Classifications: electrolyte & water balance agent; thiazide diuretic; antihypertensive
Pregnancy Category: C
250 mg, 500 mg tablets; 250 mg/5 mL suspension; 500 mg injection
Thiazide diuretic chemically related to sulfonamides. Primary action is production of diuresis by direct action on the distal
convoluted tubules. Inhibits reabsorption of sodium, potassium, and chloride ions. Promotes renal excretion of sodium (and
water), bicarbonate, and potassium; decreases renal calcium excretion and supports uric acid excretion.
Antihypertensive mechanism is unclear but correlates with contraction of extracellular and intravascular fluid volumes and
direct vasodilatory effect on vascular wall. This initially reduces cardiac output with subsequent decrease in peripheral
resistance through autoregulatory mechanisms.
Adjunctively to manage edema associated with CHF, hepatic cirrhosis, renal dysfunction, corticosteroid, or estrogen therapy.
Used alone as step 1 agent in stepped-care approach, or in combination with other agents for treatment of hypertension.
To reduce polyuria of central and nephrogenic diabetes insipidus, to prevent calcium-containing renal stones, and to treat
renal tubular acidosis.
Hypersensitivity to thiazide or sulfonamides; anuria; hypokalemia; pregnancy (category C).
History of sulfa allergy; impaired renal or hepatic function or gout; lactation; hypercalcemia, diabetes mellitus, older adult
or debilitated patients, pancreatitis, sympathectomy, jaundiced children.
Adult: PO 250 mg1 g/d in 12 divided doses IV 250 mg1 g/d in 12 divided doses
Geriatric: PO 500 mg qd or 1 g 3 times/wk
<6 mo: 2040 mg/kg/d in 12 divided doses; >6 mo: 20 mg/kg/d in 2 divided doses IV
<6 mo: 24 mg/kg/d in 2 divided doses; >6 mo: 4 mg/kg/d
- Give with or after food to prevent gastric irritation. Extent of absorption appears to be increased by taking it with food.
- Schedule daily doses to avoid nocturia and interrupted sleep.
- Reserve for emergency or when patient unable to take oral medication. IV administration to infants and children: Verify correct
IV concentration and rate of infusion with physician.
PREPARE: Intermittent: Reconstitute the 500 mg vial with at least 18 mL sterile water for injection. May be further diluted with D5W or NS.
ADMINISTER: Intermittent: Give at a rate of 0.5 gram over 5 min.
- Thiazide preparations are extremely irritating to the tissues, and great care must be taken to avoid extravasation. If infiltration
occurs, stop medication, remove needle, and apply ice if area is small.
Body as a Whole: Fever, respiratory distress, anaphylactic reaction. CV: Irregular heart beat, weak pulse, orthostatic hypotension. GI: Vomiting, acute pancreatitis, diarrhea. Hematologic:
Agranulocytosis (rare), aplastic anemia (rare), asymptomatic hyperuricemia, hyperglycemia, glycosuria, SIADH secretion. Metabolic:
Hypokalemia, hypercalcemia, hyponatremia, hypochloremic alkalosis, elevated cholesterol and triglyceride levels. CNS: Unusual fatigue, dizziness, mental changes, vertigo, headache. Skin: Urticaria, photosensitivity, skin rash.
- Store tablets, PO solutions, and parenteral dosage forms at 15°30° C (59°86° F) unless otherwise
directed by manufacturer. Unused reconstituted IV solutions may be stored at room temperature up to 24 h. Use only clear solutions.
Chlorothiazide (thiazides) may cause: marked increases in serum amylase values, decrease in PBI determinations; increase in excretion of PSP; increase in BSP retention; false-negative phentolamine and tyramine tests; interference with urine steroid determinations, and possibly the histamine test for pheochromocytoma. Thiazides should be discontinued at least 3 d before bentiromide test (thiazides can invalidate test) and before parathyroid function tests because they tend to decrease calcium excretion.
corticosteroids increase hypokalemic effects of chlorothiazide; the hypoglycemic effects of sulfonylureas and insulin may be antagonized; cholestyramine,
colestipol decrease thiazide absorption; intensifies hypoglycemic and hypotensive effects of diazoxide; increased potassium and magnesium loss may cause digoxin toxicity; decreases lithium excretion, increasing its toxicity; increases risk of nsaid-induced renal failure and may attenuate diuresis.
Absorption: Incompletely absorbed PO. Onset: 2 h PO; 15 min IV. Peak: 36 h PO; 30 min IV. Duration: 612 h PO; 2 h IV. Distribution: Distributed throughout extracellular tissue; concentrates in kidney; crosses placenta. Metabolism: Does not appear to be metabolized. Elimination: Excreted in urine and breast milk. Half-Life: 45120 min.
Assessment & Drug Effects
- Monitor for therapeutic effect. Antihypertensive action of a thiazide diuretic requires several days before effects are observed;
usually optimum therapeutic effect is not established for 34 wk.
- Lab tests: Baseline and periodic determinations are indicated for blood count, serum electrolytes, CO2, BUN, creatinine, uric acid, and blood glucose.
- Monitor for hyperglycemia. Thiazide therapy can cause hyperglycemia (see Appendix F) and glycosuria in diabetic and diabetic-prone
individuals. Dosage adjustment of hypoglycemic drugs may be required.
- Monitor patients with gout. Asymptomatic hyperuricemia can be produced because of interference with uric acid excretion.
- Establish baseline weight before initiation of therapy. Weigh patient at the same time each a.m. under standard conditions.
A gain of more than 1 kg (2.2) within 2 or 3 d and a gradual weight gain over the week's period is reportable. Tell patient
to report signs of edema (hands, ankles, pretibial areas).
- Monitor BP closely during early drug therapy.
- Inspect skin and mucous membranes daily for evidence of petechiae in patients receiving large doses and those on prolonged
- Monitor I&O rates and patterns: Excessive diuresis or oliguria may cause electrolyte imbalance and necessitate prompt dosage
- Monitor patients on digitalis therapy for S&S of hypokalemia (see Appendix G). Even moderate reduction in serum potassium
can precipitate digitalis intoxication in these patients.
Patient & Family Education
- Urination will occur in greater amounts and with more frequency than usual, and there will be an unusual sense of tiredness.
With continued therapy, diuretic action decreases; hypotensive effects usually are maintained, and sense of tiredness diminishes.
- If orthostatic hypotension is a troublesome symptom (and it may be, especially in the older adult), consult physician for
measures that will help tolerate the effect and to prevent falling.
- Report to physician any illness accompanied by prolonged vomiting or diarrhea.
- Avoid drinking large quantities of coffee or other caffeine drinks. Caffeine is a CNS stimulant with diuretic effects.
- Report S&S of hypokalemia, hypercalcemia, or hyperglycemia (see Appendix F).
- Hypokalemia may be prevented if the daily diet contains potassium-rich foods. Eat a banana and drink at least 6 oz orange
juice every day. Collaborate with dietitian and physician.
- Report photosensitivity reaction to physician if it occurs. Thiazide-related photosensitivity is considered a photoallergy
(radiation changes drug structure and makes it allergenic for some individuals). It occurs 1 ½2 wk after initial sun
- Do not breast feed while taking this drug without consulting physician.