Pharmacokinetic properties of isradipine after single-dose and multiple-dose oral administration in Chinese volunteers: a randomized, open-label, parallel-group phase I study.

Isradipine could be used for the treatment of high blood pressure or Parkinsonism, yet the study on pharmacokinetics (PK) of isradipine is lacking in the Chinese population. The current study aims to assess the dose proportionality, pharmacokinetics and gender effect of isradipine following oral single and multiple doses in Chinese subjects. A randomized, open-label, parallel-group trial was conducted in 30 healthy Chinese volunteers. Subjects randomly received a single dose of 2.5, 5 or 10 mg, and multiple doses (2.5 mg) of isradipine. Blood samples were collected pre-dose (0 h) and 0.33, 0.67, 1, 1.5, 2, 3, 4, 6, 9, 12, 24, 36 and 48 h post-dose. Isradipine was rapidly absorbed with the time to maximum concentration <1.27 h for all dosage groups. The maximum concentrations were 2.46, 5.34, 10.93 and 3.32 ng/mL and area under the concentration-time curve from time zero to the last time point (AUClast ) were 7.05, 12.58, 24.68 and 5.31 ng/ml · h for the 2.5, 5 and 10 mg single-dose and 2.5 mg multiple-dose groups, respectively. The half-life ranged from 5.76 to 7.94 h. The maximum concentration and AUC were found to increase linearly and dose-dependently for isradipine. No statistical gender differences were found. These findings indicated that the pharmacokinetic parameters of isradipine in Chinese population were dose-proportional and predictable over a range of 2.5-10 mg isradipine oral doses.