Cannabis

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What is it?

Cannabis is an herbal drug that is made from the Cannabis plant. It contains chemicals called cannabinoids. Cannabinoids affect the central nervous system, which includes the brain and nerves. Cannabinoids are found in the highest levels in the leaves and flowers of cannabis. These are the parts of the herb that are used to make medicine. Don’t confuse cannabis with hemp. Hemp is a similar plant, but it is grown for the rough parts of the plant (the fiber) as well as for the seeds. Hemp contains very low levels of delta-9-tetrahydrocannabinol (THC), less than 0.3%. Both hemp and cannabis also contain other cannabinoids that are sometimes used as medicine. See specific topics for information on cannabidiol (CBD), cannabidivarin (CBDV), cannabigerol (CBG), and tetrahydrocannabivarin (THCV).

Some people take cannabis extract by mouth or as a spray to be applied under the tongue for pain and symptoms of multiple sclerosis.

Some people inhale cannabis for nausea, vomiting, an eye disease called glaucoma, and many other conditions, but there is no good scientific evidence to support these uses.

Some people also use cannabis to feel good. In this case it is used as a ‘recreational drug’ and is either taken by mouth or smoked (inhaled).

In the U.S., cannabis is illegal under federal law. It is classified as a Schedule I controlled substance. But some states including California, Colorado, Washington, Oregon, Arizona, and others have legalized or decriminalized the use of cannabis. Some countries such as Canada have legalized cannabis use as well.

It is effective?
Natural Medicines rates effectiveness based on scientific evidence according to the following scale: Effective, Likely Effective, Possibly Effective, Possibly Ineffective, Likely Ineffective, Ineffective, and Insufficient Evidence to Rate.

Possibly Effective for …

  • Multiple sclerosis (MS). Spraying a cannabis extract (Sativex, GW Pharmaceuticals) under the tongue seems to improve symptoms of multiple sclerosis such as muscle spasms, the need to urinate, and nerve pain in some people with MS. In the UK, this product is approved as a prescription drug to treat muscle spasms in people with MS. In Canada, this product is approved to treat nerve pain in people with MS. This product is not available as a prescription medicine in the US. Some early research suggests that taking a specific cannabis extract (Cannador, Society for Clinical Research) by mouth helps to reduce muscle stiffness and spasms in people with MS. But other cannabis extracts don’t seem to help to reduce spasms or tremors or help with walking. Some early research shows that smoking cannabis may reduce muscle spasms, pain in the arms and legs, and tremors in people with MS.
  • Nerve pain. Most research shows that smoking cannabis can moderately reduce nerve pain caused by HIV and other conditions. The pain relief lasts for about 2 hours.

Insufficient Evidence to Make a Determination for …

  • Lou Gehrig’s disease (amyotrophic lateral sclerosis or ALS). Early research shows that people with ALS who use cannabis might have improvements in some symptoms, including depression, appetite, spasms, and drooling.
  • Involuntary weight loss in people who are very ill (cachexia or wasting syndrome). Early research shows that taking cannabis extract by mouth does not improve appetite in people with cancer.
  • Nausea and vomiting caused by cancer drug treatment. Early research shows that using a mouth spray containing cannabis helps prevent delayed nausea and vomiting in people treated with cancer drugs. Delayed nausea and vomiting starts at least 24 hours after receiving cancer drugs. Cannabis doesn’t seem to prevent acute nausea and vomiting. This type starts within 24 hours of being treated with cancer drugs.
  • Crohn Disease. Smoking cannabis might reduce symptoms of Crohn disease. But it doesn’t seem to help people become symptom free.
  • Dementia. Limited research suggests that ingredients in cannabis may reduce aggression and agitation in people with dementia.
  • Fibromyalgia. Early research shows that inhaling vaporized cannabis one time might reduce pain in people with fibromyalgia.
  • A group of eye disorders that can lead to vision loss (glaucoma). Cannabis seems to reduce pressure inside the eye in people with glaucoma. But this effect lasts for only 3-4 hours. And cannabis might decrease blood flow to the nerve that sends information from the eye to the brain. This might make vision worse. It’s unclear if cannabis improves sight in people with glaucoma.
  • Involuntary weight loss in people with HIV/AIDS. A survey of people with HIV and loss of appetite found that those who smoke or eat cannabis report having an increased appetite.
  • Migraine. Early research suggests that smoking cannabis might make migraine headaches less painful. But people might also develop tolerance to cannabis, making it less effective over time.
  • Parkinson disease. Early research suggests that smoking cannabis improves symptoms of Parkinson disease such as pain, stiffness, and shakiness within 30 minutes of smoking.
  • Rheumatoid arthritis (RA). Some research suggests that using a mouth spray containing cannabis extract can decrease morning pain and improve sleep in people with RA. But it doesn’t seem to improve joint stiffness in the morning or overall pain severity.
  • A type of inflammatory bowel disease (ulcerative colitis). Early research suggests that some people with ulcerative colitis who smoke cannabis might have a lower risk for serious complications. But it’s unclear whether this is a coincidence.
  • Asthma.
  • Dandruff.
  • Hemorrhoids.
  • Leprosy.
  • Obesity.
  • Preventing organ rejection after kidney transplants.
  • Schizophrenia.
  • Bladder infections.
  • Other conditions.

More evidence is needed to rate cannabis for these uses.

How does it work?
Cannabis contains chemicals that work by binding to specific sites in the brain and on the nerves.

Is there concern for the safety of its use?
When taken by mouth: Cannabis is POSSIBLY UNSAFE when taken by mouth in large amounts or for a long time. Cannabis containing large amounts of THC (50 mg or more) has been linked with anxiety, psychosis, heart attack, and irregular heart rhythm. Regularly taking large amounts of cannabis over a long period of time might cause a disorder called cannabinoid hyperemesis syndrome, or CHS. CHS leads to severe, repeated bouts of nausea and vomiting that don’t respond to typical anti-nausea medicine. In a few reports, CHS has been linked to severe complications that caused death.

Using cannabis for at least 1-2 weeks can also lead to dependence. People with cannabis dependence might experience withdrawal after stopping cannabis use. Symptoms of withdrawal include nervousness, shaking, trouble sleeping, decreased appetite, sweating, headache, and depressed mood. There isn’t enough information to know if cannabis is safe to use in moderation for short periods of time.

When sprayed into the mouth: A specific cannabis extract spray (Sativex, GW Pharmaceuticals) is POSSIBLY SAFE when applied under the tongue. Side effects may include headache, dizziness, drowsiness, dry mouth, nausea, and paranoid thinking. This cannabis extract spray is available as a prescription-only product in the U.K. and Canada. It has not been approved as a prescription product in the U.S.

When inhaled: Cannabis is POSSIBLY UNSAFE when inhaled. Smoking or vaping cannabis can cause various breathing problems such as wheezing and coughing. Some reports suggest that smoking cannabis might cause air-filled cavities in the lungs. These air-filled cavities can cause symptoms such as chest pressure, soreness, and difficulty breathing. Use of e-cigarettes and other vaping products containing THC has been linked to serious lung injury in some people. Smoking cannabis can also cause headache, dizziness, drowsiness, dry mouth, nausea, and paranoid thinking. Smoking cannabis might also increase appetite, increase heart rate, change blood pressure, and impair mental functioning. Some reports suggest that smoking cannabis may also increase the risk of heart problems such as heart attack and abnormal heart rhythm. Regularly smoking large amounts of cannabis for a long time may cause CHS. It might also lead to dependence. People with cannabis dependence might experience withdrawal after stopping cannabis use. Symptoms of withdrawal include nervousness, shaking, trouble sleeping, decreased appetite, sweating, headache, and depressed mood.

Special Precautions & Warnings:

Pregnancy: Cannabis is UNSAFE when taken by mouth or smoked during pregnancy. Cannabis passes through the placenta and can slow the growth of the fetus and increase the risk for premature birth. Cannabis use during pregnancy is also associated with stillbirth, childhood leukemia, abnormalities in the fetus, and the need for intensive care after birth. Cannabis use during pregnancy has also been linked with lower intelligence and increased emotional problems in children when they grow up. Also, cannabis use is associated with an increased risk for anemia and high blood pressure in the mother.

Breast-feeding: Using cannabis, either by mouth or by inhalation is LIKELY UNSAFE during breast-feeding. The chemicals in cannabis pass into breast milk. Too much of these chemicals might slow down the development of the baby.

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 a having heart attack. However, in many cases, people who experienced these events after smoking cannabis had other risk factors for heart-related events such as smoking cigarettes or being overweight.

A weakened immune system: Certain chemicals in cannabis can weaken the immune system. This might make it more difficult for the body to fight infections.

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: Cannabis use, especially frequent use, might increase the chance of getting depression. It can also worsen symptoms of depression and increase thoughts about suicide in those that 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.

Liver disease: It is unclear if cannabis worsens chronic liver disease. While some weak evidence suggests that there might be a link, other evidence has not found a link. Until more is known, be cautious using cannabis.

Multiple sclerosis: Taking cannabis by mouth might make symptoms of multiple sclerosis worse.

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

Schizophrenia: Using cannabis might make symptoms of schizophrenia worse.

Quitting smoking: Using cannabis might make it harder to quit smoking. Early research suggests that people who use cannabis and want to quit smoking cigarettes are less likely to quit smoking after 6 months than people who don’t use cannabis.

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

Surgery: Cannabis affects the central nervous system or the brain and nerves. 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.

Are there any drug interactions?

Disulfiram (Antabuse)

Interaction Rating=Moderate Be cautious with this combination.

Disulfiram (Antabuse) might interact with marijuana. Taking marijuana along with Disulfiram can cause agitation, trouble sleeping, and irritability.

Fluoxetine (Prozac)

Interaction Rating=Moderate Be cautious with this combination.

Taking marijuana with fluoxetine (Prozac) might cause you to feel irritated, nervous, jittery, and excited. Doctors call this hypomania.

Sedative medications (Barbiturates)

Interaction Rating=Major Do not take this combination.

Marijuana might cause sleepiness and drowsiness. Medications that cause sleepiness are called sedatives. Taking marijuana along with sedative medications might cause too much sleepiness.

Sedative medications (CNS depressants)

Interaction Rating=Major Do not take this combination.

Marijuana might cause sleepiness and drowsiness. Medications that cause sleepiness are called sedatives. Taking marijuana along with sedative medications might cause too much sleepiness.

Some sedative medications include clonazepam (Klonopin), lorazepam (Ativan), phenobarbital (Donnatal), zolpidem (Ambien), and others.

Theophylline

Interaction Rating=Major Do not take this combination.

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

Warfarin (Coumadin)

Interaction Rating=Minor Be watchful with this combination.

Using marijuana might increase the effects of warfarin (Coumadin). Smoking marijuana while taking warfarin (Coumadin) might increase the chance of bruising and bleeding.

Are there any interactions with herbs and supplements?
Herbs and supplements that cause sleepiness: Cannabis might cause sleepiness. Using it along with other herbs and supplements that have the same effect might cause too much sleepiness. Some of these supplements include 5-HTP, calamus, California poppy, catnip, hops, Jamaican dogwood, kava, St. John’s wort, skullcap, valerian, yerba mansa, and others.
Herbs and supplements that might slow blood clotting: Using cannabis with other herbs that can slow blood clotting might increase the risk of bleeding in some people. These other herbs include angelica, clove, danshen, ginger, ginkgo, red clover, turmeric, vitamin E, willow, and others.

Are there any interactions with food?
Alcohol: Using dronabinol with alcohol might increase the effects of alcohol on the central nervous system.

What dose is used?
The following doses have been studied in scientific research:

BY MOUTH:

  • For multiple sclerosis (MS): One to five capsules containing cannabis extract standardized to contain 2.5 mg of tetrahydrocannabinol and 0.8-1.8 mg of cannabinol (Cannador, Society for Clinical Research) has been taken twice daily for 12 weeks.

AS A MOUTH SPRAY:

  • For multiple sclerosis (MS): A specific cannabis extract product (Sativex, GW Pharmaceuticals), standardized to contain 27 mg/mL of tetrahydrocannabinol (THC) and 25 mg/mL of cannabidiol (CBD), has been used daily for up to 2 years.

SMOKED OR USED IN A VAPORIZER (INHALED):

  • Nerve pain: Inhaling cannabis that contains tetrahydrocannabinol has been used at least once per day and up to three times per day for up to 2 weeks.

By what other names is the product known?
Anashca, Banji, Bhang, Blunt, Bud, Cannabis, Cannabis sativa, Charas, Dope, Esrar, Gaga, Ganga, Grass, Haschisch, Hash, Hashish, Herbe, Huo Ma Ren, Joint, Kif, Marie-Jeanne, Mariguana, Marihuana, Marijuana, Marijuana Médicale, Mary Jane, Medical Marijuana, Pot, Sawi, Sinsemilla, Weed.

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