medical prescription medical prescription a prescription, often abbreviated ℞ or rx, is a formal communication from a physician or other registered health-care professional to a pharmacist, authorizing them to dispense a specific prescription drug for a specific patient. historically, it was a physician's instruction to an apothecary listing the materials to be compounded into a treatment—the symbol ℞ (a capital letter r, crossed to indicate abbreviation) comes from the first word of a medieval prescription, latin: recipere ("take thou"), that gave the list of the materials to be compounded. the prescription symbol, ℞, as printed on the blister pack of a prescription drug format and definition ℞medical prescriptionin unicodeu+211e ℞ prescription take (&rx;)related