It may be malpractice--malpractice is the provision  of medical care, including the prescription of medicine, which is careless or otherwise fails to  meet contemporary standards  of acceptable medical care. Proscribing you an overdose of an anti-depressant could easily be malpractice. If it was malpractice, the doctor could be liable, or financially responsible, for your medical bills, for any lost wages, and if you suffered lasting harm, for pain and suffering.If the out-of-pocket costs (e.g. your share  of medical bills) is a few hundred dollars, it's probably not worth a lawsuit or retaining a lawyer, though you could certainly send a letter to the doctor demanding compensation and informing him or her that you may take legal action if not compensated. If the costs are several thousand dollars, it's probably worth consulting with a medical malpractice attorney to explore your options.