Spice / Synthetic Cannabinoids

Medically reviewed by Prof. Giorgi Pkhakadze, MD, MPH, PhD — GMJ Editorial Board

What is Spice / Synthetic Cannabinoids?

Spice, also known as K2 or synthetic cannabinoids, refers to a group of laboratory-made chemicals that are sprayed onto plant material and smoked, or sold as liquids to be vaporized in e-cigarettes. These substances are designed to mimic the effects of THC (delta-9-tetrahydrocannabinol), the psychoactive component in marijuana, but are chemically distinct and often much more dangerous.

Unlike natural cannabis, synthetic cannabinoids are continuously modified by manufacturers to evade legal restrictions, resulting in hundreds of different chemical compounds with unpredictable effects. Common street names include Spice, K2, Synthetic Marijuana, Fake Weed, and many branded products. These substances are often marketed as “legal highs” or “herbal incense,” misleadingly suggesting they are safe alternatives to marijuana.

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The Drug Enforcement Administration (DEA) has classified many synthetic cannabinoids as Schedule I controlled substances, making their manufacture, distribution, and possession illegal in the United States.

Health benefits & uses

Evidence grade: None

There are no established health benefits or legitimate medical uses for synthetic cannabinoids sold as Spice or K2. These substances are not approved by the FDA for any medical condition and lack the safety profile and controlled composition necessary for therapeutic use.

While some synthetic cannabinoids have been studied in laboratory settings for potential medical applications, the products sold illicitly bear no resemblance to pharmaceutical-grade compounds and contain unknown mixtures of chemicals with unpredictable effects.

How it works

Synthetic cannabinoids act on the same brain cell receptors as THC (cannabinoid receptors CB1 and CB2), but often bind more strongly and unpredictably. This can result in effects that are much more intense and dangerous than natural marijuana.

The chemicals in Spice products are full agonists at cannabinoid receptors, meaning they activate these receptors completely, whereas THC is only a partial agonist. This difference in receptor activation can lead to severe and life-threatening effects including seizures, kidney damage, and psychotic episodes.

The constantly changing chemical composition of these products means that users cannot predict the effects, potency, or safety of any given batch, making each use potentially dangerous.

Dosage

There is no safe or recommended dosage for synthetic cannabinoids. The composition and potency of these products are completely unknown and unregulated, making any use extremely dangerous.

Unlike pharmaceutical medications with established dosing guidelines, Spice products contain unknown quantities of unidentified chemicals that can vary dramatically between batches and even within the same package.

Medical professionals and public health authorities strongly advise against any use of these substances due to their unpredictable and potentially fatal effects.

Food sources

Synthetic cannabinoids are not found in any natural food sources. These are entirely artificial chemicals created in laboratories, often in unregulated facilities with no quality control or safety standards.

These substances are typically applied to dried plant material or sold as liquids, but they do not occur naturally in any plants, foods, or dietary sources.

Safety & side effects

Synthetic cannabinoids pose serious health risks and have been linked to numerous emergency department visits, hospitalizations, and deaths. Common adverse effects include:

• Severe agitation and anxiety
• Nausea and vomiting
• High blood pressure and rapid heart rate
• Seizures and tremors
• Hallucinations and psychotic episodes
• Kidney damage and acute kidney injury
• Stroke and heart attack
• Coma and death

These products may also be contaminated with heavy metals, pesticides, or other toxic substances due to unregulated manufacturing processes. The risk of overdose is extremely high because users cannot know the potency or composition of what they are consuming.

Interactions

Synthetic cannabinoids can interact dangerously with numerous medications and substances, including:

• Blood thinners (warfarin) – may increase bleeding risk
• Sedatives and depressants – can cause dangerous respiratory depression
• Heart medications – may cause dangerous changes in heart rhythm
• Psychiatric medications – can worsen mental health symptoms
• Alcohol and other drugs – unpredictable and potentially fatal interactions

Due to the unknown composition of these products, it is impossible to predict all potential interactions.

Who should be cautious

Everyone should avoid synthetic cannabinoids, but certain groups are at particularly high risk:

• Individuals with heart conditions or high blood pressure
• People with mental health disorders
• Those with kidney or liver disease
• Pregnant and breastfeeding women
• Adolescents and young adults
• Individuals taking any medications
• People with substance use disorders

Frequently asked questions

Are synthetic cannabinoids safer than marijuana?

No, synthetic cannabinoids are significantly more dangerous than natural marijuana. They bind more strongly to brain receptors and can cause severe, life-threatening effects that are rarely seen with natural cannabis.

Can synthetic cannabinoids be detected in drug tests?

Standard drug tests typically do not detect synthetic cannabinoids, though specialized tests are available. However, the constantly changing chemical composition makes detection challenging.

Is Spice legal?

Most synthetic cannabinoids are illegal under federal law as Schedule I controlled substances. However, manufacturers frequently modify the chemical structure to create new compounds that may temporarily evade specific legal restrictions.

What should I do if someone has a bad reaction to synthetic cannabinoids?

Call 911 immediately. Synthetic cannabinoid emergencies can be life-threatening and require immediate medical attention. Do not attempt to treat severe reactions at home.

Can you become addicted to synthetic cannabinoids?

Yes, regular use can lead to dependence and withdrawal symptoms including headaches, anxiety, depression, and irritability when use is stopped.