Merck Manual

Please confirm that you are not located inside the Russian Federation

honeypot link

Cannabidiol (CBD)

By

Laura Shane-McWhorter

, PharmD, University of Utah College of Pharmacy

Last full review/revision Jan 2022| Content last modified Jan 2022
CLICK HERE FOR THE PROFESSIONAL VERSION

What is CBD?

Cannabidiol (CBD) is a chemical in the Cannabis sativa plant.

  • This plant, which contains more than 80 chemicals known as cannabinoids, is also called marijuana or hemp.

  • Two key ingredients in cannabis are tetrahydrocannabinol (THC) and CBD.

  • THC is responsible for the intoxicating effects of cannabis, and it might contribute to the plant's health benefits.

  • Unlike THC, CBD is not intoxicating,

  • Scientists believe that cannabinoids protect the cannabis plant itself from insects, bacteria, fungi, and environmental stressors.

  • CBD seems to prevent the breakdown of a chemical in the brain that helps control pain, mood, and mental function.

  • Some of these products contain CBD only, and others contain CBD in combination with other ingredients.

  • The labels of many products containing CBD make inaccurate claims about the amount of CBD in the product, and CBD concentrations in the same product sometimes vary. For example, one study found that only 31% of CBD products were accurately labeled; 43% contained more CBD than indicated on the label and 26% contained less than was indicated on the label. Moreover, THC (or marijuana) was found in 21% of the products.

What claims are made about CBD?

The only use of CBD generally recognized as safe and effective is treatment of certain seizure disorders. Seizure Disorders In seizure disorders, the brain's electrical activity is periodically disturbed, resulting in some degree of temporary brain dysfunction. Many people have unusual sensations just before... read more However, some people use CBD to treat many other health problems, including:

  • Bipolar disorder

  • Pain

  • Anxiety

  • Crohn disease

  • Diabetes

  • Sleep problems

  • Multiple sclerosis

  • Withdrawal from heroin, morphine, and other opioid drugs

Does CBD work?

Three studies have shown that a pure CBD product, available by prescription only, reduces seizures in adults and children with 2 rare forms of epilepsy. In these studies, people were treated with the CBD product for 14 weeks while they continued to take other antiseizure drugs. The CBD treatment decreased the numbers of seizures and reduced their frequency and severity.

Research on other health claims for CBD include studies in people that have been small and/or of poor quality.

What are the possible side effects of CBD?

CBD is probably safe to take by mouth or sprayed under the tongue. In studies, up to 1,500 mg of CBD taken by mouth for up to 4 weeks seemed reasonably safe. But CBD can have side effects, such as dry mouth, low blood pressure, diarrhea, decreased appetite, mood changes, light-headedness, and sleepiness.

  • CBD can injure the liver, especially if it is not used under medical supervision.

  • The contaminants in some CBD products could harm fetuses or infants, so CBD might not be safe for women who are pregnant or breastfeeding.

  • People with liver disease who use CBD might need to take lower doses than healthy people.

  • High doses of CBD might make tremors and other unwanted movements worse in people with Parkinson disease.

  • In studies in animals, CBD decreased sperm growth and development and reduced testicle size, so it might affect fertility in men.

  • Some CBD products are contaminated with solvents, including some that can cause cancer, as well as pesticides, heavy metals, bacteria, and fungi. Some of these contaminants could be harmful to a fetus.

  • A synthetic product sold in Utah has caused some acute poisonings.

What drug interactions occur with CBD?

CBD could speed up or slow down the body's breakdown of certain drugs and, therefore, decrease or increase levels of these drugs in the body.

Examples of drugs that may increase blood levels of CBD include the following:

  • Various drugs used to treat epilepsy (including brivaracetam, carbamazepine, clobazam, and topiramate)

  • Everolimus and tacrolimus, drugs used, for example, to prevent rejection after an organ transplant

  • Methadone (used to treat opioid addiction)

  • Other drugs, including amitriptyline (a tricyclic antidepressant sometimes used for treatment of chronic pain), warfarin (a blood thinner), omeprazole (a type of drug called a proton pump inhibitor, used to decrease production of stomach acid), nicotine, lithium (a mood stabilizer), and ketamine (an anesthetic occasionally used to treat depression)

CBD could interact in other ways with other drugs, such as

  • Sedatives, such as benzodiazepines, phenobarbital, and morphine, as well as alcohol: CBD can cause sleepiness and drowsiness, so taking both CBD and sedatives might make people too drowsy.

  • Phenytoin and rifampin: may lower the levels of CBD.

  • Levothyroxine, warfarin, and some antiseizure drugs: CBD may increase serum concentrations of these drugs, thereby intensifying and increasing their effects.

  • Valproic acid: Both valproic acid and CBD can cause liver injury, so the combination of CBD and valproic acid might increase the chance of liver injury.

Recommendations

A pure CBD product, available by prescription only, reduces the number of seizures as well as their severity and frequency in adults and children taking other antiseizure drugs for one of 2 rare forms of epilepsy.

Other effects of CBD have not been confirmed in high-quality studies in people.

CBD can have side effects, such as dry mouth, low blood pressure, diarrhea, decreased appetite, mood changes, light-headedness, and sleepiness. However, serious side effects are rare, and CBD is probably safe for most people.

  • Pregnant and breastfeeding women and people with liver disease, Parkinson disease, and men who want to have children should not take CBD.

  • Taking CBD while taking other medications that can cause drowsiness or while drinking alcohol can cause extreme drowsiness, which could be dangerous.

  • People who take drugs (including sedatives, antiseizure drugs, some antidepressants, valproic acid, and drugs to prevent the rejection of transplanted organs) should talk to their doctor before taking CBD.

  • The regulations about CBD are complicated and confusing. If a person chooses to take CBD, they should buy the product from a medical dispensary and look for a "Certificate of Authenticity."

Drugs Mentioned In This Article

Generic Name Select Brand Names
DURAMORPH PF, MS CONTIN
TEGRETOL
ONFI
TOPAMAX
AFINITOR
PROGRAF
DOLOPHINE
No US brand name
COUMADIN
PRILOSEC
COMMIT, NICORETTE, NICOTROL
LITHOBID
KETALAR
No US brand name
DILANTIN
RIFADIN, RIMACTANE
LEVOXYL, SYNTHROID
NOTE: This is the Consumer Version. DOCTORS: CLICK HERE FOR THE PROFESSIONAL VERSION
CLICK HERE FOR THE PROFESSIONAL VERSION
Others also read

Also of Interest

Download the Manuals App iOS ANDROID
Download the Manuals App iOS ANDROID
Download the Manuals App iOS ANDROID
TOP