Pharmacokinetic and pharmacodynamic correlation of plasma concentrations and blood pressure in hypertensive patients: A study

Objective: The aim of this study was to determine the correlation between the pharmacokinetic (PK) parameter (plasma concentration) and pharmacodynamic (PD) parameter (blood pressure [BP]) in hypertensive patients on metoprolol therapy. Materials and Methods: High‑performance liquid chromatography (HPLC) method for the measurement of plasma concentrations was developed and validated, following which the Ethical Committee approval was obtained. Patients admitted with hypertension and above 18 years of age were randomized into two groups based on the time of administration of metoprolol. Patients for whom metoprolol therapy was contraindicated were excluded from the study. Results: One hundred and six patients were enrolled in the study; patients with 61–70 years formed majority, 51.8% of males were associated with hypertension compared to 48.2% of the females. Patients receiving morning dose of the drug showed higher plasma concentrations in comparison with evening dose. PK and PD correlation was carried out and correlation coefficient “R2” was calculated by the formula y = mx + c. For systolic BP of morning administration, R2 for peak concentration was found to be 0.913 and R2 for trough concentration was found to be 0.903. R2 value for diastolic BP of morning administration was found to be 0.873 for peak concentration and 0.969 for trough concentration. Systolic BP of evening exhibited R2 value of 0.986 and 0.955 for peak and trough concentrations, respectively. Diastolic BP of evening showed R2 value of 0.931 and 0.896 for peak and trough concentrations. Statistical analysis was done using Pearson’s correlation test, and it was observed that there is a significant correlation (P < 0.001) between the plasma concentrations and BP. Conclusion: The PK and PD parameters are at par with each other. It can be concluded that there is a significant correlation between the BP and plasma concentrations. This can be considered as the preliminary finding to ascertain the various PK parameters to optimize the dosing schedule for hypertensive patients.