S-amlodipine plus chlorthalidone vs. S-amlodipine plus telmisartan in hypertensive patients unresponsive to amlodipine monotherapy: Study protocol for a randomized controlled trial

Sang Ho Jo, Sung Ji Park, Eung Ju Kim, Soo Joong Kim, Hyun Jae Cho, Jong Min Song, Jinho Shin, Jin Joo Park, Joon Han Shin, Kyoo Rok Han, Dong Ju Choi

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Background: The efficacy of a combination of a calcium channel blocker (CCB) plus chlorthalidone (diuretic) versus a CCB plus an angiotensin receptor blocker (ARB) in patients not responding to CCB monotherapy has not been evaluated previously. We plan to compare the efficacy and safety of S-amlodipine (CCB) plus chlorthalidone versus S-amlodipine plus telmisartan (ARB) combinations among hypertension patients unresponsive to amlodipine monotherapy. Methods/design: This study is a prospective, randomized, double-blind, multicenter, parallel, non-inferiority phase 4 study. Hypertension patients who have been treated with amlodipine (5 mg) or S-amlodipine (2.5 mg) monotherapy for ≥2 weeks and whose mean diastolic blood pressure (DBP) is greater than 90 mmHg will be randomized to either S-amlodipine (2.5 mg) plus chlorthalidone (25 mg) or S-amlodipine (2.5 mg) plus telmisartan (40 mg) therapy. The primary efficacy endpoint is mean sitting DBP change after 12 weeks of treatment. The study objective is to prove the non-inferiority of the former combination (test drug) as compared to the latter one (control) with a non-inferiority margin of 3 mmHg in mean DBP change. The secondary endpoints are 6-week DBP change, 6- and 12-week sitting systolic BP (SBP) change, and the attainment of the target BP (SBP < 140 mmHg or DBP < 90 mmHg). Urine albumin, albumin/creatinine ratio (ACR), pulse wave velocity, central BP, 24-h ambulatory BP monitoring, and body fluid composition analysis will be performed at each hospital's discretion. The sample size was estimated as 170 in total with 1:1 randomization. Discussion: This is the first study comparing the efficacy of a CCB plus chlorthalidone versus a CCB plus an ARB in patients who are not responding to CCB single therapy. The study result will help clinicians to choose between chlorthalidone and telmisartan in CCB-unresponsive patients.

Original languageEnglish
Article number324
Issue number1
Publication statusPublished - 2018 Jun 20



  • Angiotensin receptor blocker
  • Calcium channel blocker
  • Combination
  • Hypertension

ASJC Scopus subject areas

  • Medicine (miscellaneous)
  • Pharmacology (medical)

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