Educational use only. Drug cards are AI-assisted study material for NCLEX preparation.
Mechanism of action
Inhibits the Na+/Cl⁻ symporter in the distal convoluted tubule, producing modest diuresis and lowering blood pressure with chronic use. First-line for essential hypertension; also used for mild edema and for reducing recurrent calcium-containing kidney stones.
Adverse effects
Life-threatening / NCLEX-tested
- Hypokalemia → cardiac arrhythmias (especially with digoxin)
- Hyponatremia (more common in older adults)
- Hypercalcemia (opposite of loop diuretics)
- Hyperglycemia — can unmask or worsen diabetes
- Hyperuricemia → gout flare
- Sulfa-class allergy cross-reactivity
- Photosensitivity rash
Side effects
Common — what to teach
- Dizziness, lightheadedness
- Increased urination, especially in the first few weeks
- Erectile dysfunction
- Muscle cramps (often hypokalemia)
- Mild dehydration symptoms
Food & drug interactions
With digoxin, thiazide-induced hypokalemia drives toxicity. Lithium clearance falls — risk of lithium toxicity. NSAIDs blunt the antihypertensive effect. Combination with ACE inhibitors or ARBs is common and synergistic, but the combination amplifies first-dose hypotension. Encourage potassium-rich foods unless contraindicated.
Nursing implications
Assessment, monitoring, patient teaching
- Check BP before dosing; teach patients to rise slowly to limit orthostasis
- Monitor K+, Na+, Ca++, glucose, and uric acid at baseline and periodically
- Take in the morning to avoid nocturia
- Counsel about photosensitivity — sunscreen and protective clothing
- Teach signs of hypokalemia (cramps, weakness, palpitations) and high-K+ foods
- Reinforce that BP control is gradual — full effect takes weeks
When to hold / contraindications
- Serum K+ < 3.5 mEq/L
- SBP < 90 mmHg or symptomatic hypotension
- Severe hyponatremia (Na+ < 130) until corrected
- Anuria
- Known sulfa hypersensitivity
Memory anchor
Thiazides "raise the sugars and the calcium, drop the potassium and the sodium" — opposite calcium handling from loop diuretics. Daily morning dose; sunscreen on bright days.
Practice Hydrochlorothiazide questions
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