Overview

What is medical cannabis?

Cannabis (marijuana) is a drug that is made up of the leaves, flowers, and buds of the cannabis plant. Medical cannabis can help treat symptoms like pain, nausea, and lack of appetite. It may be used by people who have conditions like cancer, AIDS, or multiple sclerosis.

The two active chemicals in cannabis are THC and CBD. THC affects how you think, act, and feel. It can make you feel very happy or "high." CBD can help you feel relaxed without the "high." And it may lessen pain and other symptoms.

There are many types, or strains, of cannabis. Each strain has specific THC-to-CBD ratios. Because of this, some strains have different kinds of effects than others. For example, if a strain of cannabis has a higher ratio of THC to CBD, it's more likely to affect your judgment, coordination, and decision making. Your doctor may be able to tell you about the different strains you can try for your health problem and the effects they might have.

Why is medical cannabis used?

Medical cannabis may help relieve symptoms of some health problems. These may include:

• Nausea and vomiting from chemotherapy (chemo) for cancer.
• Low appetite and weight loss for people who have AIDS.
• Muscle stiffness for some multiple sclerosis or spinal cord injury patients.
• Chronic nerve pain or pain at the end of life.

Prescription medicines that contain THC are also available.

• Nabiximols (Sativex) is a combination medicine that can relieve muscle stiffness in people with multiple sclerosis.
• Nabilone (Cesamet) can relieve nausea and vomiting caused by chemo. It may also improve the appetite of people who have AIDS.

If you think you might want to try medical cannabis, talk to your doctor. Or visit Health Canada's website at www.canada.ca/en/health-canada/topics/cannabis-for-medical-purposes.html for more information.

How do you use medical cannabis?

There are many ways people can use medical cannabis. For example, people can:

• Smoke it as a dried plant.
• Brew it into tea.
• Inhale it as a vapour.
• Spray it under the tongue.
• Apply it to the skin.
• Eat it in homemade foods (edibles).

How soon and how long you may feel the effects of cannabis depends on several things, including how it was taken. For example, when cannabis is smoked, the effects can usually be felt within seconds after inhaling. On the other hand, when cannabis is eaten, the effects may not be felt for up to 90 minutes after you eat it. Since the effects aren't felt right away, people may think they need more and use too much. To avoid this, start with small amounts until you know how edibles affect you. Or follow your doctor's instructions on how much to use.

How much cannabis you've used and how long you've been taking it can also affect how your body responds to it. You may feel the effects of cannabis for hours after you use it.

What are the risks?

Cannabis can interact with other medicines. It can be dangerous if you use it with medicines that make you sleepy or control your mood. These include sedatives, anxiety drugs, antidepressants, and opioids. And it can be dangerous to use cannabis with alcohol, tobacco, and illegal drugs.

Cannabis raises your chance of bleeding if you're on blood thinners. And it can affect your blood pressure. So use caution if you take blood pressure medicine.

Talk to your doctor about other medicines you use before you try cannabis. And talk to your doctor about any personal or family history of substance use disorders or mental health problems. Using cannabis may make these problems worse.

Cannabis may affect your judgment, memory, and concentration. And it may affect your coordination and decision-making. Do not drive or operate machinery after you use cannabis. Talk with your doctor about when it's safe to drive.

Long-term use of cannabis may increase your risk for severe nausea and vomiting. This is called cannabinoid hyperemesis syndrome, or CHS. People who have CHS may feel very thirsty. They may have belly pain and diarrhea. They may vomit more than 20 times a day. Bouts of vomiting may last more than 24 hours.

Some people who use cannabis may develop cannabis use disorder. This can range from mild to severe. People who have it may find it hard to control their use. And they may keep using cannabis even though it's having harmful effects on their life.

The risk of this disorder is higher in people who:

• Start using cannabis when they're young.
• Use it every day.
• Have other substance use disorders and mental health problems.

People who use cannabis often and then quit may have withdrawal symptoms. Symptoms include anxiety, trouble sleeping, and intense cravings for the drug.

If you smoke cannabis, the smoke could damage your lungs. It may make you cough or wheeze. And it may cause lung infections like bronchitis.

If you use medical cannabis and are pregnant (or think you might be) or you are breastfeeding, talk to your doctor. It can affect your baby's development.

As with all medicines, if you use cannabis, store it in a safe and secure place. This is especially important with edible cannabis, which can be easily mistaken for treats or snacks. Make sure that children, friends, family, and pets can't get to them.

What are the side effects?

Cannabis may cause a dry mouth, red eyes, and a faster heart rate. It may make you feel dizzy, drowsy, or anxious, or have paranoid thoughts. And it may make you feel sick to your stomach or vomit.

How can you lower your risk when using cannabis?

• To have the lowest risk, don't use cannabis. But if you do use it, limit your use to 1 day a week at most. ^{footnote 1}
• Know what you're using. Choose products that have low levels of THC. The type (or strain), strength, and effects of cannabis can vary greatly. And understand how soon you may feel the effects of the product you use and how long those effects may last. The product label may have this information.
• Don't drive or operate machinery after using cannabis. Using cannabis may affect your judgment, coordination, and decision making.
• Don't smoke cannabis. The smoke can damage your lungs. If you do smoke it, don't breathe in deeply and don't hold your breath. ^{footnote 1}
• Don't use cannabis with alcohol, tobacco, or illegal drugs.
• Reduce the risk of medicine interactions. Cannabis can be dangerous if you take it with blood thinners or with medicines that make you sleepy, control your mood, or lower your blood pressure. Talk to your doctor about other medicines you use before you try cannabis.
• Keep others safe. Store cannabis in a safe and secure place. This is even more important with edible cannabis, which can be easily mistaken for treats or snacks. Make sure that children, friends, family, and pets can't get to it. And protect others from second-hand smoke.

What is synthetic cannabis?

Synthetic cannabis is made of dried plant material that is treated with chemicals that produce effects like cannabis's effects. It is sold in the form of incense under many names, such as K2 or Spice. The labels often claim that these products are "safe" or "natural." But in fact, the active chemicals are created in a lab. And they have not been tested for safety.

Some people try these products because they are easy to buy and they may not be detected by drug tests.

People think that using these drugs will make them feel the same as when they use cannabis. But these drugs can be stronger than cannabis. And the effects are hard to predict. That's because the type and strength of the chemicals used are often unknown. Some people have reported severe symptoms, such as:

• Fast heart rate and high blood pressure.
• Vomiting.
• Feeling agitated or confused.
• Feeling like others want to harm them (paranoia), or seeing or hearing things that aren't there (hallucinations).