Objective: (1) To explore patient compliance with prescribed drug regimens in the setting of usual care for outpatients with rheumatoid arthritis (RA), gout, and polymyalgia rheumatica (PMR) by utilizing electronic medication event monitors (MEMS(R)) to register openings of the medication package. (2) To examine the influence of disease, frequency of intake of the drug, and class of drug on compliance. (3) To explore the influence of demographic factors, quality of life measures, coping, health status, and functional ability as potential predictors of patient compliance.

Methods: A total of 127 consenting consecutive patients were enrolled: 81 patients with RA, 33 taking nonsteroidal antiinflammatory drugs (13 diclofenac TID and 20 naproxen BID) and 48 taking disease modifying antirheumatic drugs [25 sulfasalazine (SSZ) BID and 23 methotrexate (MTX) once weekly]; 17 patients with PMR starting with prednisolone QD; and 29 patients with gout starting with colchicine (12, QD) or starting with uric acid lowering agents (17, QD). All patients received first prescriptions and were instructed to take the medication as prescribed. Followup was 6 months (gout 12 mo). All patients were aware of the monitoring capability of the package. At baseline a series of questionnaires was completed. We summarized the dosing histories as "taking compliance" (percentage of total prescribed doses taken), "correct dosing" (percentage of doses taken as prescribed), and "timing compliance" (percentage of doses taken within +/- 25% of prescribed interdose intervals).

Results: A total of 26,685 days (> 73 patient-years) were monitored. Compliance expressed as "taking compliance," mean (95% CI), "correct dosing," mean (95% CI), and "timing compliance," mean (95% CI) are: naproxen: 82% (75-90), 68% (57-80), 48% (34-61); diclofenac: 77% (61-93), 67% (47-87), 39% (21-57); MTX: 107% (98-117), 81% (75-87), 83% (76-90); SSZ: 72% (60-84), 55% (44-67), 25% (18-33); prednisolone: 96% (89-102), 88% (83-92), 82% (74-89); colchicine: 65% (48-81), 44% (26-62), 32% (18-46); and uric acid lowering agents: 84% (76-92), 74% (63-85), 65% (52-79). Missed doses occurred more frequently than taking of extra doses: in RA, on 10% of all monitored days there was no evidence of dosing, while on 3% of all monitored days extra doses were taken. In PMR and gout these data are 10% and 4%, and 15% and 7%, respectively. We observed a decline of compliance over time in all study medication groups. Multiple regression analyses showed that the class of medication (symptom modifying or disease controlling), the dosing frequency, the patient's sex, coping pattern (avoidance, passive reaction pattern, and expression of emotions), and the overall health (total Nottingham Health Profile score) together explained 67% of the variance in taking compliance (adjusted R2) (p = 0.002).

Conclusion: Studying patient compliance with prescribed drug regimens utilizing electronic medication event monitors in RA, gout, and PMR showed that large differences exist in compliance between the various medication groups. Compliance declines over time. A regression model shows that it is possible to relate differences in patient compliance to a number of medication and patient related factors.