Cannabis Pharmacokinetics: How Cannabinoids Move Through the Body
What happens to THC and CBD once they enter your body, route by route.
This article is for information only and is not medical advice. Talk to a doctor before using cannabis for a health condition, and do not stop or change prescribed treatment on your own.
Cannabis pharmacokinetics is weird compared to most drugs. How you consume it changes not just speed but which active chemicals your body makes. Smoking hits fast but is unpredictable dose-to-dose. Edibles are slow, variable, and produce a different metabolite that feels stronger. These aren't marketing points—they're real, measurable differences that matter for safety and drug interactions.
Not Medical Advice
This article summarizes published pharmacokinetic data on cannabinoids. It is educational reference material, not medical advice. Individual responses vary substantially with genetics, tolerance, liver function, other medications, and product formulation. Talk to a qualified clinician before using cannabis medically, especially if you take other prescription drugs. Cannabinoids interact with the cytochrome P450 system and can alter blood levels of many medications Strong evidence[1].
Plain-Language Summary
Pharmacokinetics (PK) is what the body does to a drug: Absorption, Distribution, Metabolism, Excretion (ADME).
For cannabis, the practical takeaways are:
- How you take it changes almost everything. Smoking or vaping delivers THC to the brain within minutes. Eating it takes 1–3 hours and produces different metabolites Strong evidence[1][2].
- Bioavailability is low and variable. Only a fraction of the THC in a joint or gummy actually reaches your bloodstream, and that fraction differs from person to person and use to use Strong evidence[1][3].
- THC is very fat-soluble. It gets stored in body fat and released slowly, which is why urine tests can stay positive for weeks in heavy users Strong evidence[4].
- The liver makes oral THC stronger. Oral THC is converted by the liver into 11-hydroxy-THC (11-OH-THC), which is roughly as psychoactive as THC itself and crosses the blood–brain barrier readily. This is why edibles feel different from smoking Strong evidence[1][5].
- Oral CBD has low absorption. Most swallowed CBD never reaches systemic circulation, and food dramatically changes how much does Strong evidence[6].
What We Know Well: Strong Evidence
Inhalation
Smoked and vaporized THC reach peak plasma concentrations in 3–10 minutes, with subjective effects peaking within 15–30 minutes and largely subsiding within 2–4 hours Strong evidence[1][2]. Bioavailability ranges from about 10% to 35%, depending on depth of inhalation, breath-hold, device, and experience Strong evidence[1][3]. Vaporization delivers roughly similar bioavailability to smoking but avoids combustion byproducts Strong evidence[2].
Oral (Edibles, Capsules, Oils)
Oral THC has a slow, erratic absorption curve. Peak plasma levels typically occur 1–3 hours after ingestion but can be delayed up to 6 hours, and inter-individual variability is large Strong evidence[1][5]. Oral bioavailability is low (~4–20%) due to extensive first-pass metabolism in the liver Strong evidence[1].
Oral dosing produces much higher concentrations of the active metabolite 11-OH-THC than inhalation does. 11-OH-THC is comparably psychoactive to THC and contributes to why edibles are often described as longer-lasting and more sedating Strong evidence[1][5].
CBD Absorption
Oral CBD bioavailability in fasted adults is approximately 6% Strong evidence[6]. A high-fat meal increases CBD exposure roughly 4–5-fold Strong evidence[6][7]. This effect is large enough that FDA labeling for Epidiolex (purified CBD) specifically addresses food interactions Strong evidence[8].
Distribution and Elimination
THC is highly lipophilic and distributes rapidly into fatty tissues. The terminal elimination half-life after a single dose is around 20–30 hours, but with chronic use, THC redistributes from fat stores and the apparent half-life extends to several days Strong evidence[1][4]. THC and its metabolites are excreted mostly in feces (~65%) and urine (~20%) Strong evidence[1].
Drug Interactions
Both THC and CBD are metabolized by cytochrome P450 enzymes (CYP3A4, CYP2C9, CYP2C19). CBD particularly inhibits several CYP enzymes and can raise levels of drugs like clobazam, warfarin, and tacrolimus Strong evidence[8][9]. See Cannabis and Polypharmacy Risks for clinical guidance.
What We Understand Partially: Emerging or Weak Evidence
- Sublingual and oromucosal absorption. Products like nabiximols (Sativex) claim buccal absorption bypassing first-pass metabolism. Studies suggest most of the dose is actually swallowed and absorbed in the small intestine, making real oromucosal contribution modest Weak / limited[10]. See Sublingual Cannabis Pharmacokinetics for detail.
- Topical cannabinoids reaching systemic circulation. Non-transdermal topicals (creams, oils) produce minimal systemic THC or CBD levels. Purpose-built transdermal patches can achieve measurable plasma levels, but published pharmacokinetic data are limited Weak / limited.
- Rectal absorption. Claims of high rectal bioavailability often trace to small studies using THC hemisuccinate (a prodrug) that is not used in most suppository products sold today. Bioavailability of native THC via the rectal route is likely low to moderate Disputed[11].
- Fast-acting edibles. Emulsified beverages and dissolvable powders do reach peak plasma faster than oils, but the magnitude and consistency of improvement varies by product and formulation. Marketing often overstates the effect Weak / limited.
- Pediatric and elderly pharmacokinetics. Most published PK data come from healthy adults aged 18–55. Data in children (outside the Epidiolex program) and adults over 65 are sparse Weak / limited.
What Is Not Supported: Folklore and Debunked Claims
- "Edibles kick in at exactly 45 minutes." No. Onset ranges from 30 minutes to 3+ hours depending on the person, the meal, and the formulation Strong evidence[1][5].
- "Holding smoke in longer gets you higher." Most THC absorption from a puff occurs within the first few seconds. Extended breath-holds mainly increase tar exposure and lightheadedness from reduced oxygen, not absorption Strong evidence[2].
- "Indica vs. sativa predicts whether you'll get a body high." Strain names do not reliably predict cannabinoid ratios or effects. Effects depend on THC dose, CBD ratio, and individual metabolism, not strain names Strong evidence.
- "Mango terpenes boost your high by activating myrcene at a 0.5% threshold." No controlled human pharmacokinetics study supports that terpenes in realistic amounts alter cannabinoid absorption or effects Anecdote.
- "CBD has no drug interactions because it's natural." Demonstrably false. CBD inhibits CYP450 enzymes and has documented interactions with many medications Strong evidence[8][9].
What We Genuinely Don't Know
- Pharmacokinetics of minor cannabinoids. The PK of CBG, CBN, THCV, and CBC in humans are barely characterized. Nearly all published human PK data concern THC, CBD, and their primary metabolites No data.
- How chronic heavy use reshapes distribution and elimination. Long-term tissue accumulation and redistribution of cannabinoids in real-world chronic users is inferred from limited data more than directly measured Weak / limited.
- Entourage effect and cannabinoid–terpene interactions. Whether combinations of cannabinoids and terpenes produce pharmacokinetic interactions that meaningfully alter absorption or metabolism at realistic doses remains unresolved Disputed.
- Genetic dosing guidance. Individual variation in CYP2C9 and CYP3A4 polymorphisms clearly affects THC and CBD metabolism, but clinically actionable dosing based on genotype does not yet exist Weak / limited[9].
Comparison with Standard Pharmaceutical Drugs
Cannabis pharmacokinetics is unusual compared to most oral small-molecule pharmaceuticals in three ways:
- High and variable first-pass metabolism. Oral THC bioavailability (~6%) is closer to that of a poorly-absorbed peptide than a typical small molecule. Dose-to-dose and person-to-person variability is large Strong evidence[1].
- An active metabolite formed disproportionately by one route. 11-OH-THC production is much higher after oral dosing, meaning the route of administration changes not just kinetics but also the pharmacodynamic profile and subjective effects Strong evidence[1][5].
- Deep tissue reservoir. Storage in fat and slow redistribution produce a long tail of detectable (though usually sub-psychoactive) drug levels, complicating drug testing interpretation and post-incident forensic analysis Strong evidence[4].
Pharmaceutical cannabinoids—dronabinol (synthetic THC), nabilone (THC analog), Epidiolex (CBD), and nabiximols (THC:CBD spray)—have characterized and FDA-reviewed PK profiles used for approved dosing. Botanical flower and unregulated edibles do not, and label claims on consumer products should be treated with skepticism Strong evidence.
Risks Tied to Pharmacokinetics
- Overdose from edibles. Because oral onset is slow (1–3 hours or more), users often redose before the first dose reaches peak plasma concentration, leading to acute intoxication. This is a leading cause of cannabis-related emergency department visits in legal markets Strong evidence[12].
- Drug–drug interactions. Especially when CBD is taken at anti-epileptic doses alongside inhibited medications like warfarin or clobazam Strong evidence[8][9].
- Impaired driving windows. Inhaled THC impairs psychomotor performance for roughly 3–6 hours, but blood THC levels do not correlate strongly with impairment, complicating per-se driving-under-the-influence laws Strong evidence[13].
- Prolonged positive drug tests in chronic users due to fat storage and slow redistribution—a PK issue with employment and legal consequences, not a pharmacological one Strong evidence[4].
Sources
- Peer-reviewed Huestis MA. Human cannabinoid pharmacokinetics. Chemistry & Biodiversity. 2007;4(8):1770–1804.
- Peer-reviewed Grotenhermen F. Pharmacokinetics and pharmacodynamics of cannabinoids. Clinical Pharmacokinetics. 2003;42(4):327–360.
- Peer-reviewed Ohlsson A, Lindgren JE, Wahlen A, et al. Plasma delta-9 tetrahydrocannabinol concentrations and clinical effects after oral and intravenous administration and smoking. Clinical Pharmacology & Therapeutics. 1980;28(3):409–416.
- Peer-reviewed Sharma P, Murthy P, Bharath MM. Chemistry, metabolism, and toxicology of cannabis: clinical implications. Iranian Journal of Psychiatry. 2012;7(4):149–156.
- Peer-reviewed Newmeyer MN, Swortwood MJ, Barnes AJ, et al. Free and glucuronide whole blood cannabinoids' pharmacokinetics after controlled smoked, vaporized, and oral cannabis administration. Clinical Chemistry. 2016;62(12):1579–1592.
- Peer-reviewed Millar SA, Stone NL, Yates AS, O'Sullivan SE. A systematic review on the pharmacokinetics of cannabidiol in humans. Frontiers in Pharmacology. 2018;9:1365.
- Peer-reviewed Taylor L, Gidal B, Blakey G, Tayo B, Morrison G. A phase I, randomized, double-blind, placebo-controlled, single ascending dose, multiple dose, and food effect trial of the safety, tolerability and pharmacokinetics of highly purified cannabidiol in healthy subjects. CNS Drugs. 2018;32(11):1053–1067.
- Government U.S. Food and Drug Administration. Epidiolex (cannabidiol) prescribing information. Reference ID: 4302880.
- Peer-reviewed Sachse-Seeboth C, Pfeil J, Sehrt D, et al. Interindividual variation in the pharmacokinetics of Δ9-tetrahydrocannabinol as related to genetic polymorphisms in CYP2C9. Clinical Pharmacology & Therapeutics. 2009;85(3):273–276.
- Peer-reviewed Karschner EL, Darwin WD, Goodwin RS, Wright S, Huestis MA. Plasma cannabinoid pharmacokinetics following controlled oral delta9-tetrahydrocannabinol and oromucosal cannabis extract administration. Clinical Chemistry. 2011;57(1):66–75.
- Peer-reviewed Brenneisen R, Egli A, Elsohly MA, Henn V, Spiess Y. The effect of orally and rectally administered delta 9-tetrahydrocannabinol on spasticity: a pilot study with 2 patients. International Journal of Clinical Pharmacology and Therapeutics. 1996;34(10):446–452.
- Peer-reviewed Monte AA, Shelton SK, Mills E, et al. Acute illness associated with cannabis use, by route of exposure: an observational study. Annals of Internal Medicine. 2019;170(8):531–537.
- Government National Highway Traffic Safety Administration. Marijuana-impaired driving: a report to Congress. DOT HS 812 440. 2017.
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