Crossover study of amlodipine versus nifedipine CR with home blood pressure monitoring via cellular phone: internet-mediated open-label crossover trial of calcium channel blockers for hypertension (i-TECHO trial)

OBJECTIVE: We developed a new data collection system named i-converter that could transmit data to a website via cellular phone. Using the system, we compared the effects of two calcium channel blockers on the home blood pressure. METHODS: Amlodipine and nifedipine CR were administered to 41 patients with essential hypertension for more than 6 weeks each in a randomized open-label crossover study. The dose of each drug was increased until the home blood pressure reached the target level of under 135/85 mmHg. RESULTS: The morning home systolic and diastolic blood pressures were significantly lower during nifedipine CR treatment: 133 +/- 10/81 +/- 8 mmHg with amlodipine versus 131 +/- 8/80 +/- 8 mmHg with nifedipine CR, P < 0.05. The morning pulse rate was significantly higher during nifedipine CR treatment (69 +/- 9 beats/min with amlodipine versus 70 +/- 9 beats/min with nifedipine CR, P < 0.05). The evening home blood pressure and pulse rate, however, showed no significant differences between the two drugs (128 +/- 11/74 +/- 7 mmHg and 74 +/- 10 beats/min with amlodipine versus 128 +/- 10/75 +/- 7 mmHg and 74 +/- 9 beats/min with nifedipine CR, all not significant). CONCLUSIONS: Nifedipine CR had a stronger antihypertensive effect than amlodipine during the critical morning period, but the morning pulse rate was higher. Our new data transmission system was effective for collecting precise data on the blood pressure and pulse rate via the internet.