The Pharmacokinetics of Nifedipine Controlled Release Tablets in Hypertensive Patients on Hemodialysis

Calcium channel blockers are widely used to reduce blood pressure in hypertensive patients on hemodialysis. They are useful I patients with left ventricular hypertrophy, diastolic dysfunction and stable angina pectoris. Adalat GITS, a long-acting dihydropyridine calcium channel blocker, has been used as one of first choices to treat the hypertension because of its effective hypotensive potency and relative absence of side effects compared with the short-acting agent. Antihypertensive effects of calcium channel blockers largely depend on their plasma concentrations, a rapid increase in blood pressure may occur as circulating levels of such blockers decrease after hemodialysis. This rapid fluctuation in blood pressure may evoke rapid alteration in hemodynamics. Luik et al. show that pre- or post-dialysis blood pressure measurements in patients with hemodialysis may be misleading for determining the blood pressure. Ambulatory pressure monitoring (ABPM) may be more useful for estimating blood pressure control in the dialysed patients. For most patients on dialysis, the goal office blood pressure is less than an average value below 150/90 mmHg on no medication. The reasonable target goal of mean ambulatory blood pressure is less than 135/85 mmHg during the day and less than 120/80 mmHg at night.

There is need of more convincing data to demonstrate the effect of Adalat GITS on hemodialytic patients by using ABPM and investigating the plasma concentrations. This study was designed to investigate effects of Adalat GITS on hemodialytic blood pressures in patients with chronic hemodialysis by using ABPM and measuring the drug plasma concentrations.

This is a prospective, open, non-randomized, non-controlled study. 20 patients with hypertension on chronic maintenance hemodialysis will be enrolled in the study. All patients had mild to moderate hypertension and are receiving antihypertensive agents.

All antihypertensive agents received by patients screened were withdrawn and patients are assigned to receive only nifedipine controlled release tablets 60mg/day. The agents are given orally once a day at 08:00h and patients are followed for at least 4 weeks. After 4 weeks of antihypertensive treatment, 20 patients with adequate blood pressure achieved (pre-hemodialysis office blood pressure \< 140/90 mmHg) will be recruited into the study. If adequate blood pressure is not achieved, the patients will be excluded.

After patients have achieved adequate blood pressure (pre-hemodialysis office blood pressure \< 140/90 mmHg) at enrollment, 24-hour ambulatory blood pressure monitoring (ABPM) is immediately performed on the day of hemodialysis within the subsequent two days. The administration of Adalat will continue as previously until the morning of the hemodialytic day with AMPM and blood samplings for study. The blood was sampled just before, 1 hour after, 2 hour after and 3 hour after the start of hemodialysis, and immediately after hemodialysis to measure circulating levels of nifedipine and the corresponding time points on the next hemodialysis-free day.

The 24-hour ABPM is performed in each enrolled patient on the day of hemodialysis. The monitoring is started at 08:00 h when the drugs are given. The device is programmed to measure blood pressure every 30 min (from 08:00 h to 21:00 h) and every 60 min (from 21:00 h to 08:00 h).