Adverse Effects and Drug Interactions

General Diuretic AEs - Fluid & Lytes Gone Wild

• Hemodynamic:
  • Hypovolemia → ↓ perfusion, azotemia.
  • Hypotension (orthostatic), dizziness.
• Electrolyte Disturbances:
  • Hyponatremia (↓Na⁺): Common with thiazides in elderly.
  • Hypokalemia (↓K⁺): Weakness, arrhythmias (Loops, Thiazides).
  • Hyperkalemia (↑K⁺): K⁺-sparing diuretics, ACEIs.
  • Hypomagnesemia (↓Mg²⁺): Tetany, arrhythmias (Loops, Thiazides).
  • Calcium: ↓Ca²⁺ (Loops); ↑Ca²⁺ (Thiazides).
• Acid-Base Imbalances:
  • Metabolic Alkalosis (Loops & Thiazides).
  • Metabolic Acidosis (CAIs, K⁺-sparing).
• Metabolic & Other:
  • Hyperuricemia → Gout (Thiazides > Loops).
  • Hyperglycemia, glucose intolerance (Thiazides, Loops).
  • Dyslipidemia: ↑LDL, ↑TG (Thiazides).
  • Ototoxicity (IV Loops).

⭐ Diuretic-induced hyponatremia is particularly common and concerning in elderly patients taking thiazides; can cause confusion/seizures.

Loop & Thiazide AEs - Ouch, Sugar, Gout!

⭐ Ethacrynic acid, a loop diuretic, is an option for patients with sulfa allergy but carries a higher risk of ototoxicity.

Key Interactions:

• NSAIDs: ↓ diuretic effect.
• Aminoglycosides (with Loops): ↑ ototoxicity.
• Digoxin: ↑ toxicity if hypokalemia.
• Lithium: ↓ clearance, ↑ toxicity (especially Thiazides).

K-Sparing & Other AEs - HyperK & Odd Jobs

• K-Sparing Diuretics:
  • Hyperkalemia (Serum K+ > 5.5 mEq/L): Most significant; risk ↑ with ACEi/ARBs, NSAIDs, renal insufficiency.
  • Spironolactone:
    • Antiandrogenic effects: Gynecomastia (can be painful), menstrual irregularities, impotence.

    ⭐ Spironolactone-induced painful gynecomastia is a common reason for non-compliance.

  • Amiloride & Triamterene:
    • Metabolic acidosis (Type 4 RTA-like, due to ↓ H+ secretion).
    • Triamterene: Blue fluorescence in urine, nephrolithiasis (poorly soluble), megaloblastic anemia (folate antagonist).
• Osmotic Diuretics (e.g., Mannitol):
  • Initial: ECF volume expansion (⚠️ can precipitate pulmonary edema in HF patients).
  • Later: Dehydration, electrolyte imbalances (hypernatremia, hyponatremia, hypokalemia).
  • Headache, nausea, vomiting.
• Carbonic Anhydrase Inhibitors (CAIs - e.g., Acetazolamide):
  • Metabolic acidosis (non-anion gap, due to renal HCO₃⁻ wasting).
  • Hypokalemia (due to ↑ K+ secretion in distal nephron).
  • Renal stones (calcium phosphate, from ↑ urinary pH & ↑ phosphate excretion).
  • Paresthesias, drowsiness, tinnitus.
  • Sulfa allergy (cross-reactivity).

Diuretic Drug Interactions - Risky Mixes

Key interactions to monitor for enhanced toxicity or reduced efficacy:

High‑Yield Points - ⚡ Biggest Takeaways

• Loop and Thiazide diuretics commonly cause hypokalemia and metabolic alkalosis.
• Potassium-sparing diuretics can lead to hyperkalemia, especially with ACE inhibitors or ARBs.
• Loop diuretics (e.g., furosemide) carry a risk of ototoxicity, worsened by aminoglycosides.
• Thiazides are associated with hyperuricemia, hyperglycemia, and hyperlipidemia.
• NSAIDs can reduce the efficacy of most diuretics.
• Lithium toxicity risk is increased with thiazides and loop diuretics.
• Spironolactone may cause gynecomastia and other anti-androgenic effects.