Introduced decades ago as the next step in antidepression pills, monoamine oxidase inhibitors (MAOIs) soon fell out of favor. Extremely effective in some people, they caused potentially lethal blood pressure spikes in others because of interactions with food in the gut. That and the subsequent rise of selective serotonin reuptake inhibitors (SSRIs) put them on a shelf. But a new skin patch has resurrected the drugs from obscurity.