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FORT LAUDERDALE, Fla. – Lower-dose submicron particle diclofenac offered good pain control compared with placebo, making it a promising therapeutic option for acute pain, researchers reported here.

Two different doses of diclofenac in the investigational formulation, taken three times a day, were more effective than placebo in reducing pain intensity (P=0.010 for 18 mg and P<0.001 for 35 mg) at 48 hours, reported Charles Argoff, MD, of the Comprehensive Pain Center at Albany Medical College in N.Y., and colleagues at the American Academy of Pain Medicine meeting.

Nonsteroidal anti-inflammatory drug (NSAIDs) are commonly used to treat acute pain, but have the potential for serious, dose-related gastrointestinal, cardiovascular, and renal adverse events, the group explained.

"Investigational submicron particle NSAIDs using proprietary SoluMatrix technology could provide effective pain relief at lower doses than currently available oral NSAIDs," they wrote. Argoff noted that current preparations of diclofenac range from 50 mg to 100 mg twice a day.

The experimental drug's developer, Iroko Pharmaceuticals, presented results from a at the 2012 American Headache Society meeting.

In the current multicenter, double-blind, multiple-dose study, 428 adult patients who'd undergone bunionectomy under regional anesthesia were enrolled. Patients experiencing pain intensity of ≥40 mm on a visual analog scale (VAS) received diclofenac submicron particle capsules (18 or 35 mg thrice daily) or celecoxib (Celebrex, 400 mg loading dose, 200 mg twice daily), or placebo. Hydrocodone-acetaminophen tablets were used as rescue medication for breakthrough pain.

The primary endpoint was VAS summed pain intensity over 48 hours (VAS PID-48).

The authors reported that some pain relief was apparent with diclofenac submicron particle 35 mg (mean VAS PID 4.52) as early as 30 minutes after administration, compared with celecoxib (0.80), diclofenac submicron particle 18 mg (0.31), and placebo (0.12).

At 4 hours after dose administration, diclofenac submicron particle 35 mg provided better pain control versus placebo (P=0.025).

The VAS PID-48 score was 393 for those taking the 18-mg dose of diclofenac, 524 for those taking the 35-mg dose, and 80 for those on placebo.

The most frequent treatment-emergent adverse events with the study drug were postprocedural edema, nausea, headache, and dizziness.

"Because of the particle size and properties, less milligrams of medicine could be required to achieve equal, or better outcome, from the pain reduction point of view with a better side effect profile," Argoff told 番茄社区.

"This is a promising study, but where this drug will fit in to treatment regimen requires further elaboration," Argoff said.

Eduardo Fraifeld, MD, of South Side Pain Solutions in Danville, Va., said he would be like to know how this formulation compares with regular diclofenac in terms of efficacy against pain.

"This is interesting technology but we need more information before we can embrace this," said Fraifeld, who is past president of the American Academy of Pain Medicine.

"The first question this study poses is whether I can get a lower dose of a drug into my patients with lower incidence of adverse events," he said. "The second question would be can my patients afford it? Because even though these drugs may be marginally better, they are certainly going to be more expensive."

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