Screening & Evaluation of Diuretics

Introduction & scope

• Diuretic — an agent that increases the rate of urine formation, raising net renal excretion of water and (usually) solute; screening detects this activity in a test compound, evaluation quantifies its potency, electrolyte profile, onset, duration and ceiling.
• Screening (qualitative/quantitative) — does compound X have diuretic activity, and how strong? — a first-pass, high-throughput in-vivo rodent assay (the Lipschitz test) backed by an in-vitro mechanistic assay (carbonic-anhydrase inhibition).
• Evaluation (characterising) — what is the electrolyte signature, onset, peak, duration and site of action? — answered by the saluretic-index rat assay and the catheterised-dog assay.
• Both water and salt matter — diuretics are central to oedema of CHF, ascites and hypertension; a good screen measures both the aquaretic (water) and saluretic (electrolyte) components, since useful diuretics act mainly through natriuresis with secondary water loss.
• Distinct from clinical diuretic pharmacology — this is the bench/preclinical screening-method question — how a novel candidate is tested in enzyme, rat, dog and healthy-volunteer systems, not the clinical use of furosemide/thiazides in patients.
• Positive controls (validity anchor) — every cascade is run with reference diuretics of known class so discriminating power is verifiable — furosemide/bumetanide/piretanide (loop), hydrochlorothiazide (thiazide), acetazolamide (CA inhibitor), amiloride/triamterene (K⁺-sparing), spironolactone (aldosterone antagonist).