RSO (Rick Simpson Oil)
A whole-plant cannabis extract popularized by Rick Simpson, typically high-THC and consumed orally as a thick black oil.
RSO is just a solvent-extracted whole-plant cannabis concentrate — usually made with ethanol or naphtha, reduced down to a sticky tar. It's potent, cheap to make, and useful as a high-dose oral THC vehicle. What it isn't: a proven cancer cure. Rick Simpson's protocol claims rest on anecdotes, not controlled trials. Treat RSO as what it actually is — a concentrated edible — not as the medical miracle the folklore around it suggests.
Definition
RSO is a crude, full-spectrum cannabis extract made by soaking cannabis plant material in a solvent, straining, and evaporating the solvent off to leave a viscous, near-black oil. Rick Simpson, a Canadian who promoted the preparation starting in the mid-2000s, originally used naphtha; most modern producers use food-grade ethanol [1][2]. Because the extraction is unrefined — no winterization, no distillation — RSO retains cannabinoids, terpenes, chlorophyll, waxes, and plant lipids, which is why it's dark and bitter.
Chemistry and potency
Most RSO is made from high-THC cultivars and tests between roughly 60% and 90% total cannabinoids, dominated by THC Strong evidence. CBD-dominant versions exist but are less common. A grain-of-rice-sized dose (~0.1 g) can contain 60–90 mg of THC — far above the 5–10 mg threshold most edible guidelines recommend for non-tolerant users [3]. Because it's a crude extract, batch-to-batch variation is significant unless the producer lab-tests.
What it does
Pharmacologically, RSO behaves like any other oral THC concentrate: slow onset (30–120 min), long duration (4–8+ hours), and strong psychoactivity due to first-pass conversion of THC to 11-hydroxy-THC in the liver Strong evidence[4]. It is used in legal and gray markets for sleep, pain, appetite, and as a high-dose vehicle for patients who need lots of THC cheaply — including some cancer patients managing chemotherapy side effects Weak / limited[5].
What it doesn't do
RSO has not been shown in controlled human trials to cure cancer, despite Rick Simpson's widely circulated claims. Preclinical (cell and animal) studies show cannabinoids can affect tumor biology, but this has not translated to demonstrated cures in humans Disputed[5][6]. The U.S. National Cancer Institute and FDA explicitly note that no form of cannabis is approved as a cancer treatment [6]. RSO is also not safer or 'more medicinal' than other concentrates simply because it's whole-plant — that's marketing, not pharmacology.
Used in articles
See also: Cannabis Concentrates, Edibles Dosing, 11-Hydroxy-THC, Ethanol Extraction.
Sources
- Reported Lampen, C. (2019). What is RSO? Inside the cannabis oil with a cult following. Leafly.
- Practitioner Simpson, R. Phoenix Tears: The Rick Simpson Story — official site documenting the original protocol and method.
- Government Colorado Department of Public Health and Environment. Marijuana edibles dosing guidance.
- Peer-reviewed Lemberger, L., Martz, R., Rodda, B., Forney, R., & Rowe, H. (1973). Comparative pharmacology of Δ9-tetrahydrocannabinol and its metabolite, 11-OH-Δ9-tetrahydrocannabinol. Journal of Clinical Investigation, 52(10), 2411–2417.
- Peer-reviewed Velasco, G., Sánchez, C., & Guzmán, M. (2016). Anticancer mechanisms of cannabinoids. Current Oncology, 23(S1), S23–S32.
- Government National Cancer Institute (U.S.). Cannabis and Cannabinoids (PDQ®) — Health Professional Version.
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