Diuretics and Other Cardiac Drugs
Diuretics, antiarrhythmics, nitrates and vasoactive infusions
Diuretics
| Type | Examples | Key points |
|---|---|---|
| Loop | furosemide, bumetanide, torsemide | Act on the thick ascending loop of Henle; most potent. ↓ K⁺, ↓ Mg²⁺, ↓ Na⁺, dehydration, hypotension, ↑ glucose and uric acid. Ototoxicity with rapid IV push or high doses: give IV slowly. Low K⁺ raises digoxin toxicity. |
| Thiazide | hydrochlorothiazide, chlorthalidone, metolazone | Act on the distal convoluted tubule. ↓ K⁺, ↓ Na⁺, ↑ Ca²⁺, ↑ glucose, ↑ uric acid, photosensitivity. Raise lithium levels. |
| Potassium-sparing | spironolactone, eplerenone, amiloride, triamterene | ↑ K⁺: no potassium supplements or salt substitutes; caution with ACEi/ARB. Spironolactone: gynecomastia, menstrual changes. |
| Osmotic | mannitol | ↓ intracranial and intraocular pressure. Use an in-line filter (crystals). Watch for fluid overload and pulmonary edema, electrolytes, osmolality. |
| Carbonic anhydrase inhibitor | acetazolamide | Glaucoma, altitude sickness. Metabolic acidosis, low K⁺, tingling. |
All diuretics: give in the morning (avoid nocturia), daily weight, I&O, BP, electrolytes. Sulfa allergy is not a reliable reason to avoid loop or thiazide diuretics (cross-reactivity is not supported). Updated
Amiodarone
For VT/VF and atrial fibrillation. Long half-life (weeks to months).
- Lungs: pulmonary toxicity (cough, dyspnea): baseline chest X-ray and lung tests.
- Thyroid: hypo- or hyperthyroidism (it contains iodine): check TSH.
- Liver tests; eyes (corneal deposits, optic neuropathy); skin (photosensitivity, blue-gray color).
- Bradycardia, QT prolongation; IV can cause hypotension.
- Raises warfarin and digoxin levels: doses need lowering.
Nitrates
- Sublingual tablet or spray: 1 dose every 5 min, max 3; call emergency services if pain isn't better 5 min after the first dose.
- Store tablets in the original dark glass bottle.
- Patch/ointment: rotate sites, remove the old one, wear gloves; plan a nitrate-free period (usually 10–12 h overnight) to prevent tolerance.
- Headache (expected; acetaminophen), hypotension, dizziness.
- Never with PDE-5 inhibitors (sildenafil, vardenafil within 24 h; tadalafil within 48 h).
Vasoactive infusions (ICU)
| Norepinephrine | First-line in septic shock. Vasoconstrictor. Extravasation → tissue necrosis: stop, leave the catheter, give phentolamine per protocol |
| Epinephrine | Anaphylaxis (IM 0.3–0.5 mg of 1 mg/mL in adults), cardiac arrest, shock |
| Vasopressin | Added to norepinephrine in septic shock |
| Dobutamine | Inotrope (↑ contractility) for cardiogenic shock and HF; can cause tachycardia, dysrhythmias |
| Dopamine | Bradycardia or shock (second-line); dose-dependent effects |
Use a central line when possible, an infusion pump, and frequent BP (often an arterial line). Typical target: MAP ≥65 mmHg.
Priority
Before digoxin: apical pulse 1 full minute (hold if <60 in adults) and check K⁺. Before a beta blocker or diltiazem: HR and BP. Before a diuretic: K⁺ and BP. Assess first, then give.