Overview

Cannabis (Cannabis sativa) is an herbal drug. It contains chemicals called cannabinoids, including delta-9-tetrahydrocannabinol (THC) and cannabidiol (CBD).

The cannabinoids in cannabis work by binding to specific sites in the brain and on the nerves. There are over 100 cannabinoids in cannabis, but THC and CBD are the most well-studied. Cannabinoids are found in the highest levels in the leaves and flowers of the plant.

Cannabis is commonly used as a recreational drug. People also commonly use cannabis for multiple sclerosis (MS) and nerve pain. It is also used for nausea, vomiting, migraine, and many other conditions, but there is no good scientific evidence to support these uses. There is also no good evidence to support using cannabis for COVID-19.

Don't confuse cannabis with hemp. Hemp contains very low levels of THC, less than 0.3% according to legal standards. Both hemp and cannabis also contain cannabinoids such as CBD, cannabidivarin (CBDV), cannabigerol (CBG), and others. Unlike hemp, cannabis is illegal under federal law in the US. It is classified as a Schedule I controlled substance. But some states have legalized or decriminalized recreational use.



Uses & Effectiveness

Possibly Effective for

  • Multiple sclerosis (MS). Spraying a cannabis extract spray (Sativex) under the tongue seems to improve symptoms of MS such as muscle spasms and nerve pain. This product is not available in the US. In the UK and Canada, this product is a prescription drug.
  • Nerve pain. Smoking cannabis seems to moderately reduce nerve pain caused by HIV and other conditions. The pain relief lasts for about 2 hours.

There is interest in using cannabis for a number of other purposes, but there isn't enough reliable information to say whether it might be helpful.

Side Effects

When taken by mouth: Cannabis is possibly unsafe when used in large amounts or long-term. Edible cannabis containing 50 mg or more of THC has been linked with serious side effects. Regularly taking large amounts of cannabis might cause cannabinoid hyperemesis syndrome (CHS). CHS leads to severe nausea and vomiting that doesn't respond to typical anti-nausea drugs. Also, using cannabis for at least 1-2 weeks can cause dependence.

When sprayed into the mouth: A specific cannabis extract (Sativex) is possibly safe. This is a prescription-only product in the UK and Canada. It is not approved in the US.

When inhaled: Cannabis is possibly unsafe when used in large amounts or long-term. Smoking or vaping cannabis can cause breathing problems and is linked with increased risk of heart attack and stroke. Vaping products containing THC have been linked to serious lung injury. Regularly smoking cannabis may cause CHS and/or dependence.

Special Precautions and Warnings

When taken by mouth: Cannabis is possibly unsafe when used in large amounts or long-term. Edible cannabis containing 50 mg or more of THC has been linked with serious side effects. Regularly taking large amounts of cannabis might cause cannabinoid hyperemesis syndrome (CHS). CHS leads to severe nausea and vomiting that doesn't respond to typical anti-nausea drugs. Also, using cannabis for at least 1-2 weeks can cause dependence.

When sprayed into the mouth: A specific cannabis extract (Sativex) is possibly safe. This is a prescription-only product in the UK and Canada. It is not approved in the US.

When inhaled: Cannabis is possibly unsafe when used in large amounts or long-term. Smoking or vaping cannabis can cause breathing problems and is linked with increased risk of heart attack and stroke. Vaping products containing THC have been linked to serious lung injury. Regularly smoking cannabis may cause CHS and/or dependence.

Pregnancy: Using cannabis is unsafe during pregnancy. Cannabis passes through the placenta and can slow the growth of the fetus and increase the risk for premature birth, stillbirth, childhood leukemia, abnormalities, or the need for intensive care after birth. It can also lead to lower intelligence and emotional problems in the child when they grow up. It also increases the risk for anemia and high blood pressure while pregnant.

Breast-feeding: Using cannabis is likely unsafe while breast-feeding. The chemicals in cannabis pass into breastmilk and stay in breastmilk for longer than 6 weeks, even after cannabis use has been stopped. These chemicals might slow down or change the development of the baby. Avoid all cannabis use if planning to breastfeed.

Bipolar disorder: Using cannabis might make manic symptoms worse in people with bipolar disorder.

Heart disease: Cannabis might cause fast heartbeat and high blood pressure. It might also increase the risk of having heart attack.

Allergies to fruits and vegetables: Cannabis might increase the risk of an allergic reaction in people with allergies to foods like tomatoes, bananas, and citrus fruit.

Depression: Using cannabis might increase the risk for depression. It can also worsen symptoms of depression and increase thoughts about suicide in those who already have depression.

Diabetes: Cannabis use might make it harder to control blood sugar levels. It might also increase the risk for long-term complications from diabetes. Until more is known, be cautious using cannabis.

Epilepsy: High doses of cannabis might cause seizures in people with epilepsy. There have been several reports where high doses of cannabis have caused seizures.

Weakened immune system: Because cannabis can be contaminated with fungus, there's some concern that using cannabis might put people with weakened immune systems at risk for fungal infections.

Liver disease: It is unclear if cannabis worsens chronic liver disease. Until more is known, be cautious using cannabis.

Lung diseases: Cannabis can make lung problems worse. Regular use might increase the risk of lung cancer. Some people develop a type of lung disease called emphysema.

Irregular heartbeat: Cannabis might increase the risk for dangerous irregular heartbeat in people at high risk for these conditions.

Schizophrenia: Using cannabis might make symptoms of schizophrenia worse.

Quitting smoking: Using cannabis might make it harder to quit smoking.

Stroke: Using cannabis after having a stroke might increase the risk of having a second stroke.

Surgery: Cannabis affects the central nervous system. It might slow the central nervous system too much when combined with anesthesia and other medications during and after surgery. Stop using cannabis at least 2 weeks before a scheduled surgery.

Problem swallowing: Giving cannabis oil to someone with a swallowing problem might increase the risk of the oil entering the lungs.

Interactions

    Moderate Interaction

    Be cautious with this combination

  • Medications changed by the liver (Cytochrome P450 2C19 (CYP2C19) substrates) interacts with Cannabis

    Some medications are changed and broken down by the liver. Cannabis might change how quickly the liver breaks down these medications. This could change the effects and side effects of these medications.

  • Medications changed by the liver (Cytochrome P450 2C9 (CYP2C9) substrates) interacts with Cannabis

    Some medications are changed and broken down by the liver. Cannabis might change how quickly the liver breaks down these medications. This could change the effects and side effects of these medications.

  • Medications that increase the breakdown of other medications by the liver (Cytochrome P450 2C9 (CYP2C9) inducers) interacts with Cannabis

    Cannabis is changed and broken down by the liver. Some drugs increase how quickly the liver changes and breaks down cannabis. This could change the effects and side effects of cannabis.

  • Medications that increase breakdown of other medications by the liver (Cytochrome P450 3A4 (CYP3A4) inducers) interacts with Cannabis

    Cannabis is changed and broken down by the liver. Some drugs increase how quickly the liver changes and breaks down cannabis. This could change the effects and side effects of cannabis.

  • Medications that decrease the breakdown of other medications by the liver (Cytochrome P450 2C9 (CYP2C9) inhibitors) interacts with Cannabis

    Cannabis is changed and broken down by the liver. Some drugs decrease how quickly the liver changes and breaks down cannabis. This could change the effects and side effects of cannabis.

  • Medications that decrease the breakdown of other medications in the liver (Cytochrome P450 3A4 (CYP3A4) inhibitors) interacts with Cannabis

    Cannabis is changed and broken down by the liver. Some drugs decrease how quickly the liver changes and breaks down cannabis. This could change the effects and side effects of cannabis.

  • Sedative medications (Barbiturates) interacts with Cannabis

    Cannabis might cause sleepiness and slowed breathing. Some medications, called sedatives, can also cause sleepiness and slowed breathing. Taking cannabis with sedative medications might cause breathing problems and/or too much sleepiness.

  • Sedative medications (CNS depressants) interacts with Cannabis

    Cannabis might cause sleepiness and slowed breathing. Some medications, called sedatives, can also cause sleepiness and slowed breathing. Taking cannabis with sedative medications might cause breathing problems and/or too much sleepiness.

  • Theophylline interacts with Cannabis

    Taking cannabis might decrease the effects of theophylline. But there isn't enough information to know if this is a big concern.

  • Medications that slow blood clotting (Anticoagulant / Antiplatelet drugs) interacts with Cannabis

    Cannabis might slow blood clotting. Taking cannabis along with medications that also slow blood clotting might increase the risk of bruising and bleeding.

  • Medications changed by the liver (Cytochrome P450 2E1 (CYP2E1) substrates) interacts with Cannabis

    Some medications are changed and broken down by the liver. Cannabis might change how quickly the liver breaks down these medications. This could change the effects and side effects of these medications.

  • Medications changed by the liver (Cytochrome P450 3A4 (CYP3A4) substrates) interacts with Cannabis

    Some medications are changed and broken down by the liver. Cannabis might change how quickly the liver breaks down these medications. This could change the effects and side effects of these medications.

  • Medications moved by pumps in cells (P-glycoprotein Substrates) interacts with Cannabis

    Some medications are moved in and out of cells by pumps. Cannabis might change how these pumps work and change how much medication stays in the body. In some cases, this might change the effects and side effects of a medication.

  • Warfarin (Coumadin) interacts with Cannabis

    Using cannabis might increase the effects of warfarin. Smoking cannabis while taking warfarin might increase the chance of bruising and bleeding.

  • Anesthesia interacts with Cannabis

    Using cannabis might increase how much anesthesia your doctor needs to give to you for surgery. Tell your doctor if you regularly use cannabis. If possible, stop using cannabis at least 2 weeks before surgery.

  • Medications for dissolving blood clots (Thrombolytic drugs) interacts with Cannabis

    Cannabis might slow blood clotting. Taking cannabis with medications used for dissolving blood clots might increase the chance of bleeding and bruising.

  • Alcohol interacts with Cannabis

    Using cannabis with alcohol might increase the effects of alcohol on the central nervous system. This might increase the risk for some side effects, such as drowsiness and mood changes.

    Minor Interaction

    Be watchful with this combination

  • Medications for mental conditions (Antipsychotic drugs) interacts with Cannabis

    Taking cannabis with some medications used for schizophrenia does not seem to reduce how well they work.

Dosing

Cannabis is commonly used in capsules, edible products, sprays, vape products, and cigarettes. Products can vary significantly depending on how much delta-9-tetrahydrocannabinol (THC), cannabidiol (CBD), and other cannabinoids they contain. Speak with a healthcare provider to find out what type of product and dose might be best for a specific condition.

Cannabis is illegal under federal law in the US. It is classified as a Schedule I controlled substance. Some states have legalized or decriminalized use.
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CONDITIONS OF USE AND IMPORTANT INFORMATION: This information is meant to supplement, not replace advice from your doctor or healthcare provider and is not meant to cover all possible uses, precautions, interactions or adverse effects. This information may not fit your specific health circumstances. Never delay or disregard seeking professional medical advice from your doctor or other qualified health care provider because of something you have read on WebMD. You should always speak with your doctor or health care professional before you start, stop, or change any prescribed part of your health care plan or treatment and to determine what course of therapy is right for you.

This copyrighted material is licensed from Therapeutic Research Center, LLC. Information from this source is evidence-based and objective, and without commercial influence. For professional medical information on natural medicines, see Natural Medicines Comprehensive Database Professional Version.
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