Background: S-amlodipine gentisate, consisting entirely of the (S)-enantiomer, was developed to increase the potency and improve the safety profile of amlodipine. Regulatory requirements for marketing of S-amlodipine gentisate in Korea require comparison of this agent versus amlodipine racemate.
Objective: This study was conducted to compare the pharmacodynamic (PD) and pharmacokinetic (PK) characteristics of the S-amlodipine formulation (S-amlodipine gentisate) and amlodipine racemate (amlodipine besylate).
Methods: This study consisted of 2 separate substudies; PD and PK parameters were evaluated separately. Both studies were conducted using a doubleblind, randomized, 2-period, 2-treatment, 2-sequence, double-dummy, single-dose crossover design with S-amlodipine 5 mg and amlodipine racemate 10 mg, separated by a 2-week washout period. Blood pressure (BP) and heart rate were measured in the sitting position before dosing and at 1, 2, 4, 5, 6, 7, 8, 10, 12, 14, 24, 48, and 72 hours after oral administration of S-amlodipine or amlodipine racemate. Impedance cardiography parameters (stroke volume, cardiac index, and systemic vascular resistance) were measured before and at 1, 2, 4, 5, 6, 7, 8, 10, and 12 hours after dosing. For PK assessments, serial blood samples were collected before dosing and at 1, 2, 4, 6, 8, 10, 12, 14, 24, 48, 72, 96, 120, 144, and 168 hours after dosing, and drug concentrations were determined by HPLC-MS/MS. Adverse events (AEs) were collected using self-report or general health-related questions.
Results: The PD study included 24 healthy men (mean [SD] age, 23.1 [3.1] years; weight, 69.2 [6.1] kg), and the PK study included 24 different healthy men (mean age, 25.1 [2.1] years; weight, 65.9 [5.9] kg). There were no statistically significant differences between the treatment groups in terms of systolic BP, diastolic BP, or heart rate by repeated-measures ANOVA. Likewise, in the analysis of impedance cardiography, the treatment groups did not display any significant differences in stroke volume, cardiac index, or systemic vascular resistance by repeatedmeasures ANOVA. The mean (SD) AUC(0-last) was 129.7 (62.8) ng . h/mL after dosing with S-amlodipine and 129.0 (59.6) ng . h/mL after dosing with amlodipine racemate. The geometric mean ratio (S-amlodipine: amlodipine racemate) of the S-amlodipine AUC(0-last) was 1.01 (90% CI, 0.90-1.13). In the PD study, 4 AEs in 3 volunteers (3/24; 12.5%) and 8 AEs in 5 volunteers (5/24; 20.8%) were reported after dosing with S-amlodipine and amlodipine racemate, respectively. In the PK study, 18 AEs in 11 volunteers (11/24; 45.8%) and 20 AEs in 9 volunteers (9/24; 37.5%) were reported after dosing with S-amlodipine and amlodipine racemate, respectively. Five volunteers reported AEs after dosing with both S-amlodipine and amlodipine racemate. For the PD and PK studies combined, 30 AEs were judged to be possibly related to S-amlodipine (16 cases) or amlodipine racemate (14 cases). Twenty AEs were judged not to be related to S-amlodipine (6 cases) or amlodipine racemate (14 cases). The most common AEs considered at least possibly related to the study drug in both studies were headache (18 cases) and nausea (3 cases).
Conclusions: In these single-dose studies, no significant differences were found in PD (hemodynamic) or PK parameters between S-amlodipine 5 mg and amlodipine racemate 10 mg. S-amlodipine had a safety profile comparable to that of amlodipine racemate in these healthy male volunteers.