PATIENT NONCOMPLIANCE WITH DRUG REGIMENS - MEASUREMENT, CLINICAL CORRELATES, ECONOMIC-IMPACT

Poor compliance with rationally prescribed drug regimens attenuates be nefits of treatment, making compliance a key link between process and outcome in ambulatory care. Compliance is defined as 'the extent of co rrespondence between the patient's actual dosing history and the presc ribed regimen'. Electronic monitoring methods reveal that >30% of pati ents omit many prescribed doses, irrespective of disease, prognosis, o r symptoms. Some drugs are better able than others to maintain therape utic action during the more common lapses in dosing. These are called 'forgiving' drugs; their duration of action is more than twice the pre scribed interval between doses, allowing action to continue when one o r more doses are missed. Forgiveness has limits, so long lapses in dos ing will nullify action of any drug, with economic consequences that d epend on the clinical consequences of lapsed action, or, with some dru gs, rebound effects. These practical points have only come to light wi th the use of electronic monitoring of compliance, which avoids the bi ases created by tablet counts and other methods that make it easy for patients to censor evidence for omitted doses. All else being equal, t he most forgiving drug in its class will be associated with the best o utcomes, for it will be least impacted by prevalent poor and partial c ompliance.