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. 2015 Jul 1:9:893-7.
doi: 10.2147/PPA.S86249. eCollection 2015.

Defining medication adherence in individual patients

Alan Morrison  1 , Melissa E Stauffer  1 , Anna S Kaufman  1
Affiliations

Defining medication adherence in individual patients

Alan Morrison et al. Patient Prefer Adherence. .

Abstract

Background: The classification of patients as adherent or non-adherent to medications is typically based on an arbitrary threshold for the proportion of prescribed doses taken. Here, we define a patient as pharmacokinetically adherent if the serum drug levels resulting from his/her pattern of medication-taking behavior remained within the therapeutic range.

Methods: We used pharmacokinetic modeling to calculate serum drug levels in patients whose patterns of dosing were recorded by a medication event monitoring system. Medication event monitoring system data were from a previously published study of seven psoriasis patients prescribed 40 mg subcutaneous adalimumab at 14-day intervals for 1 year. Daily serum concentrations of adalimumab were calculated and compared with a known therapeutic threshold.

Results: None of the seven patients took adalimumab precisely every 14 days. Three patients who took adalimumab at intervals of 6-26 days could be classified as pharmacokinetically adherent, because their daily adalimumab serum concentration never fell below the therapeutic threshold. The four other patients, who took adalimumab at intervals of 7-93 days, could be classified as pharmacokinetically non-adherent, because their adalimumab serum concentration fell below the therapeutic threshold on 3.5%-71.3% of days.

Conclusion: Patients with varying patterns of adalimumab dosing could be classified as pharmacokinetically adherent or non-adherent according to whether or not their serum drug concentrations remained within the therapeutic range.

Keywords: adalimumab; drug administration schedule; drug therapy/utilization; patient compliance; pharmacokinetic adherence; pharmacokinetics.

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Figures

Figure 1
Figure 1
Serum concentration of adalimumab over time for patients whose serum levels (A) did not and (B) did drop below the therapeutic threshold. Notes: Shown are serum levels of adalimumab for each of the seven patients. The timing of each dose for a patient, not specifically indicated in the figure, occurs immediately before each trough point. The bold dashed lines represent the primary therapeutic threshold (4.9 mg/L). The finer dashed lines are alternative cutoffs of 5.4 and 3.6 mg/L.
See this image and copyright information in PMC

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