations.
  • K2 can have severe and unpredictable clinical implications due to its potent and unregulated nature.

Other Names

  • These products are wrapped in brightly colored packages and sold under a variety of brand names – K2 and Spice being the most recognizable.
  • K2 is also known as Green Giant, Potpourri, Bizarro, Geeked Up, Smacked, AK-4, 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.
Examples of K2 packaging.

Who Uses K2?

  • Use of K2 appears to be more common among men in their 20s and 30s.
  • Use is more common among low-income individuals, those who experience houselessness, and those in institutional settings like jails or prisons.

Why Do People Use K2?

  • K2 is cheaper and more accessible than other illicit drugs.
  • Powerful, intense, producing a potent and long-lasting effect.
  • Coping- for some. It may be used as a way of dealing with the difficult conditions of street life.
  • Feeling warm- Some users describe the drug making them feel warm, providing a brief respite from sleeping outdoors in cold weather.
  • Help with sleeping- K2 can act as a powerful sedative, which is used to help users sleep while in public or otherwise vulnerable environments.
  • Standard urine drug testing does not detect K2 in urine which, for people who fear the consequences of a positive drug test, is a reason to keep using K2. People use it to avoid detection in drug tests mandated for probation, housing programs, jobs, etc.

Clinical Implications:

Acute Effects and Toxicity

  • Neurological: K2 can cause a range of neurological effects, including agitation, confusion, dizziness, seizures, stroke, altered mental status and loss of consciousness.
  • Psychiatric: Users may experience hallucinations, delusions, psychosis, violent behavior, and suicidal thoughts.
  • Cardiovascular: Tachycardia or bradycardia, hypertension, chest pain, and heart attacks are among the potential cardiovascular effects.
  • Other Physical: Severe nausea and vomiting, rhabdomyolysis (muscle breakdown), kidney failure, and even death have been reported.
  • Unpredictability: The effects are unpredictable due to variations in chemical composition and potency, even within the same batch.

Withdrawal

  • Physical: Withdrawal symptoms can include rapid heart rate, chest pain, palpitations, difficulty breathing, headache, nausea, vomiting, and seizures.
  • Psychological: Users may experience severe anxiety, intense cravings, depression, irritability, nightmares, and hallucinations.
  • Severity: The severity of withdrawal symptoms may be linked to the duration and frequency of K2 use.

Serious Short-Term Symptoms

  • Violent behavior.
  • Increased heart rate
  • Suicidal tendencies
  • Repeated vomiting

Long-Term Effects

  • Unknown Long-Term Effects: The long-term effects of K2 use are not well understood due to the drug's relatively recent emergence.
  • Potential for Dependence: K2 can lead to physical and psychological dependence, making it difficult to quit.
  • Organ Damage: Some long-term consequences may include heart damage and renal damage.

Diagnosis

  • Diagnosing K2-related illness without a history of exposure is challenging. It is a clinical diagnosis, but it has no well-defined toxicological syndrome.
  • Because K2-related illness can present with altered mental status, consider it in the differential diagnosis of patients presenting with altered mental status with no other obvious explanation.
  • Given the constant changes to K2 chemical structures, we can continue to expect that patients will present with new and constantly changing signs and symptoms, which makes diagnosis and treatment challenging.

Clinical Management

  • Treatment is generally supportive. There is no specific antidote or antagonist.
  • Supportive treatment options include (as needed):
    • Intravenous fluids, supplemental oxygen, airway protection.
    • Anti-emetic medications.
    • Benzodiazepines (commonly used to treat agitation, combativeness, and muscular hyperactivity).
  • People who use K2 may also be dependent on opioids. If the initial presentation was decreased level of consciousness, they may have also received multiple doses of naloxone and be in withdrawal.

Harm Reduction Strategies for Patients

  • Avoid mixing K2 with other substances.
  • Start low and go slow (Take one hit and wait to see how it affects you before using more).
  • Avoid using alone (Use with someone or call the Never Use Alone Hotline).
  • Carry naloxone and use in case of suspected overdose.
  • Stay hydrated! Drink plenty of water before and during use.
  • Using safer smoking supplies, not sharing supplies and following other safer smoking practices helps to lower the chance of health issues.
  • Use in a safe environment with people you trust.

References

  • Trecki J, Gerona RR, Schwartz MD. Synthetic Cannabinoid – Related Illnesses and Deaths. N Engl J Med. 2015;373(2):103-107.
  • American Association of Poison Control Centers. (n.d.). Synthetic Cannabinoids. Retrieved from http://www.aapcc.org/alerts/synthetic-cannabinoids/
  • Brents LK, Prather PL. The K2/Spice Phenomenon: emergence, identification, legislation and metabolic characterization of synthetic cannabinoids in herbal incense products. Drug Metab Rev. 2014;46(1):72–85.
  • Kourouni I, Mourad B, Khouli H, Shapiro JM, Mathew JP. Critical Illness Secondary to Synthetic Cannabinoid Ingestion. JAMA Netw Open. 2020;3(7):208516. doi:10.1001/jamanetworkopen.2020.8516
  • Riederer AM, Campleman SL, Carlson RG, et al; Toxicology Investigators Consortium (ToxIC). Acute poisonings from synthetic cannabinoids: 50 U.S. Toxicology Investigators Consortium Registry Sites, 2010-2015.  MMWR Morb Mortal Wkly Rep. 2016;65(27):692-695.
  • Prete MM, Feitosa GTB, Ribeiro MAT, et al. Adverse clinical effects associated with the use of synthetic cannabinoids: A systematic review. Drug Alcohol Depend. 2025 Jul 1;272
  • Tait RJ, Caldicott D, Mountain D, Hill SL, Lenton S. A systematic review of adverse events arising from the use of synthetic cannabinoids and their associated treatment. Clin Toxicol (Phila). 2016;54(1):1-13.