Compliance measure development and assessment of theophylline therapy in ambulatory patients.

The objectives of this study were: (a) to develop a drug serum level-based compliance measure which incorporated pharmacokinetic analysis of patient and drug parameters and to compare it to refill records, an indirect measure, and (b) to use that measure to determine whether pharmacist consultation increased compliance. Sixty adult, male chronic obstructive pulmonary disease out-patients who received theophylline were randomly assigned to one of two groups with counselling provided to experimental-group patients only. Compliance was measured by the ratio of actual serum theophylline level to that predicted by pharmacokinetic estimation and by the number of refills in 155 days. More experimental-group patients had actual levels within both +/- 10% and +/- 20% of predicted levels (P = 0.0006 and 0.04). They also obtained more refills than control patients (P = 0.05). The pharmacokinetically based serum level measure appeared to be the more useful measure for identifying non-compliance, which suggests that it is of greater value than existing measures. In addition, the results suggest that comprehensive consultation by a clinical pharmacists can improve compliance with theophylline therapy in the out-patient setting.