With the advent of long-acting or slow-release antihypertensive drugs, we should be aware of a fall in nighttime blood pressure (BP) as well as daytime blood pressure. In the present study, casual BPs at the physician's office as well as ambulatory BP was recorded every hour throughout 24 hours with a noninvasive automated BP monitoring device in 24 essential hypertensives treated with slow-release nifedipine. Administration of slow-release nifedipine (20-40mg, b.i.d.) decreased not only casual BPs but also ambulatory mean BP during the whole day or daytime (6 am to 10 pm). Slow-release nifedipine at 10mg in the morning did not affect casual BPs at the office. However, mean BP obtained by ambulatory BP monitoring during the daytime was significantly attenuated.In addition, a profound fall in mean BP amounting to more than 20mmHg during the night in some of the patients was observed during treatment with slow-release nifedipine not only at 20-40mg (b.i.d.) but also at 10mg once a day.
These results suggest that we have to take into consideration the possibility that long-acting hypotensive agents may cause a great fall in nighttime BP during sleep, especially in the elderly.