Thiazides- medium efficacy diuretics with primary site of action in the early DT (Site III). Here they inhibit Na+-Ct sympo at the luminal membrane. Under their action, an increased amount of Na is presented to the distal nephron, more of it is exchanges with K+, urinary K+ excretion increased in parallel to the natriuretic response. They decrease renal Ca excretion and increase Mg excretion by a direct distal tubular action. They also decrease urate excretion by the same mechanism as furosemide. They are used in idiopathic hypercalciuria REF Essentials of Medical Pharmacology, K.D Tripathi,6 th edition, page 564