A drug is a pharmaceutical agent, by any route of administration, for prevention, diagnosis, or treatment. Drugs mentioned in the National Ambulatory Medical Care Survey and National Hospital Ambulatory Medical Care Survey are coded by national drug classification (NDC) code entry name, therapeutic class, generic name, ingredients, composition status, prescription status, and control status. For purposes of the Health Care in America: Trends in Utilization report, a specific drug or class of drugs was considered “mentioned” during a visit if it was recorded at least once on the patient record form.

Data on specific drug use are collected in three NCHS surveys: National Ambulatory Medical Care Survey (NAMCS), National Hospital Ambulatory Medical Care Survey (NHAMCS) and National Health and Nutrition Examination Survey (NHANES).

Data collection in the NAMCS and NHAMCS is from the medical record of the physician office or hospital outpatient department visit, rather than from the patient. Generic and/or brand name drugs are abstracted from the medical record, including prescription and over-the-counter drugs, immunizations, allergy shots, and anesthetics that were prescribed, ordered, supplied, administered, or continued during the visit. Prior to 1995, up to five drugs per visit could be reported on the Patient Record Form; in data years 1995 through 2002 up to six drugs could be reported.