Thiazide Diuretics

Thiazide diuretics are a type of fluid tablet that has been widely used for fluid problems since the 1950s. They increase the rate at which the kidney produces urine, and therefore the frequency with which a person has to visit the toilet to pass urine. They include medications such as:

  • hydrochlorothiazide,
  • bendrofluazide,
  • bendrothiazide,
  • benzthiazide,
  • chlorthiazide,
  • chlorthalidone,
  • clopamide,
  • cyclopenthiazide,
  • diazoxide,
  • hydroflumethiazide,
  • metolazone,
  • triamterene,
  • xipamide.

They are used to treat conditions such as high blood pressure, tissue swelling and excess fluid in the body.

They should not be used in pregnancy unless medically essential, and may reduce the volume of milk in breastfeeding. They are sometimes used for this purpose in women who wish to stop breastfeeding. Use thiazides with caution in gout, kidney disease, liver disease, diabetes, SLE and asthma, and not at all if suffering from complete kidney failure.

Common side effects include increased urinary frequency, while unusual ones may include nausea, vomiting, gut cramps, diarrhoea, dizziness, headache and a rash. Uncommonly, photodermatitis (excessively sun sensitive skin) may develop. They may interact with lithium, barbiturates, digoxin, insulin, steroids, lithium, NSAIDs and tablets for controlling maturity onset diabetes. There is a beneficial interaction with most medications that lower blood pressure. The herbs guarana, liquorice, celery, dandelion and uva ursi may also interact with thiazides.

They are not permitted in high-level competitive sports as they act as masking agents for other illegal drugs.

An overdose may cause confusion, dizziness and gut spasms due to chemical (electrolyte) imbalances. Administer activated charcoal or induce vomiting if tablets taken recently, give extra fluids and seek medical assistance.

The chemical structures of some types of thiazide diuretics including hydrochlorothiazid, chlortalidon, clopamid, indapamid, metolazon, zipamid, mefrusid, trichlormethiazid, bendroflumethiazid

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