Renal
Diuretics that regulate fluid volume, electrolytes, and blood pressure by acting at specific points along the nephron. Learn them as a map of the tubule: where each acts sets its potency, its electrolyte fingerprint, and its dangers. (The Cardiovascular section covers diuretics from the heart-failure/blood-pressure angle — this section takes the renal view.) The carbonic anhydrase inhibitors (acetazolamide, methazolamide) and the osmotic diuretic mannitol are used mostly for the eye, altitude sickness and raised intracranial pressure. Tolvaptan, a vasopressin antagonist, blocks the V2 receptor so the kidney excretes free water without salt (aquaresis) — for low sodium (Samsca) and polycystic kidney disease (Jynarque). The potassium binders (sodium polystyrene sulfonate, patiromer, sodium zirconium cyclosilicate) remove potassium through the gut; their onset is delayed, so they are not emergency treatment for life-threatening hyperkalemia. The section also covers the overactive bladder agents — antimuscarinics and β3 agonists that calm the bladder muscle rather than act on the nephron.
Loop Diuretics
-semide High-yieldThe most powerful ("high-ceiling") diuretics — they work even in kidney failure. Watch potassium, volume, and hearing.
Thiazide Diuretics
High-yieldFirst-line for hypertension — a milder diuretic acting further down the nephron. Remember the four metabolic highs — glucose, lipids, uric acid and calcium — and that the calcium rise comes from retention (opposite of loops).
Potassium-Sparing Diuretics
High-yieldWeak diuretics that preserve potassium instead of wasting it — the defining danger is hyperkalemia. Two mechanisms; spironolactone also lowers heart-failure mortality.
Carbonic Anhydrase Inhibitors & Osmotic Diuretics
High-yieldTwo diuretic groups that are used mostly for something other than edema: the carbonic anhydrase inhibitors acetazolamide and methazolamide (glaucoma, altitude sickness) and the osmotic diuretic mannitol (raised intracranial or intraocular pressure). Watch for metabolic acidosis, low potassium and serious sulfonamide reactions with the first group, and for fluid overload, kidney injury and electrolyte swings with mannitol.
Vasopressin Antagonists
-vaptan High-yieldTolvaptan blocks vasopressin’s V2 receptor in the kidney so the body sheds free water and serum sodium rises (Samsca, for hyponatremia), and it slows kidney decline in polycystic kidney disease (Jynarque). The two brands carry different boxed warnings: correcting sodium too fast, and serious liver injury.
Electrolyte & Fluid Replacement
High-yieldReplacing potassium, magnesium, calcium, phosphate & fluids, and correcting acidosis with IV bicarbonate. IV potassium is high-alert — NEVER push it.
Potassium Binders
High-yieldGut-acting drugs that bind potassium in the intestine so it leaves in the stool. Their onset is delayed, so they are not emergency treatment for life-threatening hyperkalemia. Watch for low potassium, the sodium they carry (sodium polystyrene sulfonate, Lokelma), low magnesium (Veltassa) and their effects on other oral drugs.
Overactive Bladder Agents
High-yieldCalm an overactive bladder two ways: antimuscarinics (tolterodine, solifenacin, darifenacin, trospium, fesoterodine) block the detrusor’s muscarinic receptors, and β3 agonists (mirabegron, vibegron) relax it while it fills. Watch for urinary retention, angioedema and — with antimuscarinics — confusion in older adults.