Investor concerns over accounting practices at Valeant Pharmaceuticals International Inc (VRX.TO) have put a spotlight on the little-known and fast-growing specialty pharmacy industry. Shares of Valeant fell 19 percent on Wednesday after influential short-seller Citron Research accused the company of using specialty pharmacies, through a network led by its partner Philidor Rx Services, to inflate its revenue, an allegation the drugmaker denied.