They don't exist:
Medical marijuana is now legal in 18 states and the District of Columbia, but health insurance doesn't cover it and patients often scramble to cover the cost. "It's an expensive medication, no doubt about it," says Kris Hermes, a spokesman for Americans for Safe Access, a patient advocacy group. "Patients are struggling to afford it, regardless of whether it's available in their state." Hermes estimates that patients pay $20 to $60 for an eighth of an ounce, enough to make about three joints.
The problem is that marijuana remains classified as a Schedule 1 substance, "meaning it has no medical use and a high potential for abuse" – a classification completely detached from reality, of course:
In October, consumer advocates presented oral arguments before the U.S. Court of Appeals for the D.C. Circuit to remove marijuana from that list. Reclassification would make it easier to conduct research on therapeutic uses for marijuana, say advocates, and ultimately make the drug more accessible to patients. Last year, the Drug Enforcement Administration denied a request to reclassify the drug, following an evaluation by the Department of Health and Human Services.