LOw DosE Spironolactone, chlorThAlidone oR Combination in CKD Trial

The purpose of this research is to gather information on the safety and effectiveness of spironolactone and chlorthalidone for treatment of high blood pressure in patients with moderate to advanced CKD. Both drugs have been approved by the Food and Drug Administration (FDA) for the treatment of high blood pressure since 1960.

Inclusion Criteria: * Study is limited to US Veterans * GFR estimated by race-independent CKD-EPI formula \< 45 ml/min/1.73m2 but 15 mL/min/1.73m2 * Hypertension * The investigators will use clinic AOBP of at least 135/85 to define hypertension * Treatment with antihypertensive drugs * This would require the use of at least one antihypertensive drug * One of the drugs should be either an ACE inhibitor or ARB or a beta-blocker at the time of randomization * Serum K 3.5 to 5.2 mEq/L at the time of randomization Exclusion Criteria: * Clinic AOBP of \>=160/100 mmHg * Use of: * SPL * eplerenone * amiloride * triamterene * finerenone * thiazide * thiazide-like drugs (CTD, HCTZ, metolazone, indapamide) or the use of K binders or fludrocortisone in the previous 4 weeks * K supplementation would be allowed * Myocardial infarction, heart failure hospitalization, or stroke 8 weeks prior to randomization * If the patient is only on an alpha blocker, as the sole antihypertensive drug, they will be excluded * Pregnant or breastfeeding women or women who are planning to become pregnant or those not using a reliable form of contraception * Known hypersensitivity or a prior documented adverse reaction to CTD or SPL