Classifications: electrolyte & water balance agent; thiazide diuretic; antihypertensive; Therapeutic: thiazide diuretic; antihypertensive
Pregnancy Category: C
250 mg, 500 mg tablets; 500 mg injection
Thiazide diuretic whose 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.
Antihypertensive mechanism is due to decreased peripheral resistance and reduced blood pressure.
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; renal failure; jaundiced neonates; SLE; pregnancy (category
History of sulfa allergy; impaired renal or hepatic function or gout; hypercalcemia, diabetes mellitus, older adult or debilitated
patients, pancreatitis, sympathectomy.
Route & Dosage
Adult: PO 250 mg1 g/d in 12 divided doses IV 500 mg1 g/d in 12 divided doses
Geriatric: PO 500 mg qd or 1 g 3 times/wk
Child: PO <6 mo, 2040 mg/kg/d in 12 divided doses; >6 mo, 20 mg/kg/d in 2 divided doses
- 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 g over 5 min.
INCOMPATIBILITIES Solution/additive: Amikacin, chlorpromazine, codeine, fluorouracil, hydralazine, insulin, levorphanol, methadone, morphine, norepinephrine, pentobarbital, polymyxin B, procaine, prochlorperazine, promazine, promethazine, streptomycin, triflupromazine, vancomycin, vitamin B complex with C, warfarin.
- 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.
- 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
Adverse Effects (≥1%) Body as a Whole:
Fever, respiratory distress, anaphylactic reaction. CV:
Irregular heart beat, weak pulse, orthostatic hypotension. GI:
Vomiting, acute pancreatitis
. Hematologic: Agranulocytosis
(rare), aplastic anemia
hyperuricemia, hyperglycemia, glycosuria, SIADH secretion. Metabolic: Hypokalemia,
hypercalcemia, hyponatremia, hypochloremic alkalosis, elevated cholesterol and triglyceride levels. CNS:
, dizziness, mental changes, vertigo, headache. Skin:
Urticaria, photosensitivity, skin rash.
Diagnostic Test Interference
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.
InteractionsDrug: Amphotericin B, corticosteroids
increase hypokalemic effects of chlorothiazide; the hypoglycemic effects of sulfonylureas
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
failure and may attenuate diuresis.
Incompletely absorbed PO. Onset:
2 h PO; 15 min IV
36 h PO; 30 min IV
612 h PO; 2 h IV
Throughout extracellular tissue
; concentrates in kidney; crosses placenta. Metabolism:
Does not appear to be metabolized. Elimination:
In urine and breast milk. Half-Life:
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?2 wk after initial sun