Subtherapeutic Acetazolamide Doses as a Noninvasive Method for Assessing Medication Adherence

Abstract

Adherence monitoring is a vital component of clinical efficacy trials, as the regularity of medication consumption affects both efficacy and adverse effect profiles. Pill‐counts do not confirm consumption, and invasive plasma assessments can only assist post hoc assessments. We previously reported on the pharmacokinetics of a potential adherence marker to noninvasively monitor dosage consumption during a trial without breaking a blind. We reported that consumption cessation of subtherapeutic 15 mg acetazolamide (ACZ) doses showed a predictable urinary excretion decay that was quantifiable for an extended period. The current study describes the clinical implementation of 15 mg ACZ doses as an adherence marker excipient in distinct cohorts taking ACZ for different “adherence” durations. We confirm that ACZ output did not change (accumulate) during 18–20 days of adherence, and developed and assessed urinary cutoffs as nonadherence indicators. We demonstrate that whereas an absolute concentration cutoff (989 ng/mL) lacked sensitivity, a creatinine normalized equivalent (1,376 ng/mg ACZ) was highly accurate at detecting nonadherence. We also demonstrate that during nonadherent phases of three trials, creatinine‐normalized urinary ACZ elimination was reproducible within and across trials with low variability. Excretion was first order, with a decay half‐life averaging ~ 2.0 days. Further, excretion remained quantifiable for 14 days, providing a long period during which the date of last consumption might be determined. We conclude that inclusion of 15 mg ACZ as a dosage form adherence marker excipient, provides a reliable and sensitive mechanism to confirm medication consumption and detect nonadherence during clinical efficacy trials.

The use of objective adherence measures targeting four placebo microbicide delivery forms in the Quatro Clinical Crossover Study

“…To overcome this, others have recently investigated using sub-therapeutic levels of acetazolamide as an 'adherence marker excipient' to assess medication adherence non-invasively through urinary measurements. 15 This type of approach would also be advantageous for assessing nonadherence in all experimental groups of a clinical trial, that is treated and control groups, without the need to unblind the personnel involved. Therefore, objective measures of adherence that are not drug dosage form-specific and easy to measure are still needed and invaluable for assessing adherence to HIV prevention products.…”

“…However, measuring plasma drug concentrations are costly, invasive and cannot be done in real time because the analysis requires time and specialised laboratories. To overcome this, others have recently investigated using sub‐therapeutic levels of acetazolamide as an ‘adherence marker excipient’ to assess medication adherence non‐invasively through urinary measurements 15 . This type of approach would also be advantageous for assessing non‐adherence in all experimental groups of a clinical trial, that is treated and control groups, without the need to unblind the personnel involved.…”