Junk Magic by Karen Chance

Half werewolf Lia de Croissets is a member of the War Mage Corps, the police branch of the world’s leading magical organization, the Silver Circle. She’s an instructor assigned to train new recruits, a job considered to be significantly tougher than combat—especially right now. There is a war going on in the supernatural world, and the other side has discovered a deadly new tactic.
Popular street drugs have been laced with a potent narcotic known as “fey wine”. An import from Faerie, the wine has been known to bring out latent magical abilities in humans, but this version does much more than that. It is so strong that it is drawing forth dangerous talents that were long ago deliberately weeded out of the magical gene pool.
Someone is making monsters out of regular people and turning them loose on an unsuspecting and very unprepared world. The Corps cannot afford to fight on two fronts at once, so Lia gets a new class: one made up of the only people who might be able to counter these latest threats. It remains to be seen if a group of sullen, disaffected magical outlaws can come together to contain an ancient plague before the whole world gets sick.