Pain Therapeutics ( PTIE) shares rose Thursday after the company said its experimental painkiller is less addictive than other similar drugs on the market.

Shares traded at 17 times average volume, closing the regular session up 7 cents, or 1.2%, at $5.94 after the company reported results of the first of phase III clinical trials studying the effectiveness and safety of the drug Oxytrex. Phase III is the last round of trials before a drug is submitted for approval by the Food and Drug Administration.

In the company-sponsored trials, 719 patients with severe chronic low-back pain were given Oxytrex; the commonly prescribed opioid pain medication, oxycodone; or a placebo. Compared with oxycodone, side effects were 20% less in those who received Oxytrex, and withdrawal symptoms were more than 50% less likely, making the drug less addictive. The two drugs were equally effective. The company plans to discuss a new drug application plan with the FDA in late 2005.

Oxycodone, sold by Purdue Pharma under the brand name OxyContin, has been under intense scrutiny in recent years; according to the FDA and the Drug Enforcement Administration, the abuse of OxyContin is associated with serious consequences including addiction, overdose and death.

"Doctors and patients avoid opioid therapy fearing possible addiction," said Dr. Lynn Webster, lead investigator in the Oxytrex trials in a company press release. Webster, a pain management specialist and medical director of Lifetree Clinical Research & Pain Clinic in Salt Lake City, believes that "a new drug that provides pain relief yet curbs dependency stands to gain rapid acceptance in the medical community."