A one-time nasal spray has been approved by the Food and Drug Administration as a standalone treatment for depression. The drug made by Johnson & Johnson under the brand name Spravato passed final approval to treat major depressive disorder in patients who have not responded to at least two oral antidepressants.The company said 21 million adults suffer from major depressive disorder but nearly a third dont respond to antidepressants alone.RELATED STORY | Yes, you actually can be allergic to the coldThe one-time treatment targets glutamate, a neurotransmitter, in the brain. It's related to the drug ketamine, which can cause hallucinations and sedation. Because of the adverse side effects, it has to be administered by a medical professional. It can work as quickly as 24 hours to within 28 days, according to Johnson & Johnson.RELATED STORY | FDA says decongestant in many cold medicines doesn't work. So what does?