You win some and you lose some. For Pfizer (NYSE:PFE), it happened with the same drug within a week.

First, the bad news: The company's once-daily version of Lyrica failed to show a statistically significant reduction in seizure frequency in patients with epilepsy. It appears the placebo group improved better than expected.

Of patients taking the highest dose, 45.9% experienced a 50% reduction in seizure frequency compared to when they started the trial, but the placebo group saw 35.8% reduction by the same measure. While the higher dose was numerically higher, there's a 9% chance that difference happened by chance alone; the Food and Drug Administration wants the likelihood of a difference happening by chance to be lower than 5%.

The placebo effect didn't disrupt a second trial in patients with fibromyalgia; my guess is that the trial design had a lot to do with it. Rather than looking at improvement versus placebo, Pfizer measured how patients that responded to the drug were affected if they were taken off the drug.

Of the patients who had a response to once-daily Lyrica but were then randomized to receive placebo, 70.7% reported that the drug stopped working. For patients that remained on the drug, 54% reported that the drug stopped working. Patients that took placebo also failed quicker in an average of 22 days compared to 58 days for patients remaining on the drug.

Pfizer is running one more phase 3 trial in patients who have nerve pain caused by shingles. Normally, trials for a controlled-release product are fairly low risk. Lyrica is already approved for all three indications; the only difference for these trials is that the pill is designed to release the drug slowly so it only has to be given once a day. But indications that involve pain are always tricky since there aren't any laboratory tests to measure pain, and companies have to rely on patients to reporting how they feel.

Having a once-daily pill could help Pfizer compete with Eli Lilly's (NYSE:LLY) Cymbalta, which is given once daily for its pain indication (it's sometimes dosed more often for depression, but Lyrica doesn't have that indication). GlaxoSmithKline (NYSE:GSK) and Xenoport (NASDAQ: XNPT) recently gained approval to market Horizant for patients experiencing pain after having shingles, which has to be dosed twice a day. All things being equal, the convenience of once-daily dosing will trump having to take multiple pills a day, especially for chronic conditions.

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