Lyrica just keeps on giving. Pfizer's (NYSE: PFE) pain-fibromyalgia-epilepsy drug racked up more than $3 billion in sales last year, and the pharma giant is out for more.

Pfizer announced yesterday that the drug had passed a clinical trial in neuropathic pain after a spinal cord injury. No data were released, but just passing the trial by reducing pain versus placebo should be enough to get the drug an additional indication.

The fact that Lyrica works for neuropathic pain shouldn't come as much of a surprise. The drug is already approved to treat nerve pain associated with diabetes and pain in patients with shingles. Given the related indications, it's probably used off-label by some doctors already.

Still, getting positive results for pain medication can be, quite frankly, a pain. The only way to measure the success is through patients' reporting how they feel, which is very sensitive to the placebo effect. When the data are released, don't be surprised to see 20% or more of the patients saying they felt better after taking the placebo.

Assuming the FDA approves it, Pfizer will be able to market Lyrica for neuropathic pain, something its sales force can't do for off-label use. The added indication may not move Lyrica's needle all that much, but every extra dollar helps, especially as Pfizer loses Lipitor exclusivity this year.

Pfizer better get moving turning the positive data into a supplementary New Drug Application. Bristol-Myers Squibb (NYSE: BMY) and Allergan (NYSE: AGN) are coming up from behind with their pain drug AGN-209323.

Not to be outdone, Pfizer has licensed a compound, ADL5747, from Adolor; data from a phase 2a trial should be available later this year. Preparing now seems prudent; 2018, the year Lyrica goes off patent in the U.S., isn't that far off.

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Fool contributor Brian Orelli holds no position in any company mentioned. Click here to see his holdings and a short bio. Motley Fool newsletter services have recommended buying shares of Pfizer. Try any of our Foolish newsletter services free for 30 days. We Fools may not all hold the same opinions, but we all believe that considering a diverse range of insights makes us better investors. The Motley Fool has a disclosure policy.