What are we studying?
How do we know how many days a prescribed opioid analgesic was supposed to be taken by a patient? It seems like a simple problem, but the implications are profound – we may mistake a low dose prescription for a high dose prescription if this number is not accurate. For example, if we just know that 30 tablets were dispensed we may not know if they were meant to be taken once a day for 30 days, or 5 times a day for 6 days. Sometimes opioids are taken “as needed for pain” (pro re nata or prn) and the number of days is not specified. How do pharmacists code days’ supply when the prescription says to take two tablets a day, but an odd number of pills is specified?
In most states, pharmacists calculate by hand the “days’ supply” (the number of days a prescription is intended for), because doctors don’t always write out the number of days. The days’ supply then gets put into a database at the pharmacy along with all the other information on a prescription (prescriber and patient names and addresses, drug dispensed, quantity, dose strength, etc.). These databases are used for research, but we don’t know how consistent the days’ supply calculations are. There is discretion at the pharmacist level and we would like to find out how consistent and accurate interpretations of doctors’ instructions are.