Ketamine, a drug that is used as an anesthetic, may be a way to safely treat pain, PTSD, depression, and ringing ears (tinnitus), a new study suggests. Since the drug is already approved by the Food and Drug Administration, it could potentially be available sooner and cost less. “It’s a lot more economical to repurpose drugs than to take a new drug and make it from scratch,” says David E. Potter, professor and chair of pharmaceutical sciences at Texas A&M University’s Rangel College of Pharmacy. “Not only in terms of dollars, but also in terms of time.” And because a...