A newly developed calcium channel blocker, NB-818, was given orally at a dosage of 10 mg b.i.d. to 8 healthy adult male volunteers (active drug, 6; placebo, 2) to investigate it for safety, tolerability and pharmacokinetic profile. The following results were obtained.

1) Subjective and objective symptoms such as postural light-headedness, facial flushing, migraine and insomnia were observed. These symptoms were slight and transient. There were no remarkable laboratory test abnormalities.

2) As to blood pressure, significant reductions were seen at some points on day 2. No marked change in heart rate was observed.

3) The time-plasma concentration curve on day 1 was similar to that on day 7, and no significant change in pharmacokinetic parameters was observed between day 1 and day 7. Therefore, there was no substantial accumulation of NB-818 in plasma ascribable to the multiple dosing.

4) No unchanged NB-818 was detected in the urine. It is concluded from these results that NB-818 is safe and well tolerated in healthy adult male volunteers.