Cannabis for nausea: the short answer
Two prescription cannabinoids, dronabinol and nabilone, are FDA approved to treat chemotherapy-induced nausea and vomiting (CINV) in patients who did not respond to standard antiemetics. A 2017 review by the National Academies of Sciences, Engineering, and Medicine found conclusive evidence for oral cannabinoids as antiemetics in CINV. Evidence for smoked or vaped cannabis is weaker. Evidence for nausea from other causes, such as migraine, surgery, or pregnancy, is limited.
What the clinical evidence covers
Chemotherapy-induced nausea and vomiting
Dronabinol (Marinol, Syndros) is synthetic THC. Nabilone (Cesamet) is a synthetic THC analog. Both come as capsules or oral liquid. Labels list them for CINV when other drugs fail. Dronabinol dosing starts at 5 mg per square meter of body surface 1 to 3 hours before chemotherapy, then every 2 to 4 hours for 4 to 6 doses per day. Nabilone dosing is 1 mg or 2 mg twice daily.
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Other causes
Small trials test THC and CBD for nausea from HIV, post-operative recovery, and migraine. Sample sizes are small. Results vary. No large trial supports cannabis for nausea in pregnancy. Cannabis use during pregnancy is tied to lower birth weight, and CDC and ACOG advise against it.
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THC, CBD, and terpenes
THC binds CB1 receptors in the brainstem and gut. That action drives the antiemetic effect. CBD shows anti-nausea effects in animal models. Human data is thin. Terpenes such as myrcene, limonene, and linalool appear in cannabis marketing for nausea. No controlled human trial shows a terpene relieves nausea at the doses found in flower or oil.
Routes and onset
- Inhalation (smoke or vapor): onset 1 to 10 minutes, duration 1 to 3 hours.
- Oral (edibles, capsules, tinctures): onset 30 to 120 minutes, duration 4 to 8 hours.
- Sublingual tincture: onset 15 to 45 minutes. Absorption varies by product.
- Topicals: no systemic THC absorption at levels that treat nausea.
Nausea makes swallowing hard. Vapor and sublingual routes skip the stomach. Oral THC passes through the liver first. That step converts THC to 11-hydroxy-THC, which is stronger and lasts longer.
Dose
No standard dose exists for cannabis flower or edibles. Federal law limits research. For edibles, start at 2.5 mg THC or less where state rules require dose labeling. Wait 2 hours before a second dose. Keep a log of product, dose, and time. Dronabinol labels warn about dose escalation and dependence.
Side effects and risks
- Drowsiness, dizziness, dry mouth, euphoria
- Impaired coordination and reaction time for 4 to 8 hours after oral THC
- Fast heart rate and low blood pressure at high doses
- Anxiety or paranoia, more often with high THC and no CBD
- Dependence in roughly 1 in 10 adults who use cannabis, higher with daily use
Do not drive after oral THC. Do not combine cannabis with alcohol, opioids, or benzodiazepines without medical advice.
Cannabinoid hyperemesis syndrome
Heavy daily use over years can cause repeated vomiting and abdominal pain. Hot baths and showers relieve it in the short term. The fix is stopping cannabis. Emergency visits for this syndrome rose in states after legalization. If vomiting starts after months or years of daily use, cannabis may be the cause, not the cure.
Questions for a pharmacist or doctor
- Does my current antiemetic regimen have room for a change?
- Do my other drugs interact with THC or CBD?
- Is dronabinol or nabilone covered by my insurance?
- What is the legal status of medical cannabis in my state?
Legal status
Cannabis is Schedule I under federal law. Dronabinol and nabilone are prescription drugs. State medical programs vary on qualifying conditions. Some states list nausea or CINV as a qualifying condition. Check state rules before a purchase.