Plasma Trough Concentrations of Antihypertensive Drugs for the Assessment of Treatment Adherence: A Meta-Analysis

'Under pressure': The role of therapeutic drug monitoring in the treatment of hypertension

Antihypertensive drugs do not qualify as optimal candidates for therapeutic drug monitoring (TDM), given their obvious physiological effect, the absence of a clear relationship between drug concentrations and pharmacodynamic outcomes and their wide therapeutic range. However, since non-adherence is a major challenge in hypertension management, using drug concentrations can be of value to identify non-adherence as a first step towards better blood pressure control. In this article we discuss the key challenges associated with measuring and interpreting antihypertensive drug concentrations that are important when TDM is used to improve non-adherence. Additionally, we elaborate on the role of TDM in optimizing antihypertensive drug treatment besides addressing non-adherence by highlighting its value in specific patient groups with altered pharmacokinetic parameters such as female vs. male or elderly patients.

Antihypertensive drug concentration measurement combined with personalized feedback in resistant hypertension: a randomized controlled trial

BACKGROUND

Adherence to antihypertensive drugs (AHDs) is crucial for controlling blood pressure (BP). We aimed to determine the effectiveness of measuring AHD concentrations using a dried blood spot (DBS) sampling method to identify nonadherence, combined with personalized feedback, in reducing resistant hypertension.

METHODS

We conducted a multicenter, randomized, controlled trial (RHYME-RCT, ICTRP NTR6914) in patients with established resistant hypertension. Patients were randomized to receive either an intervention with standard of care (SoC) or SoC alone. SoC consisted of BP measurement and DBS sampling at baseline, 3 months (t3), 6 months (t6), and 12 months (t12); AHD concentrations were measured but not reported in this arm. In the intervention arm, results on AHD concentrations were discussed during a personalized feedback conversation at baseline and t3. Study endpoints included the proportion of patients with RH and AHD adherence at t12.

RESULTS

Forty-nine patients were randomized to receive the intervention+SoC, and 51 were randomized to receive SoC alone. The proportion of adherent patients improved from 70.0 to 92.5% in the intervention+SoC arm ( P  = 0.008, n  = 40) and remained the same in the SoC arm (71.4%, n  = 42). The difference in adherence between the arms was statistically significant ( P  = 0.014). The prevalence of resistant hypertension decreased to 75.0% in the intervention+SoC arm ( P  < 0.001, n  = 40) and 59.5% in the SoC arm ( P  < 0.001, n  = 42) at t12; the difference between the arms was statistically nonsignificant ( P  = 0.14).

CONCLUSION

Personalized feedback conversations based on DBS-derived AHD concentrations improved AHD adherence but did not reduce the prevalence of RH.

Thiazides Attenuate Insulin Secretion Through Inhibition of Mitochondrial Carbonic Anhydrase 5b in β -Islet Cells in Mice

SIGNIFICANCE STATEMENT

Thiazide diuretics (thiazides) are among the most widely prescribed drugs worldwide, but their use is associated with glucose intolerance and new-onset diabetes mellitus. The molecular mechanisms remain elusive. Our study reveals that thiazides attenuate insulin secretion through inhibition of the mitochondrial carbonic anhydrase isoform 5b (CA5b) in pancreatic β cells. We furthermore discovered that pancreatic β cells express only one functional carbonic anhydrase isoform, CA5b, which is critical in replenishing oxaloacetate in the mitochondrial tricarboxylic acid (TCA) cycle (anaplerosis). These findings explain the mechanism for thiazide-induced glucose intolerance and reveal a fundamental role of CA5b in TCA cycle anaplerosis and insulin secretion in β cells.

BACKGROUND

Thiazide diuretics are associated with glucose intolerance and new-onset diabetes mellitus. Previous studies demonstrated that thiazides attenuate insulin secretion, but the molecular mechanisms remain elusive. We hypothesized that thiazides attenuate insulin secretion via one of the known molecular thiazide targets in β cells.

METHODS

We performed static insulin secretion experiments with islets of wild-type, Sodium/chloride co-transporter (NCC) (SLC12A3), and sodium-driven chloride/bicarbonate exchanger (NDCBE) (SLC4A8) knock-out (KO) mice and with murine Min6 cells with individual knockdown of carbonic anhydrase (CA) isoforms to identify the molecular target of thiazides in β cells. CA isoform 5b (CA5b) KO mice were then used to assess the role of the putative thiazide target CA5b in β -cell function and in mediating thiazide sensitivity in vitro and in vivo .

RESULTS

Thiazides inhibited glucose- and sulfonylurea-stimulated insulin secretion in islets and Min6 cells at pharmacologically relevant concentrations. Inhibition of insulin secretion by thiazides was CO 2 /HCO 3- -dependent, not additive to unselective CA inhibition with acetazolamide, and independent of extracellular potassium. By contrast, insulin secretion was unaltered in islets of mice lacking the known molecular thiazide targets NCC or NDCBE. CA expression profiling with subsequent knockdown of individual CA isoforms suggested mitochondrial CA5b as a molecular target. In support of these findings, thiazides significantly attenuated Krebs cycle anaplerosis through reduction of mitochondrial oxaloacetate synthesis. CA5b KO mice were resistant to thiazide-induced glucose intolerance, and thiazides did not alter insulin secretion in CA5b KO islets.

CONCLUSIONS

Thiazides attenuate insulin secretion via inhibition of the mitochondrial CA5b isoform in β cells of mice.

Development and Validation of a Dried Blood Spot Assay Using UHPLC-MS/MS to Identify and Quantify 12 Antihypertensive Drugs and 4 Active Metabolites: Clinical Needs and Analytical Limitations

PURPOSE

As nonadherence to antihypertensive drugs (AHDs) can increase the risk of cardiovascular events, hospitalization, and higher costs, there is a need for a reliable, objective, and easy method to assess nonadherence in patients. The dried blood spot (DBS) sampling method used to measure drug concentrations meets these requirements. For detecting nonadherence, identification is more important than quantification. Owing to their use in clinical practice, it is important to measure multiple AHDs with a single method. Therefore, we developed and validated a single DBS method for 17 commonly used AHDs and 4 active metabolites using ultrahigh performance liquid chromatography-tandem mass spectrometry (UHPLC-MS/MS).

METHODS

Analytical validation of the DBS assay was performed in accordance with the guidelines on bioanalytical method validation of the European Medicines Agency and US Food and Drug Administration as well as the International Association of Therapeutic Drug Monitoring and Clinical Toxicology guidelines.

RESULTS

We validated 12 of the 17 AHDs according to the European Medicines Agency and Food and Drug Administration requirements for bioanalytical method validation. Eleven AHDs were validated for both identification and quantification of drug concentrations, whereas nifedipine was only validated for identification. However, 5 of the 17 AHDs were excluded due to suboptimal validation results. Lercanidipine was excluded due to nonlinearity, and all 4 AHDs measured in the negative mode of UHPLC-MS/MS were not in accordance with one or more of the acceptance criteria and were therefore excluded.

CONCLUSIONS

The described method accurately measured AHDs in DBS and can be used to determine nonadherence in patients. However, method validation revealed a challenging balance between analytical limitations and clinical needs when analyzing multiple drugs using the same method.

Nonadherence in Hypertension: How to Develop and Implement Chemical Adherence Testing

Nonadherence to antihypertensive medication is common, especially in those with apparent treatment-resistant hypertension (true treatment-resistant hypertension requires exclusion of nonadherence), and its routine detection is supported by clinical guidelines. Chemical adherence testing is a reliable and valid method to detect adherence, yet methods are unstandardized and are not ubiquitous. This article describes the principles of chemical adherence testing for hypertensive patients and provides a set of recommendations for centers wishing to develop the test. We recommend testing should be done in either of two instances: (1) in those who have resistant hypertension or (2) in those on 2 antihypertensives who have a less than 10 mm Hg drop in systolic blood pressure on addition of the second antihypertensive medication. Furthermore, we recommend that verbal consent is secured before undertaking the test, and the results should be discussed with the patient. Based on medications prescribed in United Kingdom, European Union, and United States, we list top 20 to 24 drugs that cover >95% of hypertension prescriptions which may be included in the testing panel. Information required to identify these medications on mass spectrometry platforms is likewise provided. We discuss issues related to ethics, sample collection, transport, stability, urine versus blood samples, qualitative versus quantitative testing, pharmacokinetics, instrumentation, validation, quality assurance, and gaps in knowledge. We consider how to best present, interpret, and discuss chemical adherence test results with the patient. In summary, this guidance should help clinicians and their laboratories in the development of chemical adherence testing of prescribed antihypertensive drugs.