HYDROCHLOROTHIAZIDE

(hye-droe-klor-oh-thye'a-zide)

Apo-Hydro

, Esidrix, Oretic, HCTZ, Urozide

Classifications: electrolytic and water balance agent; diuretic; thiazide;
Therapeutic: diuretic
Pregnancy Category: B

Availability

12.5 mg capsules; 25 mg, 50 mg, 100 mg tablets; 50 mg/5 mL oral solution

Action

Diuretic action is associated with drug interference with absorption of sodium ions across the distal renal tubular segment of the nephron. This enhances excretion of sodium, chloride, potassium, bicarbonates, and water.

Therapeutic Effect

It has hypotensive action, elevates plasma renin activity.

Uses

Adjunct in treatment of edema associated with CHF, hepatic cirrhosis, renal failure, and in the management of hypertension.

Unlabeled Uses

Nephrogenic diabetes insipidus, hypercalciuria, and treatment of electrolyte disturbances associated with renal tubular acidosis.

Contraindications

Hypersensitivity to thiazides or other sulfonamides; anuria.

Cautious Use

Bronchial asthma, allergy; hepatic cirrhosis; renal dysfunction; CHF; stroke, CVA; history of gout, SLE; diabetes mellitus; older adults; pregnancy (category B).

Route & Dosage

Edema
Adult: PO 25–200 mg/d in 1–3 divided doses

Hypertension
Adult: PO 12.5–100 mg/d in 1–2 divided doses
Child: PO 2.2 mg/kg/d in 2 divided doses
Neonate (<6 mo): PO 2–4 mg/kg/d in 2 divided doses

Administration

Oral

Give with food or milk to reduce GI upset.
Schedule doses to avoid nocturia and interrupted sleep. If given in 2 doses, schedule second dose no later than 3 p.m.
Store tablets in tightly closed container at 15°–30° C (59°–86° F) unless otherwise directed.

Adverse Effects (≥1%)

CNS: Mood changes, unusual tiredness or weakness, dizziness, light-headedness, paresthesias. CV: Irregular heartbeat, weak pulse, orthostatic hypotension. GI: Dry mouth, increased thirst, nausea, vomiting, anorexia, diarrhea, pancreatitis, jaundice. Hematologic: Agranulocytosis, thrombocytopenia, aplastic anemia, leukopenia. Metabolic: Hyperglycemia, glycosuria, hyperuricemia, hypokalemia. Other: Hypersensitivity reactions, photosensitivity, blurred vision, yellow vision (xanthopsia), muscle spasm.

Diagnostic Test Interference

Falsely decreased value in total-urinary estrogen by spectrophotometric assay. See chlorothiazide.

Interactions

Drug: Amphotericin B, corticosteroids increase hypokalemic effects; sulfonylureas, insulin may antagonize hypoglycemic effects; cholestyramine, colestipol decrease thiazide absorption; diazoxide intensifies hypoglycemic and hypotensive effects; increased potassium and magnesium loss may cause digoxin toxicity; decreases lithium excretion and increases toxicity; increases risk of nsaid-induced renal failure and may attenuate diuresis.

Pharmacokinetics

Absorption: Incompletely absorbed. Onset: 2 h. Peak: 4 h. Duration: 6–12 h. Distribution: Distributed throughout extracellular tissue; concentrates in kidney; crosses placenta; distributed in breast milk. Metabolism: Does not appear to be metabolized. Elimination: In urine. Half-Life: 45–120 min.

Nursing Implications

Assessment & Drug Effects

Monitor for therapeutic effectiveness. Antihypertensive effects may be noted in 3–4 d; maximal effects may require 3–4 wk.
Lab tests: Baseline and periodic determinations of serum electrolytes, blood counts, BUN, blood glucose, uric acid, CO₂, are recommended.
Check BP before initiation of therapy and at regular intervals.
Monitor closely for hypokalemia; it increases the risk of digoxin toxicity.
Monitor I&O and check for edema.
Note: Drug may cause hyperglycemia and loss of glycemic control in diabetics.
Note: Drug may cause orthostatic hypotension, dizziness.

Patient & Family Education

Consult physician before using OTC drugs. Many contain large amounts of sodium as well as potassium.
Monitor weight daily.
Note: Diabetic patients need to monitor blood glucose closely. This drug causes impaired glucose tolerance.
Report signs of hypokalemia (see Appendix F) to physician.
Change positions slowly; avoid hot baths or showers, extended exposure to sunlight, and sitting or standing still for long periods.
Note: Photosensitivity reaction may occur 10–14 d after initial sun exposure.

Common adverse effects in italic, life-threatening effects underlined; generic names in bold; classifications in SMALL CAPS; Canadian drug name; Prototype drug

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