Patient compliance with crucial drug regimens: implications for prostate cancer

Understanding of patient compliance with crucial drug regimens has improved markedly since 1986, based on data from two objective methods for monitoring drug dosing by ambulatory patients. Electronic monitoring records times and dates of drug package use, and chemical markers, incorporated into drug dosage forms, are assayed in plasma. These methods remove the camouflage that masks many poor compliers. In contrast, other methods (returned tablet counts, interviews, questionnaires) allow patients easily to censor evidence for delayed or omitted doses. The new methods show many more and larger errors of omission in both trials and practice than previously believed. One patient in about six is punctually compliant, but a modest majority of patients make errors probably too small to attenuate or otherwise modify the actions of all but the most unforgiving medicines. About a third of patients delay or omit many prescribed doses, thus attenuating or otherwise modifying the actions of all but the most forgiving drugs. One patient in about six takes little medicine, though camouflaged as a good complier. Similar patterns of delayed and omitted does prevail, essentially independent of drug, disease, prognosis, or symptoms. In summary, patients take the prescribed dose at intervals longer than prescribed--often by hours, sometimes by days, occasionally by weeks. The clinical and economic consequences of these lapses in dosing are unique to the treatment situation and the severity of disease and comorbidity. The new methods have not yet been applied to androgen-blocking agents, but if the findings resemble those with, e.g. tamoxifen in breast cancer, it will doubtless trigger some rethinking about failed treatment, trial design, and clinical management.