There is a category of cannabis medicine that gets discussed far less than it should: the products that went through regulatory approval. Three cannabinoid medicines have cleared drug regulators in one or more countries. Their approval documents are the most reliable information available on what cannabinoids do in humans, because a regulator read the trial data and wrote down exactly which claims survived.
This post sets the three side by side: what each drug is, what it is approved for, what the trials showed (including where they failed) and how a standardised pharmaceutical differs from unstandardised flower or oil. It follows on from the earlier posts on the endocannabinoid system and on THC and CBD. The detailed trial discussions are in separate posts on MS spasticity and on chemotherapy-induced nausea and vomiting. The general evidence base and dosing are covered in topic 1358 and topic 1312.
Active ingredients are named throughout; brand names appear only where necessary to identify the product in the regulatory record.
All doses in this post are copied from the product labels for reference only. They are not dosing guidance.
Nabiximols
What it is. A standardised whole-plant cannabis extract delivered as an oromucosal spray. Each 100-microlitre spray delivers 2.7 mg THC and 2.5 mg CBD, an approximately 1:1 ratio. Unlike the other two drugs on this list, it is plant-derived rather than synthetic, and it retains other plant constituents.
Approved for. Symptom improvement in adults with moderate to severe spasticity due to multiple sclerosis who have not responded adequately to other anti-spasticity medication and who show meaningful improvement during an initial trial of therapy. It is used as an add-on to existing anti-spasticity medication. This is the only indication in the UK Summary of Product Characteristics, and it is now the only indication in Canada.
Where. Approved in the United Kingdom (2010), Canada and a number of European countries. In 2022, Jazz Pharmaceuticals described it as approved in 29 markets outside the US. Not approved in the United States.
What the trials showed. The effect sizes are modest, and they need careful reading. The UK/EU dossier included an enriched-responder design (Novotna et al., 2011). Every participant first took nabiximols single-blind for four weeks. Only those whose spasticity improved by at least 20% (241 patients) were then randomised to stay on it or switch to placebo. Over the 12-week randomised phase, the difference between groups was 0.84 points on a 0–10 spasticity scale. That design measures the effect in people already known to respond, not in everyone with MS spasticity, so it flatters the average effect. A real effect in a population with few options, and not a dramatic one. The full trial discussion is in the post on MS spasticity.
Where it failed. In Canada, nabiximols had also held two conditional approvals (NOC/c): for neuropathic pain in MS (2005) and as an add-on analgesic in advanced cancer pain (2007). Health Canada later removed both, reported in its January 2020 Health Product InfoWatch, because the confirmatory studies “did not support the therapeutic advantage” of the drug for neuropathic and cancer pain. In the United States, Jazz reported in June 2022 that its Phase III RELEASE MSS1 trial in MS spasticity did not meet its primary endpoint (change in lower-limb muscle tone at day 21). Later that year Jazz discontinued the US nabiximols programme.
That is the most useful single fact in this section: a cannabinoid medicine was tested properly for cancer pain, and the regulator withdrew the indication when the confirmatory evidence did not hold up. That result is almost never mentioned in the popular literature about cannabis and pain.
Adverse effects, from the UK label: dizziness and fatigue are the most commonly reported reactions in the first four weeks, with dizziness occurring mainly during initial dose titration. Somnolence and disorientation are also listed.
Dronabinol
What it is. Synthetic delta-9-THC in sesame oil, taken orally as a capsule or oral solution. A single molecule, precisely dosed: no CBD, no terpenes, no other cannabinoids.
Approved for, by the US FDA, two indications:
- Nausea and vomiting associated with cancer chemotherapy in patients who have not responded adequately to conventional antiemetics, approved in 1985. Capsule label dose: 5 mg/m² one to three hours before chemotherapy, then every two to four hours afterwards, for four to six doses a day; maximum 15 mg/m² per dose. Detailed discussion is in the post on chemotherapy-induced nausea and vomiting.
- Anorexia associated with weight loss in patients with AIDS, added in 1992. Capsule label dose: 2.5 mg twice daily, one hour before lunch and dinner, up to a maximum of 10 mg twice daily.
The oral solution is dosed differently from the capsules.
Mechanism. Partial agonist at CB1.
Pharmacokinetics. This is where oral THC differs sharply from inhaled:
| Parameter | Value |
|---|---|
| Oral bioavailability | 10–20% |
| Onset | 0.5–1 hour |
| Half-life | initial ~4 h; terminal 25–36 h |
| Metabolism | CYP2C9 and CYP3A4 |
The low bioavailability and slow onset are the pharmacological explanation for why oral cannabinoids are so easy to overdose by impatience. The long terminal half-life means repeated doses build up over days. The same mechanism lies behind edibles, covered in the earlier post on edibles and decarboxylation.
Adverse effects at ≥3%: abdominal pain, dizziness, euphoria, nausea, paranoid reaction, somnolence, abnormal thinking, vomiting. Additional concerns: neuropsychiatric effects, haemodynamic instability in cardiac patients, seizure risk in susceptible individuals, and abuse potential.
Contraindicated in hypersensitivity to dronabinol or to sesame oil.
Note what the AIDS indication is. It is appetite. Dronabinol has no antiviral activity and does not substitute for antiretroviral therapy. This distinction is discussed further in the post on overclaimed indications.
Nabilone
What it is. A synthetic cannabinoid, structurally similar to THC but not identical. Oral capsule.
Where. Approved in the United States (FDA, 1985) and Canada, and licensed in the United Kingdom, in each case for chemotherapy-induced nausea and vomiting.
Approved for, in wording worth quoting exactly from the US label: “treatment of the nausea and vomiting associated with cancer chemotherapy in patients who have failed to respond adequately to conventional antiemetic treatments.”
That final clause is the whole story of nabilone’s regulatory position. It is a second-line drug. The regulator did not conclude it was better than standard antiemetics; it concluded it had a place for patients whom standard antiemetics had failed. The efficacy discussion is in the post on chemotherapy-induced nausea and vomiting.
Schedule. US DEA Schedule II (high abuse potential), a more restrictive classification than dronabinol capsules carry (Schedule III).
Dose (label). Usually 1–2 mg twice daily, maximum 6 mg daily in divided doses three times a day, with the first dose one to three hours before chemotherapy.
Warnings from the label, and these are unusually strong for an antiemetic:
- Psychiatric effects may persist 48–72 hours after treatment stops. Not hours. Days.
- CNS effects including dizziness, drowsiness, hallucinations and psychosis
- Tachycardia and orthostatic hypotension
- No driving or operating machinery
- Contraindicated with alcohol and other CNS depressants
- Close adult supervision required, particularly during initial use
Why this matters: standardisation
The single largest practical difference between these three drugs and unstandardised cannabis is not potency or purity. It is that you know what you took.
A dronabinol capsule contains 2.5, 5 or 10 mg of THC. Every capsule. Every batch. A nabiximols spray delivers 2.7 mg THC and 2.5 mg CBD. Every spray.
Unstandardised flower or oil varies by cultivar, by batch, by harvest, by storage duration, by how it is prepared, and, for inhaled routes, by inhalation technique. Two grams from the same jar consumed a month apart are not the same dose.
That is why the trial evidence exists for these three products and not for flower. You cannot run a dose-response study on an input you cannot dose. It is also why the approved indications are narrow: a regulator will only approve what a trial demonstrated, and the trials were run on a fixed, reproducible product.
The trade-off runs the other way too, and it is worth stating fairly. Nabiximols is expensive. Dronabinol has slow, variable onset that some patients find unusable for breakthrough symptoms. A single-molecule THC product also produces a different experience from a whole-plant preparation, which is part of why some patients prefer flower even where the pharmaceutical is available.
Standardisation buys you predictability and evidence. It costs money and flexibility. Both halves of that are true.
What is not on this list, and why
Cannabidiol as a pharmaceutical, approved for specific severe epilepsy syndromes, is a fourth approved cannabinoid medicine and needs its own discussion.
Everything else has not been through this process: CBD wellness products, cannabis oils, flower sold for medical use, “full spectrum” extracts. That is not a statement that they do nothing. It is a statement that no regulator has read a trial and written down what they do, which means the claims attached to them are the seller’s claims rather than a regulator’s findings.
The Thai context
We could not confirm that any of these three products is registered with the Thai FDA, so do not assume they are available in Thailand as approved medicines. The Thai framework routes patients differently.
Under the Notification of the Ministry of Public Health Re: Controlled Herbs (Cannabis) B.E. 2568, issued 26 June 2025, cannabis flower is a controlled herb. It may be dispensed only against a prescription on form ภ.ท. 33 (PT 33) from an authorised practitioner, for no more than 30 days per prescription and for single use only (no refills). Flower that is sold must come from a GACP-certified cultivation site. Online sale or advertising of flower is not permitted, and recreational use is not permitted. In 2026, two Ministerial Regulations B.E. 2569 tightened licensing: one for cannabis and hemp extracts (in force 26 April 2026) and one for controlled-herb licences (No. 2, in force 30 April 2026). Neither changes the PT 33 prescription rules. A Cannabis Control Act is still only a draft: the Cabinet approved it on 22 September 2026 and sent it to the House.
Thailand also has standardised products of its own. Since 2019 the Government Pharmaceutical Organization (GPO) has produced cannabis oils in THC-rich, CBD-rich and 1:1 THC:CBD formulas for use in public hospitals. Current formulas and availability should be checked with the treating hospital.
So a Thai patient’s medical cannabis is usually either prescribed flower or a hospital-dispensed extract, not one of the three products above with their registration dossiers. That has a consequence worth stating plainly: the evidence base described in this post does not automatically transfer. The trials were run on nabiximols, dronabinol and nabilone. A prescribed flower preparation, or even a standardised Thai extract, is a different product, and inferring its effects from those trials is an extrapolation, not a citation.
Sources: Sativex Oromucosal Spray, UK Summary of Product Characteristics (MHRA-approved, via electronic medicines compendium), Sativex Oromucosal Spray - Summary of Product Characteristics (SmPC) - (emc) | 602; Sativex Product Monograph, Canada, https://pp.jazzpharma.com/pi/sativex.ca.PM-en.pdf; Health Canada, Health Product InfoWatch, January 2020, https://www.canada.ca/en/health-canada/services/drugs-health-products/medeffect-canada/health-product-infowatch/january-2020.html; Novotna A, et al. Eur J Neurol 2011;18(9):1122–31 (PMID 21362108); Jazz Pharmaceuticals, third-quarter 2022 results (SEC filing), https://www.sec.gov/Archives/edgar/data/1232524/000123252422000045/a3q22financialpr.htm; Marinol (dronabinol) capsules, US prescribing information, DailyMed - MARINOL- dronabinol capsule; Syndros (dronabinol) oral solution, FDA label, NDA 205525; Institute of Medicine, Marijuana and Medicine (1999), ch. “Development of Cannabinoid Drugs”, Checking your browser - reCAPTCHA; Cesamet (nabilone) FDA prescribing information, NDA 018677; Cesamet Product Monograph, Health Canada; Nabilone 1 mg Capsules, UK SmPC, Nabilone 1mg Capsule - Summary of Product Characteristics (SmPC) - (emc) | 12767; GPO cannabis oil supply to public hospitals (2019), https://idpc.net/news/2019/08/thai-health-ministry-receives-cannabis-oil-for-medical-use.