Hydrochlorothiazide

Hydrochlorothiazide is a diuretic drug and is considered the prototype of the thiazide diuretics. The active ingredient is used, among other things, to treat edema.

What is hydrochlorothiazide?

Hydrochlorothiazide is a diuretic. Diuretics are drugs with a fairly wide therapeutic range. They are mainly used to flush water out of the human body. A distinction can be made between different types of diuretic drugs. Thiazide diuretics, along with the potassium-sparing diuretics and aldosterone antagonists, are among the best-known diuretics.

Thiazide diuretics such as hydrochlorothiazide have a wide range of uses. They are used, among other things, to treat high blood pressure or to treat heart failure. Thiazide diuretics are usually well tolerated, but due to their flushing effect, they can also cause electrolyte disturbances.

Hydrochlorothiazide has been banned for athletes by the World Anti-Doping Agency. Although the drug does not directly increase performance, it is one of the so-called masking agents. These can make the detection of doping substances more difficult. Hydrochlorothiazide dilutes the urine so much that a doping control in the urine is hardly possible.

Pharmacological effect

Hydrochlorothiazide acts on the distal tubules of the nephron. The nephron is the kidney's smallest functional unit. It consists of a kidney corpuscle and a system of tubes connected to it, the so-called tubular system. The primary urine is filtered in the nephron. In the tubule system, water and various other substances are recovered before the so-called secondary urine is excreted via the urinary tract.

Hydrochlorothiazide inhibits the sodium chloride cotransporter on the luminal membrane of the cells in the tubular system. In higher doses, the drug also inhibits carbonic anhydrase. As a result, the kidneys excrete more sodium chloride and thus water. In addition, fewer calcium ions and more magnesium ions are excreted. Hydrochlorothiazide can therefore also lead to increased bone density in patients with osteoporosis due to the increased calcium retention.

The bioavailability of hydrochlorothiazide is 70 percent. The duration of action is 6 to 12 hours. The active ingredient is then excreted through the kidneys almost unchanged.

Medical application & use

Hydrochlorothiazide is mainly used to treat essential arterial hypertension. However, the active ingredient is rarely administered alone. Therapy usually takes place in combination with beta blockers or ACE inhibitors.

Hydrochlorothiazide is also used in heart failure. Here the drug is mostly used in combination with loop diuretics. These serve to mobilize edema, whereas hydrochlorothiazide serves to excrete water. Since hydrochlorothiazide increases the retention of calcium ions, it is also used in the treatment of osteoporosis. The recovered calcium can increase the patient's bone density.

Another indication for the use of hydrochlorothiazide is hypercalciuria. This is an increased excretion of calcium in the urine. Bone metastases, vitamin D intoxication, sarcoid or Bartter syndrome are possible causes of such hypercalciuria. Since urinary stones can occur due to the increased calcium excretion, hydrochlorothiazide is used prophylactically in these cases.

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Risks & side effects

Hydrochlorothiazide is basically well tolerated, but various side effects can develop due to the loss of electrolytes. Often there is a decreased level of potassium and sodium in the blood. Magnesium and chloride are also reduced. In contrast, the calcium level in the blood is increased. Dry mouth and thirst are typical side effects.

At higher doses, weakness, dizziness, muscle pain and muscle cramps may also occur. The patients suffer from palpitations and decreased blood pressure. Especially when changing from lying down to standing, they show orthostatic regulation disorders with dizziness.

At high doses, urine output can be very excessive. As a result of dehydration and hypovolemia, i.e. the reduced amount of blood circulating, the blood thickens. This increases the risk of developing thrombosis or embolism, particularly in older patients or in patients with venous diseases. As a result of hypokalaemia, tiredness, abnormal sleepiness, paralysis or paralysis may occur. Constipation and gas are common side effects of hydrochlorothiazide.

During treatment, increased uric acid levels may occur in the blood, which ultimately lead to gout attacks. An increase in blood lipids (triglycerides and cholesterol) is also often observed. Occasionally, the urinary substances creatinine and urea in the blood also rise.

A dreaded side effect of therapy with hydrochlorothiazide is pancreatitis. Inflammation of the pancreas can be life threatening. Rarely, allergic skin reactions such as itching, rashes or wheals occur when taking hydrochlorothiazide. Acute kidney inflammation, vascular inflammation and anemia are also rare side effects. Some patients may also develop erectile dysfunction or visual disturbances while taking hydrochlorothiazide.

Thiazide diuretics such as hydrochlorothiazide must not be used in severe kidney and liver problems. Severe electrolyte imbalances such as hypokalaemia, hyponatraemia and hypercalcemia are also contraindications. The use of hydrochlorothiazide is dangerous in cases of digitalis intoxication and cardiac arrhythmias. Likewise, hydrochlorothiazide must not be used if you are allergic to sulfonamides. Ideally, the doctor should also prescribe a different diuretic during pregnancy and breastfeeding.