Treatment with low-dose chlorthalidone, 6.25 mg daily, significantly reduced mean 24-h ABP as well as daytime and nighttime BP. Due to its short duration of action, no significant 24-h ABP reduction was seen with HCTZ, 12.5 mg daily, which merely converted sustained hypertension into masked hypertension. Thus, low-dose chlorthalidone, 6.25 mg, could be used as monotherapy for treatment of essential hypertension, whereas low-dose HCTZ monotherapy is not an appropriate antihypertensive drug. (Comparative Evaluation of Safety and Efficacy of Hydrochlorothiazide CR with Hydrochlorothiazide and Chlorthalidone in Patients With Stage I Essential Hypertension; CTRI/2013/07/003793).