BACKGROUND: Therapeutic drug monitoring (TDM) involves the measurement of serum drug concentrations to optimize pharmacotherapy. Traditionally, blood pressure measurements alone, and not TDM, have been used to evaluate the antihypertensive drug response. However, approximately 50 % of hypertensive patients treated with lifestyle changes and antihypertensive drugs fail to achieve blood pressure control. Serum drug concentration measurements could be useful to select the optimal drugs in adjusted doses and to identify non-adherence. Implementation of TDM in clinical routine for antihypertensive drugs depends on established serum reference ranges. METHODS: Commonly used antihypertensive drugs were identified based on prescription data. The authors performed a review of authoritative literature on reported serum drug concentrations and calculated expected concentrations from previously reported pharmacokinetic parameters with commonly prescribed daily doses. Finally, serum drug concentrations in samples from patients undergoing antihypertensive treatment were measured. RESULTS: Serum reference ranges for 24 frequently used antihypertensive drugs were established based on results from three approaches. CONCLUSION: Serum drug concentration measurements, interpreted in light of the established reference ranges, together with blood pressure measurements and other clinical data, may help identify non-adherent patients and tailor individual antihypertensive treatment when deviant drug responses appear, in line with the concept of personalized medicine.
Nonadherence to drugs is a challenge in hypertension treatment. We aimed to assess the prevalence of nonadherence by serum drug concentrations compared with 2 indirect methods and relate to the prescribed drug regimens in a nationwide multicenter study. Five hundred fifty patients with hypertension using ≥2 antihypertensive agents participated. We measured concentrations of 23 antihypertensive drugs using ultra high performance liquid chromatography tandem mass-spectrometry and compared with patients’ self-reports and investigators’ assessment based on structured interview. We identified 40 nonadherent patients (7.3%) using serum drug concentrations. They had higher office diastolic blood pressure (90 versus 83 mm Hg, P <0.01) and daytime diastolic blood pressure (85 versus 80 mm Hg, P <0.01) though systolic blood pressures did not differ significantly. They had more prescribed daily antihypertensive pills (2.5 versus 2.1 pills, P <0.01) and total daily pills (5.5 versus 4.4 pills, P =0.03). Prescription of fixed-dose combination pills were lower among the nonadherent patients identified by serum concentrations (45.0 versus 67.1%, P <0.01). Fifty-three patients self-reported nonadherence, while the investigators suspected 69 nonadherent patients. These groups showed no or few differences in drug regimens, respectively. In summary, we detected 7.3% prevalence of nonadherence by serum drug measurements in patients using ≥2 antihypertensive agents in a nationwide study; they had higher office and ambulatory diastolic blood pressures, higher number of prescribed daily pills, more daily antihypertensive pills, and less frequent prescriptions of fixed-dose combination pills. Indirect methods showed poor overlap with serum drugs concentrations and no or minimal medication differences. Thus, serum measurements of drugs were useful in detection and characterization of nonadherence to antihypertensive treatment. REGISTRATION: URL: https://www.clinicaltrials.gov ; Unique identifier: NCT03209154.
A standard fixed dosing regimen (S) and a variable dosing regimen (VD) of naproxen for patients with knee and hip osteoarthritis were compared in a multicentre, open, controlled, parallel 8-week trial. The daily dose of naproxen (Naprosyn) in the S-group was 500-1000 mg, in VD maximum daily dose was 1000 mg. The number of patients entering the study was 396 (286 females). Mean (SD) age was 67 (10) and 67 (11) years in the S- and VD-groups respectively. The number of patients available for efficacy analyses, including the withdrawals, was 356. Efficacy measures included pain on movement, night pain, morning stiffness, a functional index and patient's and doctor's overall assessments. Similar improvement was seen in both groups. The number of patients withdrawn due to adverse reactions in S and VD was 35 and 23 respectively (p less than 0.05). Group differences in drug consumption were highly significant (p less than 0.01) with a 20-30% lower consumption in the VD-group. Thus, similar efficacy and possibly better tolerance was obtained with a lower drug consumption by a variable dosing regimen compared to a fixed regimen.
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