Cannabis for medical purposes: General information

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On this page

• Caution
• About cannabis for medical purposes
• Possible medical uses
• Active substances in cannabis
• Effects of cannabis
• Situations when you should not take cannabis
• Substances that may interact with cannabis
• Scientific references

Caution

This information applies to legal cannabis products produced and sold in Canada. These products have not:

• been reviewed by Health Canada to determine if they’re safe or effective to treat specific diseases or symptoms
• been authorized to treat specific diseases or symptoms

Cannabis use involves health risks. We don’t yet know or fully understand all of these risks.

This information is for adults who use cannabis for medical purposes. It should be used along with medical advice from your health care provider. Always consult your health care provider before starting to use cannabis for medical purposes. Use extra caution when cannabis is being used by children for medical purposes. Please consult your child’s health care provider for guidance.

About cannabis for medical purposes

Before using cannabis for medical purposes, discuss this with your health care provider, especially if you:

• have any health issues
• aren’t sure how cannabis may affect you
• have a history of problems with substance use, including problematic alcohol use
• use prescription medications, over-the-counter medications, natural health products or other substances

Regular follow-up appointments with your health care provider are important to determine if you:

• need to change how much you use
• are experiencing benefits or harms from cannabis
• need to change the kind of cannabis products you use 

Possible medical uses

Health Canada hasn’t authorized the use of cannabis products to treat any specific diseases or symptoms. However, the available research, although limited, suggests that cannabis might relieve:

• symptoms associated with end-of-life care
• chronic non-cancer pain (mainly neuropathic)
• loss of appetite and weight loss associated with:
  • cancer
  • HIV/AIDS   
• pain and muscle spasms from multiple sclerosis (MS)
• seizures from treatment-resistant childhood epilepsies
• insomnia and depressed mood associated with chronic diseases
• severe cancer pain that doesn’t respond to conventional treatments
• severe nausea and vomiting from cancer chemotherapy that doesn’t respond to conventional treatments

Your health care provider might also suggest cannabis for other diseases or symptoms.

Active substances in cannabis

The cannabis plant contains more than 100 cannabinoids. Cannabinoids are substances unique to cannabis. They’re responsible for its many effects.

The 2 most well-known and abundant cannabinoids in the cannabis plant are:

• CBD (cannabidiol)
• THC (delta-9-tetrahydrocannabinol)

CBD doesn’t cause a “high” and isn’t addictive.

THC can:

• impair you
• cause a “high”
• lead to addiction

The cannabis plant also contains other cannabinoids, usually in much smaller amounts. However, products made from cannabis, such as edibles and extracts, may contain much larger amounts of these cannabinoids, including:

• CBN (cannabinol)
• CBG (cannabigerol)
• CBC (cannabichromene)
• THCV (tetrahydrocannabivarin)

Some of these cannabinoids may cause a "high" or other effects on the mind, including possibly unwanted effects.

More research will help us better understand these other cannabinoids and determine if they can:

• cause side effects
• relieve symptoms
• change the effects of THC and CBD

Learn more:

• Cannabis for medical purposes: Side effects

Effects of cannabis

THC and CBD act on specific organs in the body that regulate various functions such as:

• digestion
• reproduction
• inflammation
• perception of pain
• wake and sleep cycle
• immune system activity
• stress and emotional state
• heart rate and blood pressure
• thinking and nervous system activity

Situations when you should not take cannabis

Do not take cannabis if you’re:

• pregnant
• breastfeeding
• planning a pregnancy
• a male experiencing fertility challenges
• allergic to cannabis or any substances found in cannabis products
• under the age of 25 unless your health care provider says the benefits outweigh the harm it could cause to your developing brain
• living with:
  • liver disease
  • kidney disease
  • heart or blood vessel disease 
  • a personal or family history of:
    • psychosis
    • schizophrenia
    • other mental illnesses

Don’t smoke cannabis if you’re sensitive to smoke.

Don’t smoke or vape cannabis if you have asthma or lung disease.

Substances that may interact with cannabis

Tell your health care provider which substances you’re currently taking, including:

• natural health products
• prescription medications
• non-prescription medications

Cannabis may interact with:

• alcohol
• antipsychotics
• blood thinners  
• amphetamines
• Saint John’s Wort
• oral contraceptives
• immunosuppressants
• stomach acid inhibitors
• anti-seizure medications 
• certain heart medications
• antiretroviral medications
• mood stabilizing medications
• grapefruit and grapefruit juice
• oral antibiotic and antifungal medications  
• antidepressants and anti-anxiety medications
• illegal drugs such as cocaine and hallucinogens
• any health products which cause dizziness or drowsiness, such as:
  • tranquilizers
  • sleeping pills
  • some pain medications
  • some muscle relaxants
  • some allergy or cold medications
  • medications for bladder problems

Scientific references

Health Canada used the following references to develop this content:

• Details for: EPIDIOLEX (Health Canada)
• Cannabis and Breastfeeding. (Breastfeeding Medicine)
• Cannabis use during pregnancy: An update (Medicina (Kaunas)
• The marijuana, cannabinoids, and female reproductive system (J Appl Toxicol)
• Cannabis sativa: The unconventional "weed" allergen (Ann Allergy Asthma Immunol)
• Practical considerations in medical cannabis administration and dosing. (Eur J Intern Med)
• Information for health care professionals: Cannabis (marihuana, marijuana) and the cannabinoids (Health Canada)
• The medicinal use of cannabis and cannabinoids--an international cross-sectional survey on administration forms (J Psychoactive Drugs)
• Pharmacokinetics and tolerability of Delta9-THC-hemisuccinate in a suppository formulation as an alternative to capsules for the systemic delivery of Delta9-THC. (Med Cannabis Cannabinoids)