How long will it take for hydrochlorothiazide (HCTZ) to lower my blood pressure?

Diuresis from hydrochlorothiazide (HCTZ) begins within two hours of an oral dose.^1-4 HCTZ reaches maximum bioavailability in four to six hours.^1,2,4

Studies show the maximum antihypertensive effects of HCTZ are evident about four weeks into treatment.^5,6 A 2010 meta-analysis of 108 clinical trials of the dose-response characteristics of HCTZ on systolic blood pressure showed the maximum effects at a typical starting dose of 12.5 to 25 mg HCTZ was reached by four weeks.⁷

^References

1. Carter BL, Ernst ME, Cohen JD. Hydrochlorothiazide versus chlorthalidone: evidence supporting their interchangeability. Hypertension 2004; 43 (1): 4-9.
2. Giudicelli JF, Richer C, Mattei A. Pharmacokinetics and biological effects of captopril and hydrochlorothiazide after acute and chronic administration either alone or in combination in hypertensive patients. Br J Clin Pharmacol 1987; 23 Suppl 1: 51s-63s.
3. Jordo L, Johnsson G, Lundborg P, Persson BA, Regardh CG, Ronn O. Bioavailability and disposition of metoprolol and hydrochlorothiazide combined in one tablet and of separate doses of hydrochlorothiazide. Br J Clin Pharmacol 1979; 7 (6): 563-567.
4. Hydrochlorothiazide [package insert]. Morgantown, WV: Mylan Pharmaceuticals, Inc.; 2011.
5. Pareek AK, Messerli FH, Chandurkar NB, et al. Efficacy of low-dose chlorthalidone and hydrochlorothiazide as assessed by 24-h ambulatory blood pressure monitoring. J Am Coll Cardiol 2016; 67 (4): 379-389.
6. Ernst ME, Carter BL, Goerdt CJ, et al. Comparative antihypertensive effects of hydrochlorothiazide and chlorthalidone on ambulatory and office blood pressure. Hypertension 2006; 47 (3): 352-358.
7. Ernst ME, Carter BL, Zheng S, Grimm RH, Jr. Meta-analysis of dose-response characteristics of hydrochlorothiazide and chlorthalidone: effects on systolic blood pressure and potassium. Am J Hypertens 2010; 23 (4): 440-446.