Results of a phase III, 8-week, multicenter, prospective, randomized, double-blind, parallel-group clinical trial to assess the effects of amlodipine camsylate versus amlodipine besylate in Korean adults with mild to moderate hypertension

BACKGROUND: Amlodipine besylate has been used in Korea for the treatment of hypertension for >17 years, with well-established efficacy and tolerability. Amlodipine camsylate is a newer formulation developed for generic use. It has been assessed in terms of physical stability and pharmacokinetic and pharmacodynamic properties and been found to be effective in lowering blood pressure in preclinical and Phase I and II trials. However, to date, no studies have compared the clinical effectiveness of amlodipine camsylate and amlodipine besylate in treating hypertension. OBJECTIVE: This study was designed to determine the effectiveness and tolerability of amlodipine camsylate compared with amlodipine besylate in Korean patients with mild to moderate hypertension. METHODS: This Phase III, 8-week, prospective, randomized, double-blind, parallel-group study was conducted in 13 cardiology centers across the Republic of Korea. Male and female Korean patients aged 18 to 75 years having uncomplicated, mild to moderate, essential hypertension (sitting diastolic blood pressure [SiDBP] 90-<110 mm Hg) and receiving no antihypertensives in the 2 weeks before randomization were eligible. Patients were randomly assigned to receive oral treatment with amlodipine camsylate or amlodipine besylate. For the first 4 weeks, patients received amlodipine 5 mg QD (morning). After 4 weeks, if either blood pressure was > or =140/ > or =90 mm Hg or SiDBP had not decreased by > or =10 mm Hg from baseline, the dose of amlodipine was increased to 10 mg QD for 4 weeks. Trough blood pressure and heart rate were measured in duplicate with the patient in the sitting position at each clinic visit (baseline [week 0] and weeks 4 and 8 of treatment); mean values were calculated and recorded. At weeks 4 and 8, tolerability was assessed using history taking and laboratory analysis, and compliance was assessed using pill counts. The primary end point was change from baseline in SiDBP at week 8. Secondary end points were change from baseline in sitting systolic blood pressure (SiSBP) at week 8 in the total population and in the subgroup of patients who had previously received antihypertensive treatment versus those who had not. RESULTS: A total of 189 patients were enrolled (mean age, 53 years; 105 women, 84 men; mean body weight, 65.8 kg). One patient in the amlodipine camsylate group dropped out of the study at week 0 of treatment (this patient did not use any study medication) and was excluded from the modified intent-to-treat (ITT) analysis. Thus, 188 patients were treated and included in the ITT analysis (94 patients per treatment group; ITT analysis); 161 patients were included in the perprotocol (PP) analysis (n = 80 for amlodipine camsylate, n = 81 for amlodipine besylate) (14 patients in the amlodipine camsylate group and 13 patients in the amlodipine besylate group were excluded from the PP analysis due to consistent withdrawal or protocol violation). Mean (SD) SiSBP and SiDBP were significantly decreased from baseline in both groups (amlodipine camsylate, from 146.7 [12.3]/96.6 [5.4] to 127.9 [14.8]/83.4 [7.7] mm Hg [both, P < 0.001]; amlodipine besylate, from 146.8 [12.8]/96.7 [5.1] to 128.0 [10.1]/83.8 [7.5] mm Hg [both, P < 0.001]). The differences in SiSBP/SiDBP between the 2 groups at week 8 were not significant. The SiDBP response rates in the subgroups that had and had not been previously treated with antihypertensives were statistically similar (56/69 [81.2%] and 83/92 [90.2%], respectively). The prevalences of clinical adverse events (AEs) were not significantly different between the 2 treatment groups (amlodipine camsylate, 27.3 %; amlodipine besylate, 28.7%). The most common AEs were dizziness and dyspnea (both in 3/94 [3.2%] and 1/94 [1.1%] patients who received amlodipine camsylate and amlodipine besylate, respectively). CONCLUSION: The effectiveness and tolerability of amlodipine camsylate were not significantly different from those of amlodipine besylate in these Korean adults with mild to moderate hypertension.