is my employer allowed to do this?

My employer said that I can't take antidepressants while working for the company. He said that if the FDA found out that an employee was taking a drug to control a mental illness and working with food products that they could have them and I investigated. He said that I could get time off while on them but, could not work while on them. I don't have the money to take time off so I don't know what to do