Diachlor, SK-Chlorothiazide
Sodium Diuril
Classifications: electrolyte & water balance agent; thiazide diuretic; antihypertensive
Prototype: Hydrochlorothiazide
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.

Therapeutic Effects

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.

Unlabeled Uses

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).

Cautious Use

History of sulfa allergy; impaired renal or hepatic function or gout; lactation; hypercalcemia, diabetes mellitus, older adult or debilitated patients, pancreatitis, sympathectomy, jaundiced children.

Route & Dosage

Hypertension, Edema
Adult: PO 250 mg–1 g/d in 1–2 divided doses IV 250 mg–1 g/d in 1–2 divided doses
Geriatric: PO 500 mg qd or 1 g 3 times/wk

Child: PO <6 mo: 20–40 mg/kg/d in 1–2 divided doses; >6 mo: 20 mg/kg/d in 2 divided doses IV <6 mo: 2–4 mg/kg/d in 2 divided doses; >6 mo: 4 mg/kg/d


  • 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.  

INCOMPATIBILITIES Solution/additive: Amikacin, chlorpromazine, hydralazine, insulin, levorphanol, morphine, norepinephrine, polymyxin B, procaine, prochlorperazine, promazine, promethazine, streptomycin, triflupromazine, vancomycin.

  • 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.

Adverse Effects (1%)

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.

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.


Drug: Amphotericin B, 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: 3–6 h PO; 30 min IV. Duration: 6–12 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: 45–120 min.

Nursing Implications

Assessment & Drug Effects

Patient & Family Education

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