​It’s no secret that medical marijuana has become a big business in the United States. Medicinal cannabis sales this year are projected to reach $1.7 billion, according to an “investment-grade report on the business of medical marijuana” released this week.

What that means is that marijuana is hard on the heels of Viagra, another of America’s favorite medications. Viagra, the anti-impotence drug, has sales of $1.9 billion a year. The $1.7 billion figure represents estimated sales of marijuana through dispensaries in states with medical marijuana laws. The Sea Change Strategy LLC report, “The State of the Medical Marijuana Markets 2011,” adds new levels of meaning to the term “Green Rush.” It predicts that the number of states where medical marijuana is sold will double in the next five years. The demand for cannabis in states which already have medical marijuana will also grow, according to the report.

About 24.8 million Americans are eligible to get doctor’s recommendations and buy pot in the 15 medical marijuana states and the District of Columbia, the report said. About 730,000 people have already actually done so.