The Korean Pharmacopoeia(KP) is the standard for pharmaceutical quality control, significantly impacting the pharmaceutical industry. The current KP contains more than 2,000 monographs with different dates of enactment and revision, including methods that may not align with changes in the industry. In particular, the titration method using indicators is difficult to ensure accuracy and consistency of test results because it is judged visually.In this study, we improved accuracy and precision by changing the indicator-based assay method to potentiometric titration. Five APIs—isoniazid, caffeine anhydrous, caffeine hydrate, chlorpheniramine maleate, and tifepidine hibenzate—were selected for the study items, which were reported to be in urgent need of revision in the pharmaceutical field. The established method using 0.1 M perchloric acid as titrant was fully validated. All five APIs showed specific and selective responses without interference at constant potentials. Linearity was confirmed in the range of 80~120% of test solution concentration (R2=0.9996~1.000). Accuracy (99.5~100.5%) and precision (0.0~0.08%) also met within standards, suggesting that it could replace outdated test methods.Based on these results, revised monographs for the five APIs were prepared, and it is expected that this will increase the usability of the KP by providing modernized test methods and contribute to improving the quality control level and quality of distributed pharmaceuticals.