Precise measurement of pharma marketing's impact requires physician presciption (Rx) data. One metric used is the total number of prescriptions (TRx; Total Prescriptions) written by physicians for a particular drug over a specific period of time. This includes prescriptions for refills and renewals, which are scripts patients get when they run out of refills. In contrast, NRx (New Prescriptions) do NOT include refills but DO include renewals.
Pharmaceutical companies purchase physician-level prescribing data from companies such as IMS. These data guide pharma salesforce strategies. For example, drug companies can save money by distributing free samples of a new drug only to the biggest prescribers of products in that same class. Sales reps can also use the data to verify their physician clients have prescribed the drugs as promised during sales calls. That information would cahnge the sales messaging in followup calls.