(Bloomberg Gadfly) -- Things are about to get awkward formakers of drugs targeting multiple sclerosis.

On Thursday afternoon, House Democrats sent letters toprominent biopharma companies that sell MStreatments including Biogen Inc., Novartis AG, Roche Holding AG,and Sanofi, demanding a variety of information about the large and,according to the letters, often seemingly concerted price hikesthey have taken as part of an "in-depth investigation." As would beexpected, the news sparked a decline in the drugmakers' shares.

The investigation will throw an unwelcome spotlight on thesecompanies' pricing practices and force the release of a lot ofdocuments they'd rather not make public. But this is a pageantwe've seen before. As uncomfortable as it will be for thedrugmakers, it may not result in much lastingdamage.

Behind the investigation? The fact that list prices for some MSdrugs have more than doubled. One more than two-decade-old medicinefrom Biogen has seen its price jump by 889 percent since approval,according to one of the letters.

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Pharmaceutical companies usually respond to this sort ofcriticism by arguing that the rebates they give to pharmacy benefitmanagers and insurers make list prices essentially meaningless. Butthose rebates are negotiated in secret. And price hikes have morethan made up for these discounts despite the advancing age of manyof these medicines and heightened competition -- in come cases,propping up revenue after companies can no longer generate it withvolume growth. It's clear why Congress might have a bone topick.

Lawmakers are seeking a wide variety of information anddocuments on profitability, those aforementioned rebates, pricingstrategy, and sales and distribution practices -- and it won't bepleasant for drugmakers. But beyond the headline hangovers, will ithurt the bottom line? History suggests no.

A previous 18-month Congressional investigation intoGilead Science Inc.'s pricing of its life-saving hepatitis Cmedicines reached the less-than shocking conclusion that thecompany priced its medicines in order to maximize revenue. It ledto negative headlines about Gilead and the release of unflatteringinternal documents on the sometimes bloodless calculus of pricingdrugs. But the company didn't cut its list price.Only competition has managed to put a real crimp in Gilead'ssales, not government action.

This is a different situation, of course. Lawmakers are lookingat a bigger set of companies and both pricing of new medicines andincreases on old ones. There may be more skeletons in a broader setof closets. But absent real evidence of wrongdoing -- remember thatit's perfectly legal for pharmaceutical companies to raise prices adnauseum in the U.S. -- the impact will be limited.

After initially making noise on drug pricing, the Trumpadministration has shown little interest in intervening onthis issue. It's unclear if any serious pricing measures could evenget through a Republican-controlled Congress. Any ammunitiongleaned in this investigation won't likely change that.

There may be some impacts on the margins. As long as thisinvestigation is running, companies may be extra cautious withpricing. But Biogen and other companies are already somewhatlimited in their abiliity to benefit from further hikes. And themost recent medicine to hit the market, Roche's Ocrevus, somewhatpre-empted this investigation by pricing at $65,000, substantiallycheaper than some older options.

The increased scrutiny is by no means good news. But asembarrassing as combing through the pricing past might be, there'slittle threat to these firm's futures.