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Drug dosage identifier


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This is NOT hydrochlorothiazide. Check doses carefully.

From July 2013, NICU has changed from using hydrochlorothiazide to chlorothiazide to bring us in line with Pharmac requirements and the remainder of Starship. Hydrochlorothiazide is no longer available anywhere in ADHB. Dosages are 10-fold different between these two drugs - please double check doses carefully.

Dose and administration

10-20 mg/kg/dose 12-hourly PO.


  • Control of pulmonary oedema in preterm infants with chronic lung disease.
  • Diuretic for long term control of mild to moderate oedema associated with congestive heart failure (generally in combination with spironolactone).


  • Known hypersensitivity to thiazides or sulphonamide derivatives.
  • Anuria.
  • Severe renal or hepatic dysfunction


  • Decreased renal or hepatic function.
  • Electrolyte imbalances.
    • Chlorothiazide causes increased urinary losses of sodium, chloride, potassium, bicarbonate, magnesium and phosphate
    • Chlorothiazide decreases renal excretion of calcium
  • Neonates with significant jaundice (chlorothiazide competes with bilirubin for available plasma albumin-binding sites).

Clinical pharmacology

Chlorothiazide is a thiazide diuretic - a moderately potent diuretic which acts at the proximal end of the distal tubule to cause a decrease in reabsorption of electrolytes and an increase in excretion of sodium and chloride ions with accompanying water loss.

For further information see Reference Viewer.

Possible adverse effects

  • Gastrointestinal disturbance (nausea, vomiting, diarrhoea)
  • Hypokalaemia, hypochloraemic alkalosis, hypomagnesaemia, hypophosphotaemia, hyponatraemia.
  • Hypercalcaemia, hyperglycaemia, hyperuricaemia.
  • Altered plasma-lipid concentrations
  • Hypersensitivity reactions (skin reactions, photosensitivity, fever, respiratory distress, blood dyscrasias).
  • Possibly kernicterus in very jaundiced babies.

Special considerations

  • Monitor sodium, potassium, calcium and glucose levels.
  • Effects appear increased when used in combination with furosemide or spironolactone. Combined use with spironolactone, however, causes urinary calcium loss of a magnitude similar to that caused by furosemide, possibly resulting in bone demineralization in the pre-term infant.
  • Distal diuretics (eg. chlorothiazide) improve pulmonary mechanics in preterm infants, aged greater than 3 weeks, with chronic lung disease. The use of distal diuretics reduces the need for furosemide .
  • Chronic administration can lead to significant urinary losses of magnesium that can precipitate symptoms of magnesium deficiency.
  • NSAIDs decrease antihypertensive response.
  • Digoxin: increased risk of digitalis toxicity from thiazide-induced hypokalaemia.
  • Diazoxide: increased antihypertensive, hyperglycaemic or hyperuricaemic effects.

Management of Chlorothiazide administration


Chlorothiazide is charted on the prescription chart in mg/dose.


Administer with or after feeds to prevent gastrointestinal upset, and enhance absorption.

Nursing considerations

  • Monitor renal function, daily B.P. and record fluid intake and output.
  • Measure serum electrolytes and blood glucose when indicated.


Follow instructions on the bottle label.


  1. Northern Neonatal Network. Neonatal Formulary. 6th edition. Chichester: Wiley-Blackwell; 2011.
  2. Young BM, Mangum B. Neofax. 18th edition. Raleigh: Acorn Publishing; 2005
  3. Khanderia S, Managing Editor. BNF for Children May 2013. London: BMJ Group, Pharmaceutical Press and RCPCH Publications Ltd; 2013

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Document Control

  • Date last published: 29 May 2013
  • Document type: Drug Dosage Guideline
  • Services responsible: ADHB Pharmacy, Neonatology
  • Editor: Sarah Bellhouse
  • Review frequency: 2 years