WASHINGTON - Approval last month in the U.S. House of Representatives of legislation that would prohibit the sale of synthetic marijuana and other drugs known as "bath salts" and "plant food" has been delayed indefinitely in the Senate, American Medical News reports.

The House voted 317-98 on December 8 to ban the synthetic drugs, which can mimic the effects of marijuana, cocaine and methamphetamines; however, the Senate companion bill has been held up by an objection from Sen. Rand Paul (R-KY).

Public health officials and physician groups support the legislation because they maintain there is no known medicinal use for the substances, while use of the products has led to numerous medical emergencies.

The American Assn. of Poison Control Centers reported 5,853 calls to poison centers that were related to bath salt exposure from January to November 2011, a dramatic increase from 303 such calls in 2010. The American Medical Association announced its support of a national ban last June.

"These chemicals, when inhaled or injected, cause effects similar to those caused by cocaine and methamphetamine, including paranoia, hallucinations and suicidal thoughts, which have led to self-mutilation, violent behavior and several deaths," wrote AMA Executive Vice President and CEO James L. Madara, MD, in a September letter to the House supporting legislation banning bath salts.

More than 30 states have enacted laws banning the synthetic drugs, which go by brand names such as K2, Spice, and Vanilla Sky.

Some lawmakers said they oppose the legislation as it is written because of its potentially "chilling effect" on scientific research.

"These drugs need to be controlled, but they need to be controlled in such a way that there is no harm done to the vital scientific and medical research that we count on," said U.S. Rep. Zoe Lofgren (D-CA).