Abstract
Poor adherence to antihypertensive drug therapy is a well-recognized problem and can be assessed by mass spectrometry-based analyses of body fluids. However, contrary statements exist whether drug quantification in blood or qualitative screening in urine is more suitable. The present pilot study aimed to further elucidate the power of blood plasma drug concentrations for adherence monitoring by developing and validating a quantification procedure for nine antihypertensive drugs (amlodipine, bisoprolol, candesartan, canrenone, carvedilol, metoprolol, olmesartan, torasemide, and valsartan) in blood plasma using liquid–liquid extraction and an ultra-high-performance liquid chromatography-ion trap mass spectrometry analysis. The procedure should then be used for an adherence assessment and compared with the results of an established qualitative urine screening. Selectivity, carryover, matrix effect, accuracy, precision, dilution integrity, and stability were successfully validated, except for amlodipine. The applicability was demonstrated by analyzing 19 plasma samples containing 28 antihypertensive drugs and comparing the measured concentrations with calculated dose-dependent reference plasma concentration ranges. The interpretation of plasma concentrations was found to be more sophisticated and time-consuming than that of urine screening results, and adherence could not be assessed in two cases (10%) due to measured plasma concentrations below the lower limit of quantification. However, 14 out of 19 subjects were classified as adherent (75%) and three as nonadherent (15%), in contrast to 19 (100%) that were claimed to be adherent based on the results of the qualitative urine screening. Nevertheless, further data is needed to estimate whether plasma quantification is superior in terms of assessing adherence to antihypertensive medication.
Highlights
They directly and objectively assess patients’ adherence. Such methods are of increasing importance due to the high specificity and sensitivity of, liquid chromatography (LC) coupled to low-resolution or high-resolution mass spectrometry (HRMS) [6,9,15,16,17]
Nine antihypertensive drugs with different chemical properties were chosen for the current pilot study, including the beta-blockers bisoprolol, carvedilol, and metoprolol; the diuretics canrenone and torasemide; the angiotensin receptor blockers (ARBs) candesartan, olmesartan, and valsar
Washing runs are recommended if patient samples containing plasma concentrations above those of Cal 6 were analyzed
Summary
The assessment of patients’ adherence to antihypertensive medication is becoming an increasingly recognized component of successful hypertension management [5]. These measures include interviews, diaries, or questionnaires that are accessible, fast, and inexpensive but were shown to overestimate the adherence [13,14]. Bioanalytical methods, which may be considered as the gold standard [6], allow the unambiguous detection of drugs and/or their metabolites in body fluids and, a proof an intake. They directly and objectively assess patients’ adherence. Repeated measurements were found to improve the adherence [18]
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