Abstract
Background: The duration of the QT interval as measured by 12-lead electrocardiography is a measure of myocardial repolarization and is widely used to describe cardiac abnormalities, to determine the presence of cardiac toxicity and to evaluate drug safety. In hypertension, the QT interval is a predictor of the risk of both coronary events and cardiovascular death, after adjusting for the effects of additional risk factors. According to AHA and JNC VIII calcium channel blockers are first-line drug in the treatment of hypertension. The equipotent antihypertensive effect of cilnidipine and amlodipine in their equivalent dose has been demonstrated in number of studies.

Aims and Objectives: To compare and evaluate the effects of calcium channel antagonists amlodipine and cilnidipine on QT interval among hypertensive patients.

Materials and Methods: A total of 258 patients were screened, examined, and enrolled as study participants during that period. The enrolled patients were then divided as (1) hypertensive patient (n = 159) - selected patients received either amlodipine (2.5–10 mg) or cilnidipine (5–20 mg) with or without angiotensin receptor blocker (ARB) and (2) hypertensive with controlled diabetic patients (n = 99) - selected patients received either amlodipine (2.5–10 mg) or cilnidipine (5–20 mg) with or without ARB along with antidiabetic medication. Calculated by Bazett’s formula (most commonly used) = QT Interval/√ (relative risk [RR] interval) where RR interval = 60/heart rate, normal QTc ≤440 ms. The QT interval was measured at the baseline and after 12 months of treatment for hypertensive patients.

Results: There was extremely significant QTc reduction was seen with cilnidipine therapy and significant elevation seen by amlodipine treatment but without any clinical relevance. While comparing the effect of amlodipine and cilnidipine, extremely significant as well as clinically relevant difference between the two treatments was noted.

Conclusions: From this study, it can be concluded that cilnidipine reduces QTc interval, and hence is a better choice over amlodipine for patients suffering from long QT interval.