How long will it take for chlorthalidone to lower my blood pressure?

Pharmacologic studies have determined that the onset of action for chlorthalidone after oral administration begins in about two to three hours with a half-life of 40-60 hours and with chronic dosing, it may persist for up to 72 hours.^1-3 The manufacturer’s information states that the diuretic effect of chlorthalidone occurs in approximately 2.6 hours.⁴ The long duration of effect for chlorthalidone differentiates this medication from hydrochlorothiazide (HCTZ), which has a half-life of approximately 8-15 hours, and may account for some of the differences in outcomes that have been observed with chlorthalidone.⁵

Further, studies using ambulatory blood pressure monitoring have demonstrated that the antihypertensive effects of chlorthalidone persist throughout the day and night.^6,7 These studies also illustrate that maximum blood pressure effects are evident about four weeks into treatment.^6,7

^References

1. Carter BL, Ernst ME, Cohen JD. Hydrochlorothiazide versus chlorthalidone: evidence supporting their interchangeability. Hypertension. 2004;43(1):4-9.
2. Riess W, Dubach UC, Burckhardt D, Theobald W, Vuillard P, Zimmerli M. Pharmacokinetic studies with chlorthalidone (Hygroton) in man. Eur J Clin Pharmacol. 1977;12(5):375-382.
3. Fleuren HL, Thien TA, Verwey-van Wissen CP, van Rossum JM. Absolute bioavailability of chlorthalidone in man: a cross-over study after intravenous and oral administration. Eur J Clin Pharmacol. 1979;15(1):35-50.
4. Chlorthalidone Manufacturers Information. Morgantown, WV: Mylan Pharmaceuticals, Inc.; 2014.
5. Sica DA. Chlorthalidone: has it always been the best thiazide-type diuretic? Hypertension. 2006;47(3):321-322.
6. 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.
7. 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.