Off-Label Use & Medication Errors

Off-Label Use & Medication Errors

1. Definitions & overview

• Off-label use = prescribing a marketed drug for an indication, patient population, dose, or route that is not listed in the regulator-approved product labeling (the FDA-approved package insert / Summary of Product Characteristics) (Tisdale 3e Ch.1, pp.11). It is legal for a licensed prescriber, but the use is not backed by the regulator's efficacy/safety review for that purpose.
  • Distinguish from unlicensed use (drug not approved at all, e.g. an extemporaneous formulation or an imported drug) — off-label means the drug is approved but the specific use is not.
  • Off-label is a property of how a drug is used, captured in G&G's framework as one of the "factors affecting safe use of medications" alongside prescribing errors, patient genetics and special populations — i.e. it sits with the use of the drug, not the drug (G&G 14e Ch.8, p.146, Fig. 8–1).
• Medication error = "any preventable event that may cause or lead to inappropriate medication use or patient harm while the medication is in the control of the healthcare professional, patient, or consumer" (NCC MERP definition, quoted in Tisdale 3e Ch.3, p.41).
  • Key qualifier: preventable. This separates a medication error from an idiosyncratic/unpredictable ADR — an error implies a defect in the medication-use system, not in the patient's biology (Tisdale 3e Ch.3, p.41–44).
  • Errors are commonly manifested as: administration of the wrong drug, drug overdose, overlooking a documented allergy, or failure to detect a drug–drug interaction (DDI) — each of which can directly cause an adverse drug event (Tisdale 3e Ch.3, p.41).
• Adverse drug event (ADE) = "any untoward medical occurrence that may present during treatment with a medicine, but which does not necessarily have a causal relationship with the treatment" (KDT 8e Ch.6, p.92). ADE is the umbrella term; record the event first, assess causality later when pooling data.
• Adverse drug reaction (ADR) = "any noxious change which is suspected to be due to a drug, occurs at doses normally used in man, requires treatment or decrease in dose or indicates caution in future use of the same drug" (KDT 8e Ch.6, p.92). The WHO definition excludes trivial/expected side effects and excludes poisoning/overdose.
• Drug-induced disease = a functional disturbance (an iatrogenic/physician-induced disease) caused by a drug, which can result from anticipated or unanticipated effects, product impurities, or conditions of use including off-label use and medication errors (KDT 8e Ch.6, p.101; Tisdale 3e Ch.1, p.4).
• Conceptual link (why these two are taught together): premarketing trials establish safety/efficacy only for a narrow labeled use in a narrow population; once marketed, the drug is given off-label and via an error-prone medication-use chain to millions of patients never studied — so the "critical experiment" on safety happens after marketing (G&G 14e Ch.8, p.147–148).