The potency of marijuana edibles varies dramatically:
Colorado lawmakers made allowances for serious marijuana users by allowing recreational edibles to contain up to 100 milligrams of the psychoactive component THC, roughly equivalent to smoking three joints filled with a gram each of 15 percent THC cannabis.
At the same time, however, the law seemed to have pot novices in mind when it defined each serving size of edible marijuana to be just 10 milligrams of THC. So if you’re following serving directions on each edible, a 75-milligram-THC Mile High Mint bar weighing 45 grams should be consumed in 6-gram chunks, not all at once. And an 8.5-ounce bottle of one of Dixie’s 75-milligram-THC elixirs (just over half the size of a grande Starbucks coffee) should be divvied up into 7½ servings. Even if you abide by these directions, it’s hard to know exactly how much—or how little—THC you’re getting in each bite or gulp.
In March, a Denver Post investigation found that some edibles had just a fraction of the THC listed on their labels (a package of 100-milligram-THC Dr. J’s Jelly Stones contained 0.2 milligrams of THC), while others were considerably more potent than advertised (a 100-milligram-THC Mile High Mint bar boasted 146 milligrams of THC).
Steven Wishnia’s primer on edibles is also worth a read:
“In a nutshell, eaten cannabis gets metabolized by the liver, so delta-9 THC becomes 11-hydroxy-THC, which passes the blood-brain barrier more rapidly and has more of a psychedelic effect than standard THC,” says Understanding Marijuana author Mitch Earleywine, a professor of psychology at the State University of New York at Albany. “Smoked or vaporized cannabis bypasses the liver and doesn’t create the same 11-hydroxy-THC.”
Smoking marijuana gets THC into the body much faster and at higher concentrations, but it stays there much longer after eating. With smoking, as much as 50 to 60 percent of the THC in a joint can get into the blood plasma, and peak concentrations come in 5 to 10 minutes. It “very quickly crosses the blood-brain barrier,” explains Paul Armentano, deputy director of the National Organization for the Reform of Marijuana Laws. With orally administered cannabis, only 10 to 20 percent of the cannabinoids reach the blood plasma, and they do so 60 to 120 minutes later, says Dr. Mark A. Ware, an associate professor of family health at McGill University in Montreal.