Effect of calcium and or hydrochlorothiazide on 24-hour blood pressure in patients with primary hypertension

Abstract

The purpose of this study was to examine the single and combined effects of calcium and hydrohlorothiazide (HCTZ) on 24-hour blood pressure and the relationship between 24-hour sodium and calcium urinary exretion and 24-hour blood pressure control using ambulatory blood pressure monitoring (ABPM) machine. The study was achieved in twenty-five mild to moderate hypertensive patients in out-patient department at King Chulalongkorn Memorial Hospital. They were randomly allocated into two regimens, twelve patients were assigned to reeive HCTZ 25 mg once daily as the first drug while thirteen patients were assigned to receive CaCo2 1 gm twice daily (elemental calcium 800mg/d) as the first drug. Four weeks later, CaCO3 1 gm BID was added into the therapy for group 1, while HCTZ 25 mg OD was added into the therapy for group 2 for another 4 weeks. The office BP, 24-hour ambulatory BP and 24-hour urine collection were monitor at the end of each period. HCTZ 25mg OD could significantly reduce BP of the patients throughout 24-hour in both mild and moderate hypertensive patients, in non-dipper and especially in dipper group. DBP was slightly higher reduced than SBP. BP loads were similarly reduced in the same group of patients. CaCo3 caused higher reduction in DBP than SBP especially in mild hypertensive and/or non-dipper patients while in dipper group it seem to cause more redution during day-time than night-time. BP loads were reduced in the same way as blood pressure. When CaCo3 was used as a second drug combined with HCTZ, there were increment in BP and BP loads reductions especially during night-time in mild hypertensive and/or non-dipper group while no further BP and BP loads reductions were found in moderate hypertensive and/or dipper group. When HCTZ was used in combination with CaCO3, the increment of BP and BP loads reduction was much less than when HCTZ was used as the first drug. Greater rate of response and higher percentage of normalized of normalizedpatients were found after treatment with the combination drugs. HCTZ 25 mg per day alone or used in combination with CaCo3, the nocturnal decline of BP were increased in moderate hypertensive and/or non-dipper patients, the circadian rhythm of blood pressure of non-dippers might be transformed to dipper patterns. CaCo3 alone could increased nocturnal decline of BP only in mild hypertensive and/or non-dipper group. In contrary, in dipper group, the nocturnal decline of BP not only not increased but even became lower than baseline, the BP pattern of some dippers was therefore was change to non-dipper. After HCTZ was added to the therapy with CaCO3, the increment of nocturnal decline of BP were increased in all groups of patients, the BP pattern was thus changed back to dipper type. 24-hour urinary sodium excretions were increased after treatment with HCTZ either alone or combined to CaCO3, especially in moderate hypertensive patients. In contrary, when CaCO3 was used as the first drug and HCTZ was added to thetherapy, the 24-hour urinary sodium excretion were decreased in both mild and moderate hypertensive patients. 24-hour urinary sodium excretion of non-dippers were lower while the excretion of calcium were highers as compared to dippers. Sodium excretion in non-dipper were increased after treatment with HCTZ or CaCO3 alone and when used the two drughs in combination, howere, in dippers, the increment in sodium excretion was found only after treatment with HCTZ alone.