What is Medical Cannabis?
Cannabis (also called marijuana) is a drug derived from the dried leaves, flowers, and buds of the Cannabis sativa plant. The plant produces hundreds of chemical compounds called cannabinoids, which affect the brain and other parts of the body. While many people use cannabis recreationally, medical cannabis refers to its use specifically to treat symptoms of medical conditions. [citation:8]
In many places, cannabis use—even for medical reasons—is not legal. Using it in a location where it’s not allowed by law could lead to legal problems. [citation:2] In the United States, possession of marijuana is illegal under federal law, though over half of the states have legalized it for medical use. [citation:9]
Active Chemical Components: THC and CBD
Cannabis contains more than 100 active cannabinoids. The two most common and well-studied are THC and CBD, which have distinct effects on the body. [citation:2]
| Cannabinoid | Effects | Psychoactive? |
|---|---|---|
| THC (Tetrahydrocannabinol) |
Reduces nausea, stimulates appetite, affects memory and focus. Causes feelings of euphoria or “high.” | Yes |
| CBD (Cannabidiol) |
Reduces pain and inflammation, decreases anxiety, helps control seizures. Does not cause intoxication. | No |
Different varieties (strains) of cannabis have different THC-to-CBD ratios, which affects their therapeutic effects and psychoactive properties. A strain with higher THC is more likely to impair judgment, coordination, and decision-making. [citation:3]
FDA-Approved Cannabis-Derived Medications
The FDA has not approved the cannabis plant itself as medicine. However, it has approved three prescription medications that contain cannabinoids or synthetic cannabinoids: [citation:1][citation:2]
| Medication | Active Ingredient | Indications | |
|---|---|---|---|
| Marinol (Dronabinol) | Synthetic THC | Chemotherapy-induced nausea and vomiting; appetite loss in HIV/AIDS patients | |
| Cesamet (Nabilone) | Synthetic cannabinoid (similar to THC) | Chemotherapy-induced nausea and vomiting (when other treatments have failed) | |
| Epidiolex (Cannabidiol) | Purified CBD | Seizures associated with Lennox-Gastaut syndrome, Dravet syndrome, or tuberous sclerosis complex |
| Condition/Symptom | Evidence Level | Key Findings |
|---|---|---|
| Chemotherapy-induced nausea and vomiting | Strong evidence | THC effectively reduces nausea in patients receiving chemotherapy; may help when standard treatments fail |
| Chronic pain (neuropathic) | Moderate to strong evidence | May reduce shooting/burning pain from nerve damage in conditions like HIV and diabetes |
| Multiple sclerosis (muscle spasticity) | Moderate evidence | May relieve muscle stiffness, spasms, and urinary frequency |
| HIV/AIDS appetite loss | Moderate evidence | May stimulate appetite and reduce weight loss |
| Epilepsy (rare childhood forms) | Strong evidence (for CBD) | Epidiolex (purified CBD) reduces seizure frequency in Lennox-Gastaut and Dravet syndromes |
| Glaucoma | Limited evidence | May lower eye pressure temporarily (hours), but may also reduce blood flow to optic nerve; other treatments work better |
Note on Cancer Treatment: While some people use cannabis to treat cancer, there are no large studies showing that cannabis helps treat cancer. Some animal studies show promise, but more research is needed. [citation:2]
Forms of Medical Cannabis Administration
Medical cannabis can be taken in several forms, each with different onset times and durations of effect. [citation:3][citation:8]
| Method | Onset | Duration | Considerations |
|---|---|---|---|
| Smoking | Seconds to minutes | Up to 6 hours | Damages lungs; may cause bronchitis, coughing, wheezing |
| Vaporizing (vape pens) | Seconds to minutes | Up to 6 hours | Less harmful than smoking but still lung risks; avoid if you have respiratory conditions |
| Edibles (food, drinks) | 30 minutes to 4 hours | Up to 12+ hours | Delayed onset increases risk of overconsumption; effects last longer |
| Oils/tinctures (sublingual) | 15-30 minutes | 4-6 hours | Dosing more predictable; placed under tongue |
| Topicals (creams, patches) | Minutes to hours | Varies | No psychoactive effects; used for localized pain/inflammation |
Pharmacokinetics: Onset and Duration
How cannabis affects a person depends on several factors including dose, method of administration, frequency of use, and individual metabolism. [citation:8]
- Smoking or vaporizing: Effects felt within seconds to a few minutes; peak within 30 minutes; lasts up to 6 hours with residual effects up to 24 hours
- Edibles (eating or drinking): Effects delayed (30 minutes to 4 hours); peak within 4 hours; can last 8-12 hours or longer with residual effects up to 24 hours
Important safety note for edibles: Because effects are not felt immediately, people may think they need more and accidentally take too much. Start with a low dose (e.g., 2.5 mg THC) and wait at least 2 hours before considering more. [citation:8]
Side Effects
Medical cannabis is generally considered safe, but side effects can occur—especially at higher THC doses. Different cannabis varieties have different THC amounts, which can make dosing difficult. [citation:2]
Common Side Effects: [citation:1][citation:2]
- Drowsiness and fatigue
- Dry mouth and dry/red eyes
- Dizziness and lightheadedness
- Headache
- Coughing and wheezing (if smoked)
Less Common/More Serious Side Effects: [citation:2][citation:4]
- Anxiety, panic, or paranoia
- Hallucinations (seeing or hearing things not present)
- Short-term memory loss and difficulty concentrating
- Rapid or irregular heartbeat
- Changes in blood pressure
- Nausea and vomiting
- Confusion
Cannabinoid Hyperemesis Syndrome (CHS): Long-term, frequent use of cannabis (especially high-THC products) may cause severe, recurring episodes of nausea, vomiting, and abdominal pain. People with CHS may vomit more than 20 times a day, with episodes lasting more than 24 hours. [citation:3][citation:8]
High-Dose CBD Side Effects: Doses of CBD higher than 300 mg per day can cause nausea, vomiting, diarrhea, and liver problems. [citation:2]
Contraindications & Populations Requiring Caution
Using cannabis has higher risks for certain populations: [citation:2][citation:8]
| Population | Risk / Recommendation |
|---|---|
| Pregnancy & Breastfeeding | No amount is safe. May cause low birth weight, premature birth, and affect baby’s brain development. Passes into breast milk, causing drowsiness and poor feeding in infants. |
| Under age 25 | Brain is still developing; long-term use may harm memory, concentration, and intelligence. |
| History of psychosis or schizophrenia | Cannabis use may increase the risk of psychosis and worsen symptoms. |
| Bipolar disorder | May worsen manic symptoms (irritability, restlessness, racing thoughts). |
| Heart disease | Some studies link cannabis use to increased risk of heart attack and stroke. |
| History of substance use disorder | Increased risk of developing cannabis use disorder. |
Cannabis Use Disorder & Dependence
Regular cannabis use can lead to cannabis use disorder, which ranges from mild to severe. Signs include: [citation:8]
- Using more cannabis than planned or for longer than intended
- Unsuccessful attempts to cut down or control use
- Spending significant time obtaining, using, or recovering from cannabis
- Experiencing strong cravings
- Failing to meet obligations at work, school, or home
- Continuing use despite physical, psychological, or relationship problems
- Developing tolerance (needing more to achieve the same effect)
- Experiencing withdrawal symptoms when stopping
Withdrawal Symptoms: People who use cannabis regularly and then quit may experience anxiety, trouble sleeping, irritability, decreased appetite, restlessness, and intense cravings. [citation:3][citation:8]
Drug Interactions
Cannabis can interact with other medications and substances, sometimes dangerously: [citation:1][citation:2]
| Substance/Medication | Interaction Effect |
|---|---|
| Alcohol | Additive CNS depression, increased impairment and risk of accidents |
| CNS depressants (benzodiazepines, opioids, sedatives) | Enhanced sedation, drowsiness, and respiratory depression risk; dangerous combination |
| Blood thinners (e.g., warfarin) | May increase bleeding risk; cannabis can affect how these medications are processed |
| Blood pressure medications | Cannabis can affect blood pressure; use with caution |
| Antidepressants (SSRIs) | May increase risk of mania when combined |
| Seizure medications | Cannabis may affect how these medications work and may cause liver issues |
Surgery Precautions: Do not use cannabis for at least 2 weeks before surgery. Cannabis may cause you to need more anesthetic and may increase the risk of complications such as a very fast heart rate. [citation:2]
Safe Use Guidelines
To reduce risks when using medical cannabis: [citation:8]
- Start low, go slow: Begin with a small amount and low-THC products
- Avoid smoking: Choose non-inhaled forms like oils, capsules, or tinctures to protect lung health
- Don’t drive: Cannabis impairs judgment, coordination, and reaction time—impairment can last more than 24 hours
- Don’t combine with alcohol or other drugs: Increases risk of accidents and adverse effects
- Store safely: Keep locked away, out of reach of children and pets; use child-resistant packaging
- Follow up with your provider: Regular monitoring ensures cannabis is working and not interacting with other medications
Legal Status Overview
United States: Possession of marijuana is illegal under federal law. However, over half of the states have legalized marijuana for medical use. In states where medical marijuana is legal, patients need a written certification from a healthcare provider to obtain it from licensed dispensaries. Qualifying conditions vary by state but commonly include cancer, HIV/AIDS, multiple sclerosis, epilepsy, severe chronic pain, and glaucoma. [citation:9]
Canada: Medical cannabis is regulated under the federal Cannabis Act. A healthcare provider must authorize its use. Patients can then obtain cannabis from federally licensed producers or apply to grow their own. [citation:8]
Note: The FDA has approved three prescription medications derived from cannabis (dronabinol, nabilone, cannabidiol), which are legal at the federal level and can be prescribed by any licensed healthcare provider regardless of state cannabis laws. [citation:1]
Warning: Synthetic Cannabis (K2/Spice)
Synthetic cannabis (sold as K2, Spice, or other names) consists of dried plant material treated with lab-created chemicals intended to mimic cannabis effects. These products are NOT safe or natural. They can be stronger than cannabis with unpredictable effects, and have been associated with severe symptoms including rapid heart rate, high blood pressure, vomiting, agitation, paranoia, and hallucinations. [citation:3][citation:7]
Educational Summary
Medical marijuana refers to the use of Cannabis sativa or its extracts to treat symptoms such as chronic pain, chemotherapy-induced nausea, muscle spasticity, and appetite loss. The plant’s two main active compounds are THC (psychoactive, with therapeutic effects) and CBD (non-psychoactive, with anti-inflammatory and anticonvulsant properties). The FDA has approved three cannabis-derived medications: dronabinol (Marinol), nabilone (Cesamet), and cannabidiol (Epidiolex). While studies support cannabis for certain conditions, it has significant side effects including cognitive impairment, dependence risk, and interactions with other medications. Legality varies by jurisdiction; federally illegal in the US but legal for medical use in many states. Pregnant women, individuals under 25, and those with psychosis history or heart disease should avoid use. Safe use includes starting with low doses, avoiding smoking, never driving after use, and not combining with alcohol.
Note: This information is for pharmaceutical educational and reference purposes only. The cannabis plant itself is not FDA-approved as medicine and remains federally illegal in the US. FDA-approved cannabis-derived medications (Marinol, Cesamet, Epidiolex) are available by prescription. This content does not constitute medical advice. Always consult a healthcare provider before using cannabis for medical purposes.
| Quantity | 3.5g, 7g, 28g, 125g |
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