Monitoring Antihypertensive Medication Adherence by Liquid Chromatography-Tandem Mass Spectrometry: Method Establishment and Clinical Application.

ABSTRACT: Proper medication compliance is critical for the integrity of clinical practice, directly related to the success of clinical trials to evaluate both pharmacological-based and device-based therapies. Here, we established a liquid chromatography-tandem mass spectrometry method to accurately detect 55 chemical entities in the human urine sample, which accounting for the most commonly used 172 antihypertensive drugs in China. The established method had good accuracy and intraday and interday precision for all analyses in both bench tests and validated in 21 hospitalized patients. We used this method to monitor and ensure drug compliance and exclude the inferring impacts of medication compliance as a key confounder for our pivotal trial of a catheter-based, renal mapping and selective renal denervation to treat hypertension. It is found that in the urine samples from 92 consecutive subjects, 85 subjects (92.4%) were consistent with their prescriptions after 28 days run-in periods, 90 (97.8%) and 85 (95.5%) patients completely complied with their medications during the 3-month and 6-month follow-up period, respectively. Thus, using the liquid chromatography-tandem mass spectrometry method with specificity, accuracy, and precision, we ensured drug compliance of patients, excluded the key confounder of drug interferences, and ensured the quality of our device-based clinical trial for treatment of hypertension.

Hyphenation of field-amplified sample injection and transient isotachophoresis in CE for the determination of sotalol and metoprolol in human urine samples.

A sensitive approach of capillary electrophoresis coupled with field-amplified sample injection and transient isotachophoresis was developed for the simultaneous determination of two ß-blockers: sotalol and metoprolol. In this dual focusing technique, the samples were prepared via only dissolution in ultrapure water and then injected electrokinetically. Phosphate acted as both the background electrolyte and the leading electrolyte. Its optimized concentration was 80 mM. A total of 25 mM of glycine was used as the terminating electrolyte. Under optimum conditions, good separation of sotalol and metoprolol was achieved within 10 min. In comparison with the conventional method, the sensitivity enhancement factors were up to 1031 and 919 for sotalol and metoprolol, respectively. The proposed method was employed in the determination of sotalol and metoprolol in spiked human urine samples. The limits of detection and limits of quantitation obtained via ultraviolet detection were 5 and 12 ng/mL, respectively, for sotalol, and 10 and 25 ng/mL, respectively, for metoprolol. The intraday repeatability values were lower than 2.7 and 1.7% for peak area and migration time, respectively. The assay is a simple and efficient strategy with potential for application in clinical and biochemical laboratories for monitoring sotalol and metoprolol.

Assessment of adherence to diuretics and ß-blockers by serum drug monitoring in comparison to urine analysis.

Purpose: Toxicological screenings for identifying antihypertensive drugs proved to be a useful tool for assessing adherence. However, misinterpretation may occur in case of highly metabolised drugs with low renal excretion, as well as for drugs with a prolonged detectability. The aim of the present study was to compare a recently developed therapeutic drug monitoring (TDM) method based on serum concentrations to an urine drug detection method for assessing adherence in outpatients.Materials and methods: Corresponding urine and blood samples were obtained at the same time from 26 outpatients without supervised medication. Urine and serum analyses were performed using established high-performance liquid chromatography-tandem mass spectrometry (LC-MS/MS) methodologies. Adherence was assumed if drugs were detectable in urine or if serum concentrations were above individually calculated lower dose-related concentrations (DRC) or literature-based therapeutic reference ranges (TRR) used as cut-off, respectively.Results: The identification of analytes in urine as well as the quantitative serum assay were performed for atenolol (n = 6 patients), bisoprolol (n = 8), nebivolol (n = 6), canrenone (n = 6, metabolite of spironolactone), hydrochlorothiazide (n = 12) and furosemide (n = 2). On the basis of drug detectability in urine, adherence was assumed in 88% of prescriptions. In 81% (DRC) and 50% (TRR) of the serum analyses the cut-off value was exceeded, which confirms patients' adherence in a lower number. Differences in adherence rates were found in five patients, mainly for ß-blockers.Conclusion: This study suggests that assessment of adherence can be performed more precisely on the basis of serum drug concentrations with individually calculated lower DRC than by using the TRR or qualitative urinalysis.

Adherence to antihypertensive drug treatment in patients with apparently treatment-resistant hypertension in the INSPiRED pilot study.

PURPOSE: Drug adherence may be a major problem in the therapy of hypertension and in the diagnosis of therapy resistance. Adherence can be assessed by indirect methods or by direct methods like drug detection in urine with liquid chromatography-mass spectrometric methods. MATERIALS AND METHODS: The current analysis included patients with apparently treatment- resistant hypertension (TRH) referred for renal denervation (RDN) and included in the the INSPiRED pilot trial (NCT01505010). Adherence was repeatedly assessed by toxicological urine analysis over a time range of up to 17 months in a total of 18 patients. RESULTS: In the first urine samples of 18 patients the adherence rate (percentage of number of detected vs. prescribed medical drugs) ranged from 0 to 100% with a median of 73.2%. In further urine samples collected during the following up to 17 months every individual patient exhibited considerable changes in the adherence rate, neither a constancy nor a tendency could be deduced. CONCLUSIONS: Urine analysis results exhibit variation over time and an assessment at a certain time point cannot be regarded as representative or predictor for future behavior. Therefore, it appears necessary to perform drug adherence testing repeatedly over time.

Hollow-fiber-supported liquid membrane microextraction of amlodipine and atorvastatin.

A simple, environmentally friendly, and efficient method, based on hollow-fiber-supported liquid membrane microextraction, followed by high-performance liquid chromatography has been developed for the extraction and determination of amlodipine (AML) and atorvastatin (ATO) in water and urine samples. The AML in two-phase hollow-fiber liquid microextraction is extracted from 24.0 mL of the aqueous sample into an organic phase with microliter volume located inside the pores and lumen of a polypropylene hollow fiber as acceptor phase, but the ATO in three-phase hollow-fiber liquid microextraction is extracted from aqueous donor phase to organic phase and then back-extracted to the aqueous acceptor phase, which can be directly injected into the high-performance liquid chromatograph for analysis. The preconcentration factors in a range of 34-135 were obtained under the optimum conditions. The calibration curves were linear (R(2) ≥ 0.990) in the concentration range of 2.0-200 µg/L for AML and 5.0-200 µg/L for ATO. The limits of detection for AML and ATO were 0.5 and 2.0 µg/L, respectively. Tap water and human urine samples were successfully analyzed for the existence of AML and ATO using the proposed methods.

Population-based meta-analysis of hydrochlorothiazide pharmacokinetics.

Hydrochlorothiazide (HCTZ) is a thiazide diuretic used for the treatment of hypertension and edema associated with fluid overload conditions such as congestive heart failure (CHF). A population-based meta-analysis approach in NONMEM® was used to develop a PK model to characterize the time-course of HCTZ concentrations in plasma and excretion into the urine for healthy subjects and CHF patients. Data from healthy subjects receiving 100 mg of oral HCTZ were supplemented with additional plasma concentration and urinary excretion versus time data published in the literature following administration of oral HCTZ doses ranging from 10 to 500 mg to healthy subjects or patients with renal failure, CHF or hypertension. A two-compartment model with first-order oral absorption, using a Weibull function, and first-order elimination best described HCTZ PK. Creatinine clearance (CLCR ) was a statistically significant predictor of renal clearance (CLR ). Non-renal clearance was estimated to be 2.44 l/h, CLR was 18.3 l/h and T1/2,α was 1.6 h and T1/2,ß was 14.8 h for a typical individual with normal renal function (CLCR = 120 ml/min). However, CLR was reduced to 10.5, 5.47 and 2.70 l/h in mild (CLCR = 80 ml/min), moderate (CLCR = 50 ml/min) and severe (CLCR = 30 ml/min) renal impairment, respectively. Model diagnostics helped to demonstrate that the population PK model reasonably predicts the rate of urinary HCTZ excretion over time using dosing history and estimated CLCR , allowing for the convenient assessment of PK-PD relationships for HCTZ when given alone or in combination with other agents used to treat fluid overload conditions.

Simultaneous determination of aliskiren and hydrochlorothiazide in tablets and spiked human urine by ion-pair liquid chromatography.

An alternative method for analysis of aliskiren (ALI) and hydrochlorothiazde (HCT) in combined dosage forms by ion-pair reversed phase high performance liquid chromatography was developed and validated. The pharmaceutical preparations were analyzed using a C18 column (250 mm x 4.6 mm, 3 microm) with a mobile phase consisting of 25% methanol, 50% sodium monobasic phosphate aqueous solution containing 6 mM tetrabutylammonium bromide and 25% water at pH 7.2. Isocratic analysis was performed at a flow rate of 1 mL/min and a column temperature of 30 degrees C under direct UV detection at 210 nm. Paracetamol was used as internal standard. The validation was performed according to the ICH guidelines. The proposed method was linear over the concentration range of 0.250 to 60 and 0.1 to 10 microg/mL for ALI and HCT, respectively. The limits of detection and quantitation (LOD and LOQ) were 0.075 and 0.198 microg/mL, respectively, for ALI and 0.04 and 0.062 microg/mL, respectively, for HCT. The method proved to be specific, sensitive, precise and accurate with mean recovery values of 101.1 +/- 0.32% and 100.9 +/- 0.41% for ALI and HCT, respectively. The method robustness was evaluated by means of an experimental design. The proposed method was applied successfully to spiked human urine samples with mean recoveries of 98.8 +/- 0.36% and 98.1 +/- 0.21% for ALI and HCT, respectively.

Assessment of the drug-drug interactions between fimasartan and hydrochlorothiazide in healthy volunteers.

AIM: Fimasartan is a selective angiotensin II receptor blocker. Hydrochlorothiazide (HCTZ), which is used to treat hypertension and edematous conditions, is coadministered with many antihypertensive agents. METHODS: An open-label, randomized, multiple-dosing, 2-arm, 1-sequence, 2-period study was conducted to assess the effects of fimasartan (240 mg) on HCTZ (25 mg) or vice versa in 18 and 14 healthy male volunteers, respectively. During each drug administration period, drugs were given once daily for 7 days, with a 7-day washout period between the 2 administration periods. RESULTS: The respective geometric mean ratios of fimasartan for AUC τ,ss and C max,ss with HCTZ were 1.30 [90% confidence interval (CI), 0.84-2.01] and 1.17 (90% CI, 0.93-1.47) compared with fimasartan alone. The respective geometric mean ratios of HCTZ for AUC τ,ss and C max,ss with fimasartan were 0.94 (90% CI, 0.84-1.04) and 0.88 (90% CI, 0.80-0.97) compared with HCTZ alone. Plasma renin activity indicated no significant differences between fimasartan monotherapy and coadministered treatment. CONCLUSIONS: Fimasartan administered alone or in combination with HCTZ was well tolerated at the described dosages. Coadministration of fimasartan increased the urinary excretion of HCTZ and urine volume, but these observations are unlikely to have any clinical relevance.

Spectrofluorimetric determination of aliskiren in dosage forms and urine.

A new, simple and sensitive spectrofluorimetric method has been developed for the determination of aliskiren (ALS) in dosage forms and human urine. The method is based on the reaction between ALS and fluorescamine in borate buffer solution, pH 9, to give a highly fluorescent derivative which is measured at 482 nm after excitation at 382 nm. The factors affecting the reaction were carefully studied. The fluorescence intensity concentration plots were rectilinear over the range 140-1400 ng/mL with a limit of detection 13.47 ng/mL and limit of quantitation 40.81 ng/mL. The developed method was successfully applied to the analysis of the drug in tablets and human urine; the average recoveries (n = 6) were 99.88 ± 0.38% and 99.57 ± 0.44%, respectively. The analytical performance of the method was fully validated and the results were satisfactory. The stability of the drug was studied by subjecting it to acidic, basic, oxidative and thermal degradation.

Development of a HPLC method for the determination of losartan urinary metabolic ratio to be used for the determination of CYP2C9 hydroxylation phenotypes.

BACKGROUND: Losartan is metabolized to losartan carboxylic acid (E-3174) by the polymorphic cytochrome CYP2C9. The aim of the study was to develop a high-performance liquid chromatographic (HPLC) method with fluorescence detection for simultaneously measuring losartan and its metabolite E-3174 in urine to evaluate the losartan urinary metabolic ratio (MR: losartan/E-3174) for CYP2C9 phenotyping in humans. METHODS: The compounds were separated in a reversed-phase chromatographic column and detected by fluorescence at a wavelength of 250 nm for excitation and of 370 nm for emission. RESULTS: No analytical interferences with endogenous compounds were found, and the extraction recoveries were over 88%. Limits of quantification of 2 ng mL-1 for losartan and 5 ng mL-1 for E-3174 were achieved, as well as good reproducibility with coefficients of variation of <9% in all cases. Analyses with the present HPLC method show significant differences (p<0.05) in losartan MRs between the four CYP2C9 genotype groups in 13 Spanish healthy volunteers. CONCLUSIONS: The method developed is simple and affordable, as well as sensitive and reliable to calculate the MR. Therefore, it appears to be useful for CYP2C9 phenotyping using losartan as a drug test in populations, such as Hispanics with different allele combinations.

Measuring adherence to antihypertensive medication using an objective test in older adults attending primary care: cross-sectional study.

Analysis of urine samples using liquid chromatography-tandem mass spectrometry (LC-MS/MS) has previously revealed high rates of non-adherence to antihypertensive medication. It is unclear whether these rates represent those in the general population. This study aimed to investigate whether it is feasible to collect urine samples in a primary care setting and analyse them using LC-MS/MS to detect non-adherence to antihypertensive medication. This study used a prospective, observational cohort design. Consecutive patients were recruited opportunistically from five general practices in UK primary care. They were aged ≥65 years with hypertension and had at least one antihypertensive prescription. Participants were asked to provide a urine sample for analysis of medication adherence. Samples were sent to a laboratory via post and analysed using LC-MS/MS. Predictors of adherence to medication were explored with multivariable logistic regression. Of 349 consecutive patients approached for the study, 214 (61.3%) gave informed consent and 191 (54.7%) provided a valid urine sample for analysis. Participants were aged 76.2 ± 6.6 years and taking a median of 2 antihypertensive medications (IQR 1-3). A total of 27/191 participants (14.2%) reported not taking all of their medications on the day of urine sample collection. However, LC-MS/MS analysis of samples revealed only 4/27 (9/191 in total; 4.7%) were non-adherent to some of their medications. Patients prescribed more antihypertensive medications were less likely to be adherent (OR 0.24, 95%CI 0.09-0.65). Biochemical testing for antihypertensive medication adherence is feasible in routine primary care, although non-adherence to medication is generally low, and therefore widespread testing is not indicated.

Nonadherence to antihypertensive medications amongst patients with uncontrolled hypertension: A retrospective study.

ABSTRACT: Medication nonadherence represents a modifiable risk factor for patients with hypertension. Identification of nonadherent patients could have significant clinical and economic implications in the management of uncontrolled hypertension.We analysed the results of 174 urinary adherence screens from patients referred to Addenbrooke's Hospital, Cambridge, for uncontrolled hypertension. Cases were identified for evaluation by results of liquid chromatography-tandem mass spectrometry of urine samples (males: 91; females: 83; age range: 17-87). We performed a binary logistic regression analysis for nonadherence using age, sex, and number of medications prescribed (both antihypertensives and non-antihypertensives separately) as independent predictors. Rates of nonadherence for individual antihypertensive drugs were calculated if prescribed to ≥10 patients.The overall rate of nonadherence to one or more prescribed antihypertensive medications was 40.3%. 14.4% of all patients were nonadherent to all prescribed antihypertensive medications (complete nonadherence), whereas 25.9% of all patients were nonadherent to at least 1, (but not all) prescribed antihypertensive medications (partial nonadherence). 72% of patients were prescribed ≥3 antihypertensives And for every increase in the number of antihypertensive medications prescribed, nonadherence increased with adjusted odds ratios of 2.9 (P < .001). Logistic regression showed that women were 3.3 times more likely to be nonadherent (P = .004). Polypharmacy (≥6 medications prescribed for hypertension and/or concomitant comorbidities) was prevalent in 52%. Bendroflumethiazide and chlortalidone demonstrated the highest and lowest nonadherences respectively (45.5% and 11.8%).Rate of nonadherence in patients with hypertension was significantly impacted by sex and number of antihypertensive medications prescribed. Understanding these factors is crucial in identifying and managing nonadherence.

Rifampicin reduces the plasma concentrations and the renin-inhibiting effect of aliskiren.

PURPOSE: This study aimed to investigate the effect of rifampicin, an inducer of CYP3A4 and P-glycoprotein, on the pharmacokinetics and pharmacodynamics of aliskiren, a renin inhibitor used in the treatment of hypertension. METHODS: In a randomized crossover study, 12 healthy volunteers took 600 mg rifampicin or placebo once daily for 5 days. On day 6, they ingested a single 150-mg dose of aliskiren. Plasma aliskiren concentrations were measured up to 72 h and urine concentrations up to 12 h; pharmacodynamic variables were measured up to 24 h. RESULTS: Rifampicin reduced the peak plasma aliskiren concentration (C(max)) by 39% (95% confidence interval 0.41, 0.90; P = 0.017) and the area under the plasma aliskiren concentration-time curve AUC(0-infinity) by 56% (95% confidence interval 0.35, 0.56; P < 0.001). Rifampicin had no significant effect on aliskiren elimination half-life (t(1/2)) or its renal clearance (Cl(renal)). Plasma renin activity 24 h after aliskiren intake was 61% higher during the rifampicin phase than during the placebo phase (P = 0.008). CONCLUSIONS: Rifampicin considerably reduces the plasma concentrations and the renin-inhibiting effect of aliskiren by decreasing its oral bioavailability.

Nonadherence to antihypertensive medications is related to pill burden in apparent treatment-resistant hypertensive individuals.

OBJECTIVE: Nonadherence to medication is present in at least 50% of patients with apparent treatment-resistant hypertension. We examined the factors associated with nonadherence as detected by a liquid chromatography-tandem mass spectrometry (LC-MS/MS)-based urine antihypertensive drug assay. METHODS: All urine antihypertensive test results, carried out for uncontrolled hypertension (BP persistently >140/90 mmHg) between January 2015 and December 2016 at a single toxicology laboratory were analysed. Drugs detected were compared with the antihypertensive drugs prescribed. Patients were classified as adherent (all drugs detected), partially nonadherent (at least one prescribed drug detected) or completely nonadherent (no drugs detected). Demographic and clinical parameters were compared between the adherent and nonadherent groups. Binary logistic regression analysis was performed to determine association between nonadherence and demographic and clinical factors. RESULTS: Data on 300 patients from nine hypertension centres across the United Kingdom were analysed. The median age was 59 years, 47% women, 71% Caucasian, median clinic BP was 176/95 mmHg and the median number of antihypertensive drugs prescribed was four. One hundred and sixty-six (55%) were nonadherent to prescribed medication with 20% of these being completely nonadherent. Nonadherence to antihypertensive medication was independently associated with younger age, female sex, number of antihypertensive drugs prescribed, total number of all medications prescribed (total pill burden) and prescription of a calcium channel blocker. CONCLUSION: This LC-MS/MS urine analysis-based study suggests the majority of patients with apparent treatment-resistant hypertension are nonadherent to prescribed treatment. Factors that are associated with nonadherence, particularly pill burden, should be taken into account while treating these patients.

Benefit of serum drug monitoring complementing urine analysis to assess adherence to antihypertensive drugs in first-line therapy.

With obesity having doubled in the last decade, hypertension is on the rise. In one-third of hypertensive patients the metabolic syndrome is present. This might be one factor for the increasing number of prescriptions for angiotensin receptor blockers and calcium-channel blockers besides a more favorable risk-to-benefit ratio. The aim of the present study was to evaluate a therapeutic drug monitoring (TDM) method for assessment of adherence based on cut-offs in inpatients and to compare it to an established urine drug screening in outpatients. A method for quantification of calcium-channel blockers and angiotensin receptor blockers using high-performance liquid chromatography-tandem mass spectrometric analysis (LC-MS/MS) was developed and validated. The method was applied to serum samples of 32 patients under supervised medication to establish cut-off values for adherence assessment based on dose-related concentrations (DRC, calculated from pharmacokinetic data). Furthermore, corresponding urine and blood samples of 42 outpatients without supervised medication were analysed and the results compared with regard to adherence assessment. All serum concentrations measured for amlodipine (n = 40), lercanidipine (n = 14), candesartan (n = 10), telmisartan (n = 4) and valsartan (n = 10) in inpatients were above the patient specific lower DRC confirming adherence. Of 42 outpatients the identification of analytes in urine as well as the quantification in serum exhibited differing results. According to urinalysis, adherence was demonstrated in only 87.0% of prescriptions, compared to 91.3% for serum analyses. Differences were observed for amlodipine, lercanidipine and candesartan which can be explained by a higher specificity of the serum analysis approach due to pharmacokinetics. The present study confirms that assessing adherence based on serum drug concentrations with individually calculated lower DRCs is more accurate than using qualitative urine analysis. In particular, drugs with low bioavailability, low renal excretion or high metabolism rate such as lercanidipine and candesartan may lead to underestimation of adherence via urine analysis.

Determination of enalapril maleate and atenolol in their pharmaceutical products and in biological fluids by flow-injection chemiluminescence.

A chemiluminescent method using flow injection (FI) was investigated for rapid and sensitive determination of enalapril maleate and atenolol, which are used in the treatment of hypertension. The method is based on the sensitizing effect of these drugs on the Ce(IV)-sulfite reaction. The different experimental parameters affecting the chemiluminescence (CL) intensity were carefully studied and incorporated into the procedure. The method permitted the determination of 0.01-3.0 microg mL(-1) of enalapril maleate in bulk form with correlation coefficient r = 0.99993, lower limit of detection (LOD) 0.0025 microg mL(-1) (S/N = 2) and lower limit of quantitation (LOQ) 0.01 microg mL(-1). The linearity range of atenolol in bulk form was 0.01-2.0 microg mL(-1) (r = 0.99989) with LOD of 0.0003 microg mL(-1) (S/N = 2) and LOQ of 0.01 microg mL(-1). In biological fluids the linearity range of enalapril maleate was 0.1-2.0 microg mL(-1) in both urine and serum, and for atenolol the linearity range was 0.1-1.0 microg mL(-1) in both urine and serum. The method was also applied to the determination of the drugs in their pharmaceutical preparations.

Morning surge in blood pressure and blood pressure variability in Asia: Evidence and statement from the HOPE Asia Network.

Hypertension is a major risk factor for cardiovascular and cerebrovascular diseases. To effectively prevent end-organ damage, maintain vascular integrity and reduce morbidity and mortality, it is essential to decrease and adequately control blood pressure (BP) throughout each 24-hour period. Exaggerated early morning BP surge (EMBS) is one component of BP variability (BPV), and has been associated with an increased risk of stroke and cardiovascular events, independently of 24-hour average BP. BPV includes circadian, short-term and long-term components, and can best be documented using out-of-office techniques such as ambulatory and/or home BP monitoring. There is a large body of evidence linking both BPV and EMBS with increased rates of adverse cardio- and cerebrovascular events, and end-organ damage. Differences in hypertension and related cardiovascular disease rates have been reported between Western and Asian populations, including a higher rate of stroke, higher prevalence of metabolic syndrome, greater salt sensitivity and more common high morning and nocturnal BP readings in Asians. This highlights a need for BP management strategies that take into account ethnic differences. In general, long-acting antihypertensives that control BP throughout the 24-hour period are preferred; amlodipine and telmisartan have been shown to control EMBS more effectively than valsartan. Home and ambulatory BP monitoring should form an essential part of hypertension management, with individualized pharmacotherapy to achieve optimal 24-hour BP control particularly the EMBS and provide the best cardio- and cerebrovascular protection. Future research should facilitate better understanding of BPV, allowing optimization of strategies for the detection and treatment of hypertension to reduce adverse outcomes.

Measuring adherence to therapy in apparent treatment-resistant hypertension: a feasibility study in Irish primary care.

BACKGROUND: Apparent treatment-resistant hypertension (aTRH) is defined as uncontrolled blood pressure (BP) in patients taking three or more antihypertensive medications. Some patients will have true treatment-resistant hypertension, some undiagnosed secondary hypertension, while others have pseudo-resistance. Pseudo-resistance occurs when non-adherence to medication, white-coat hypertension (WCH), lifestyle, and inadequate drug dosing are responsible for the poorly controlled BP. AIM: To examine the feasibility of establishing non-adherence to medication, for the first time in primary care, using mass spectrometry urine analysis. Operationalisation would be established by at least 50% of patients participating and 95% of samples being suitable for analysis. Clinical importance would be confirmed by >10% of patients being non-adherent. DESIGN AND SETTING: Eligible patients with aTRH (n = 453) in 15 university research-affiliated Irish general practices were invited to participate. METHOD: Participants underwent mass spectrometry urine analysis to test adherence and ambulatory BP monitoring (ABPM) to examine WCH. RESULTS: Of the eligible patients invited, 52% (n = 235) participated. All 235 urine samples (100%) were suitable for analysis: 174 (74%) patients were fully adherent, 56 (24%) partially adherent, and five (2%) fully non-adherent to therapy. A total of 206 patients also had ABPM, and in total 92 (45%) were categorised as pseudo-resistant. No significant associations were found between adherence status and patient characteristics or drug class. CONCLUSION: In patients with aTRH, the authors have established that it is feasible to examine non-adherence to medications using mass spectrometry urine analysis. One in four patients were found to be partially or fully non-adherent. Further research on how to incorporate this approach into individual patient consultations and its associated cost-effectiveness is now appropriate.

Separation and quantitation of several angiotensin II receptor antagonist drugs in human urine by a SPE-HPLC-DAD method.

In this work, an SPE-HPLC method coupled to photodiode array detection was validated in human urine matrix, in order to monitor four antihypertensive angiotensin II receptor antagonist drugs in patients under cardiovascular treatment. For that purpose, experimental design was used. Quantitation was accomplished by the internal standard method. The obtained LOQs were 95, 113, 125, and 85 ng/mL for eprosartan, telmisartan, irbesartan, and valsartan, respectively. The intraday and interday precision and accuracy at four concentration levels in the working range (LOQ-15 microg/mL) were always lower than 11% RSD and 8% relative error. The urine samples proved to be stable during 4 h at room temperature, after three thaw-freeze cycles, and for 2 months at -20 degrees C. No interferences from other endogenous compounds or co-administered drugs were found. The method has been successfully applied to monitor the renal elimination of eprosartan and valsartan during 24 h.

Medication adherence for resistant hypertension: Assessing theoretical predictors of adherence using direct and indirect adherence measures.

OBJECTIVES: This study examined theoretical predictors of long-term medication adherence (i.e., treatment-related beliefs, coherence of beliefs from experience with medication, habit strength, and pill burden) for patients with apparent treatment-resistant hypertension in primary care, using a composite adherence score derived from direct and indirect measures (i.e., prescription refill, self-report, and bioanalytical assays of urine). DESIGN: Cross-sectional study. METHODS: Individual patient records were screened for prescription refill adherence. Patients provided a urine sample for adherence screening and completed a battery of psychometric scales, including two self-report adherence measures (N = 204). Convergence of adherence measures was assessed, a composite adherence score was calculated, and hierarchical multiple regression was used to examine the role of theoretical predictors of adherence. RESULTS: Non-adherence estimates ranged from 20.3 to 41.1%, depending on the assessment method used. Associations among adherence measures were weak to moderate (ρ = .00-.53). Medication-taking habit strength was the strongest predictor of adherence, explaining 19% incremental variance in adherence beyond treatment-related beliefs. Beliefs and coherence did not predict adherence, even for patients with weaker habits. Pill burden was not associated with habit strength or adherence for this sample. CONCLUSIONS: Associations among unique adherence measures were weak overall, providing further evidence that multiple measures are necessary to accurately assess adherence. Habit strength is a key predictor of adherence for chronic conditions. Both habit strength and pill burden represent important intervention targets for improving long-term medication adherence. Longitudinal inception studies are needed to properly test Common-Sense Model propositions and elucidate the role of beliefs, coherence, and habits in predicting adherence at various stages of the chronic illness trajectory. Statement of contribution What is already known on this subject? Non-adherence to antihypertensives is a leading cause of apparent treatment-resistant hypertension (aTRH). Behaviour maintenance (vs. initiation) factors may be more predictive of long-term adherence. What does this study add? Associations among direct and indirect measures of adherence are generally weak. Habit strength is the strongest predictor of long-term adherence for aTRH in primary care. Inception studies are needed to further validate Common-Sense Model propositions.