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FORT LAUDERDALE, Fla. -- Treatment with extended-release hydrocodone without acetaminophen offered effective relief from chronic low back pain compared with placebo, researchers said here.

After 12 weeks of treatment, about 70% of patients on single-entity hydrocodone bitartrate extended-release capsules (Zohydro ER) reported a reduction in pain by at least 30%, compared with 30% of the patients in the placebo group (P<0.05), reported Richard Rauck, MD, from Wake Forest University in Winston-Salem, N.C., and colleagues at the American Academy of Pain Medicine meeting.

Rauck also told 番茄社区 that about 55% of patients on single-entity extended-release hydrocodone achieved at least a 50% reduction in pain intensity compared with about 20% of patients taking placebo (P<0.05), and that overall, the reduction in pain intensity was about 52% compared with placebo (P=0.008).

Hydrocodone is currently only available in the U.S. in an immediate-release formulation in combination with non-opioid analgesics such as acetaminophen, he noted. Zohydro ER's developer, Zogenix, filed a New Drug Application with the FDA in May 2012.

"For all the drugs we have in this country, we do not have an approved single-entity hydrocodone, which is odd given the fact that hydrocodone is far and away the most prescribed pain reliever," Rauck said.

Rauck's group enrolled 501 patients with moderate to severe chronic low back pain, half of whom were men. More than 75% were Caucasian. All had previous treatment experience with opioids.

They began the study with an open-label conversion/titration phase (≤6 weeks), which was followed by a placebo-controlled, randomized, double-blind treatment phase (12 weeks).

The 501 patients converted from their current opioid to single-entity extended-release hydrocodone that was titrated to a stabilized dose of 20-100 mg twice daily. During the treatment phase, patients (151 per group) received either the study drug or placebo. Rescue medication was allowed.

The primary efficacy endpoint was mean change in average pain intensity from baseline to day 85.

The group reported that the mean change in average pain intensity score from baseline to day 85 was significantly lower in the single-entity extended-release hydrocodone group versus the placebo group (0.48 versus 0.96, P=0.008).

Also, significantly more patients in the study arm were classified as responders compared with those receiving placebo (68% versus 31%, P<0.001).

The mean total daily rescue medication use during the treatment phase was lower in the single-entity extended-release hydrocodone group versus the placebo group (6 mg versus 7.5 mg).

Finally, patients in the study arm were less likely to discontinue treatment compared with those receiving placebo (P≤0.001). Rauck said that at 30 days, the probability of patients on placebo discontinuing the study was 50%, while the probability of patients on single-entity extended-release hydrocodone discontinuing was 10%.

By the end of the study, 60.9% of patients on placebo had discontinued compared with 17.9% of patients taking single-entity extended-release hydrocodone.

The most common side effect for patients treated with single-entity extended-release hydrocodone was constipation (12.9%), nausea, and somnolence.

"We found that hydrocodone extended release is effective and well tolerated for the treatment of chronic low back pain in this population," the authors concluded.

"This is a product that is going to come to the market, and it is going to be useful," predicted Paul Sloan, MD, from the University of Kentucky in Lexington.

"The main advantage is that it takes acetaminophen out of the product," he told 番茄社区. "Acetaminophen can cause liver damage, especially if you have to take it chronically as these patients do. This single-entity product has been a long time coming so this is good."

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