JEFFERSON CITY - A House Republican and physician wants to make Missouri the 15th state to permit medical marijuana.

Rep. Rob Schaaf, R-St. Joseph, who has been a family physician in northwest Missouri since 1985 , is one of 15 co-sponsors of a bill that would adjust laws pertaining to the classification of marijuana as a controlled substance in order to allow its use for medical purposes.

Missouri would follow New Jersey -- which passed similar legislation last week -- and thirteen other states and the District of Columbia in allowing doctors to prescribe medical marijuana to ease patients' chronic pain and nausea.

The active chemical in marijuana, tetrahydrocannabinol, is currently available to patients at a high cost. However, not only is regular cannabis less expensive, but it's been found to be more effective, Schaaf said.

"We owe it to our terminally ill patients to provide the most effective treatment," Schaaf said.

Rep. Kate Meiners, D-Jackson County, is sponsoring the bill, which was read for the second time on Tuesday and has not been assigned to a committee. Last year Meiners' medical marijuana bill was effectively killed by not receiving a committee hearing.

The bill returns this session, however, with more co-sponsors, including Schaaf. In addition to being the bill's only Republican co-sponsor, Schaaf is also a member of the House's health care policy committee.

Since last session, President Barack Obama also widened the door for the bill to pass when he told federal prosecutors not press charges against medical marijuana users if done in a state where it's legal. The federal law maintains cannabis as a Schedule I drug.

Schaaf stressed that the bill would not legalize marijuana overall.

"Most people don't understand the issue," he said.

Schaaf also added that he think the bill won't pass as written.

Last November, the American Medical Association, often cited by the Drug Enforcement Administration, reversed its long-standing policy on marijuana.

According to its report, the association "urges that marijuana's status as a federal Schedule I controlled substance be reviewed with the goal of facilitating the conduct of clinical research and development of cannabinoid-based medicines." However, the association does not endorse medical marijuana programs at the state level.

Opposition is concerned that legalizing medical marijuana will make policing the drug more difficult.

Missouri Department of Public Safety and the office of Attorney General Chris Koster could not be reached for comment.