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Drugs and Health Products

Consumer Information - Cannabis (Marihuana, marijuana)

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The courts in Canada have ruled that the federal government must provide reasonable access to a legal source of marijuana for medical purposes.

The legal sources of cannabis for medical purposes are licensed producers, personal production and designated production. A complete list of licensed producers can be found on the Health Canada website.

Cannabis is not an approved therapeutic product and the provision of this information should not be interpreted as an endorsement of the use of cannabis for therapeutic purposes, or of marijuana generally, by Health Canada. This leaflet is designed by Health Canada for patients authorized to possess cannabis for medical purposes. It is based on the document "Information for Health Care Professionals: Cannabis (marihuana, marijuana) and the Cannabinoids", and is a summary only - it will not provide you with all the facts about cannabis for medical purposes.

Contact your health care practitioner if you have any questions.

Serious Warnings and Precautions

Keep any fresh or dried marijuana and cannabis oil out of reach of children.
Cannabis (marihuana, marijuana) contains hundreds of substances, some of which can affect the proper functioning of the brain and central nervous system.
The use of this product involves risks to health, some of which may not be known or fully understood. Studies supporting the safety and efficacy of cannabis for therapeutic purposes are limited and do not meet the standard required by the Food and Drug Regulations for marketed drugs in Canada.
Smoking cannabis is not recommended. Do not smoke or vapourize cannabis in the presence of children.
Using cannabis or any cannabis product can impair your concentration, your ability to think and make decisions, and your reaction time and coordination. This can affect your motor skills, including your ability to drive. It can also increase anxiety and cause panic attacks, and in some cases cause paranoia and hallucinations.
Cognitive impairment may be greatly increased when cannabis is consumed along with alcohol or other drugs which affect the activity of the nervous system (e.g. opioids, sleeping pills, other psychoactive drugs).

About This Product

What the product may be used for

Your health care practitioner may have authorized the use of cannabis (marihuana, marijuana) for the relief of one or more of the following symptoms associated with a variety of disorders which have not responded to conventional medical treatments. These symptoms (or conditions) may include: severe refractory nausea and vomiting associated with cancer chemotherapy; loss of appetite and body weight in cancer patients and patients with HIV/AIDS; pain and muscle spasms associated with multiple sclerosis; chronic non-cancer pain (mainly neuropathic); severe refractory cancer-associated pain; insomnia and depressed mood associated with chronic diseases (HIV/AIDS, chronic non-cancer pain); and symptoms encountered in the palliative/end-of-life care setting. This is not an exhaustive list of symptoms or conditions for which cannabis may be authorized for use by your health care practitioner.

The potential therapeutic and adverse effects associated with cannabis use may vary depending on the amount of cannabis used and the concentration of cannabinoids in the cannabis product, the frequency of cannabis use, the patient's age and medical condition, previous experience with cannabis or cannabinoids, and the use of other prescription or non-prescription drugs. For more detailed information on potential therapeutic uses and adverse effects, please consult the "Information for Health Care Professionals: Cannabis (marihuana, marijuana) and the Cannabinoids".

What the active ingredients might be

  • Tetrahydrocannabinol (THC)
  • Cannabidiol (CBD)

The type and amount of these ingredients may vary depending on the cannabis strain.

What the other ingredients might be

There are over 70 different cannabinoids as well as hundreds of other chemicals in cannabis. Many of the chemicals found in tobacco smoke are also found in cannabis smoke.

What the product does

One of the principal active ingredients in cannabis (THC) acts on very specific targets found in the body known as cannabinoid receptors. Other cannabinoids, such as CBD, may also have targets other than the cannabinoid receptors. Cannabinoid receptors are found throughout the body, in most tissues and organs, but they are especially numerous in the brain and nervous system. Cannabinoid receptors are involved in the regulation of many bodily functions including: brain and nervous system activity, heart rate and blood pressure, digestion, inflammation, immune system activity, perception of pain, reproduction, wake/sleep cycle, regulation of stress and emotional state and many other functions. For more detailed information, please consult the "Information for Health Care Professionals: Cannabis (marihuana, marijuana) and the Cannabinoids".

When the product should not be used

Cannabis should not be used if you:

  • are under the age of 25
  • are allergic to any cannabinoid or to smoke
  • have serious liver, kidney, heart or lung disease
  • have a personal or family history of serious mental disorders such as schizophrenia, psychosis, depression, or bipolar disorder
  • are pregnant, are planning to get pregnant, or are breast-feeding
  • are a man who wishes to start a family
  • have a history of alcohol or drug abuse or substance dependence

Talk to your health care practitioner if you have any of these conditions. There may be other conditions where this product should not be used, but which are unknown due to limited scientific information.

Interactions with this Product

Cannabis may interact with several drugs. Make sure to tell your health care practitioner which prescription drugs, non-prescription drugs or herbal products you are currently taking, particularly:

  • Any drugs which slow down the central nervous system, causing drowsiness. These may include sleeping pills, tranquilizers, some pain medications, some allergy or cold medications, or anti-seizure medications.
  • Other drugs may include antiretroviral drugs used in the treatment of HIV/AIDS, certain anti-depressants, stomach acid inhibitors, certain antibiotic and antifungal medications, certain heart medications, and Saint John's Wort.

Dosing Information and Routes of Administration

There is no scientifically defined dose of cannabis for any specific medical condition. If you have not consumed cannabis before, it would be prudent to have someone with you the first time you use it. Dosing remains highly individualized and relies greatly on titration (i.e. finding the right dose where potential therapeutic effects are maximized while adverse effects are minimized). The current available information suggests most individuals use less than 3 grams daily of dried marijuana, whether that amount is taken orally, inhaled, or a combination of both.

Patients with no prior experience with cannabis or cannabinoids are cautioned to begin at a very low dose and to stop therapy if unacceptable or undesirable effects occur.

There are a small number of clinical studies of short duration with smoked/vapourized cannabis for therapeutic purposes. Smoking/vapourizing cannabis results in a more rapid onset of action (within minutes), higher blood levels of cannabinoids, and a shorter duration of acute effects compared to oral ingestion. While there are no established dosing guidelines for smoking/vapourizing cannabis for therapeutic purposes, it is prudent to proceed slowly and cautiously in a gradual fashion, waiting between puffs or inhalations for a minimum of 30 minutes to gauge for strength of effects or for possible overdosing. A dosing increase should be carried out slowly, only if required, and only until you reach a comfortable dose.

In contrast to smoked/vapourized cannabis, there are no clinical studies of cannabis-based edible products for therapeutic purposes (e.g. oils, foods). Absorption of cannabinoids by the oral route is known to be slow and erratic, and the onset of acute effects is delayed with the acute effects generally lasting much longer compared to smoking/vapourizing. Furthermore, dosages for orally administered products are even less well-established than for smoking/vapourization. These particularities have contributed to overdoses with some orally administered products. If ingesting cannabis orally (e.g. in oils, foods) wait a minimum of 2 hours between administration of single doses of oral products to gauge for strength of effects or for possible overdosing.

Stop using cannabis right away and consult your health care practitioner if you begin to experience any side effects (see side effects section for additional information).

Please consult the "Daily amount and dosing information fact sheet" for additional information on dosing.


Symptoms of overdose may include: sleepiness, confusion, disorientation, clumsiness/loss of coordination, fainting, dizziness, chest pain, fast, slow or pounding heartbeat, panic attacks, loss of contact with reality, and seizures.

Seek immediate medical attention in case of overdose, and especially if experiencing chest pain, panic attacks, loss of contact with reality, or seizures.

Cannabis should be used with caution in patients receiving concomitant therapy with other psychoactive drugs because of the potential for greatly enhanced effects on the brain and other parts of the nervous system. An overdose can also occur if a patient is smoking/vapourizing cannabis and at the same time consuming orally administered cannabinoids whether from prescription cannabinoid medications, or from consumption of oils, teas, baked goods or other products.

Side Effects and What To Do About Them

The information on side effects associated with therapeutic use of cannabis is limited. Some of the more well-known side effects are intoxication-like reactions including:

  • dizziness, drowsiness, feeling faint or lightheaded, fatigue, headache;
  • impaired memory and disturbances in attention, concentration and ability to think and make decisions;
  • disorientation, confusion, feeling drunk, feeling abnormal or having abnormal thoughts, feeling "too high", feelings of unreality, feeling an extreme slowing of time;
  • suspiciousness, nervousness, episodes of anxiety resembling a panic attack, paranoia (loss of contact with reality), hallucinations (seeing or hearing things that do not exist);
  • impairments in motor skills and perception, altered bodily perceptions, loss of full control of bodily movements, falls;
  • dry mouth, throat irritation, coughing;
  • worsening of seizures;
  • hypersensitivity reactions (contact dermatitis/hives);
  • higher or lower blood levels of certain medications;
  • nausea, vomiting; and
  • fast heartbeat.

Long term use may

  • increase the risk of triggering or aggravating psychiatric and/or mood disorders (schizophrenia, psychosis, anxiety, depression, bipolar disorder);
  • increase the risk of developing respiratory infections or chronic cough (when smoking);
  • decrease sperm count, concentration and motility, and increase abnormal sperm morphology;
  • negatively impact  the behavioural and cognitive development of children born to mothers who used cannabis during pregnancy;
  • negatively affect cognitive functions (ability to think and make decisions);
  • lead to a decrease in one or more of the effects of cannabis (tolerance);
  • lead to withdrawal-type symptoms when use is abruptly halted or discontinued. Withdrawal symptoms may include anger or aggression, irritability, anxiety, nightmares/strange dreams, insomnia/sleep difficulties, craving, headache, restlessness, and decreased appetite or weight loss, depressed mood, chills, stomach pain, shakiness and sweating; and
  • result in psychological dependence (addiction) which is characterized by impaired control over drug use, compulsive use, continued use despite harm, and craving.

This is not a complete list of side effects. If you experience any side effects or any unexpected effects while using cannabis for medical purposes, stop consuming cannabis immediately and contact a health care practitioner or the emergency department of your nearest hospital.

How the product is supplied

Dried marijuana plant material, fresh marijuana plant material and products derived from fresh or dried marijuana.

How to store the product

Dried marijuana plant material and cannabis products should be stored  in a cool place, preferably away from light and air. See manufacturer's instructions on the product label for recommended storage conditions.

Keep any cannabis and cannabis products out of the reach of children and locked in a safe place to prevent theft, misuse and accidental ingestion by children. This product should not be shared with anyone else.

Reporting Suspected Side Effects

You can report any suspected adverse reactions associated with the use of this product to the Canada Vigilance Program by one of the following 3 ways:

  1. Report online
  2. Call toll-free at 1-866-234-2345
  3. Complete a Canada Vigilance Reporting Form and:
    • Fax toll-free to 1-866-678-6789, or
    • Mail to:
      Canada Vigilance Program
      Health Canada
      Postal Locator 0701D
      Ottawa, Ontario K1A 0K9

Postage paid labels, Canada Vigilance Reporting Form and the adverse reaction reporting guidelines are available on the MedEffect™ Canada Web site.

NOTE: Should you require information related to the management of side effects, contact your health care practitioner. The Canada Vigilance Program does not provide medical advice.

More Information

This document plus the full information prepared for health professionals (the "Information for Health Care Professionals: Cannabis (marihuana, marijuana) and the Cannabinoids") as well as information on dosing can be found on the Health Canada website.

This leaflet was prepared by Health Canada.

Date of latest version July 2016