Clayton Dubilier & Rice’s planned sale of drug-compounding company PharMEDium Healthcare Holdings Inc. for $2.58 billion stands to land the private equity firm a nice return on its investment. It also reflects revived interest in compounding pharmacies, which mix or dilute pharmaceutical agents to create hospital-grade dosage forms that aren’t commercially available. The industry faced regulatory and media scrutiny three years ago when New England Compounding Center Inc.’s steroid injections were linked to a deadly meningitis outbreak. Ultimately, 751 patients were diagnosed with a fungal infection after receiving injections of medications produced by the drug-mixing pharmacy; of that total, 64...