A new study comparing puffing marijuana to using a pill with the drug found the pills offer longer-lasting pain relief.

According to the nonprofit group ProCon.org, medical marijuana is now legal in 18 states and the District of Columbia. The pill used in the study is Dronabinol. This pill has been FDA-approved since 1985 to treat the nausea, vomiting and loss of appetite that commonly afflict patients with cancer and HIV/AIDS. It is not currently FDA-approved in the U.S. for pain relief.

The small government-sponsored study was the first to compare inhaling versus pill form of medical marijuana use. Researchers at the Substance Use Research Center of the New York State Psychiatric used a sample of 30 healthy, pain-free men and women who were regular smokers of the drug.

The participants were asked to take a pill and then take a puff of marijuana about 45 minutes later. Instead of Dronabinol, some participants were given a placebo pill. The researchers then compared how long each participant could hold their hands in an ice water bath without feeling pain.

Researchers found that either smoking the drug or taking the pill were both effective at pain relief. Participants said the marijuana cigarette took less time to dull pain but wore off quickly. It also caused the participant to feel high much longer than the pill. In contrast, the pill took longer to take effect but pain relief lasted about three to four hours.

"If you think about it, if you're someone who's dealing with chronic pain, you're going to have to be smoking several times a day, and for a lot of people that would not be feasible," wrote study author Ziva Cooper, an assistant professor of clinical neurobiology at Columbia University in New York City.

Each pill or cigarette had a low dosage and participant use was strictly controlled, according to the U.S. National Institute on Drug Abuse, which sponsored the study.