Hydrochlorothiazide

Benjamin Clanner-Engelshofen is a freelance writer in the medical department. He studied biochemistry and pharmacy in Munich and Cambridge / Boston (USA) and noticed early on that he particularly enjoyed the interface between medicine and science. That is why he went on to study human medicine.

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The active ingredient hydrochlorothiazide is a water tablets (diuretic) belonging to the class of thiazide diuretics. The increased excretion of water lowers the blood pressure, the cardiovascular system is relieved and water accumulations in the tissue (edema) are flushed out. Read more about hydrochlorothiazide here: effect, application, side effects and interactions.

This is how hydrochlorothiazide works

Hydrochlorothiazide works directly in the kidneys. There the entire volume of blood is passed through about three hundred times per day. The so-called primary urine is pressed out through a filter system, the kidney corpuscles. This primary urine still contains the same concentration of salts and small molecules (such as sugar and amino acids) as the blood. The primary urine is then transported via the kidney tubules, where it is concentrated to secondary or terminal urine, into the renal pelvis, the ureters and finally into the bladder. In the kidney tubules, water and energy-rich substances (salts, sugar, amino acids) that can still be used by the body are reabsorbed. The 180 liters of primary urine produced per day in an adult result in around two liters of terminal urine, i.e. urine.

In the kidney tubules, hydrochlorothiazide blocks proteins in the cells that line the tubules. These proteins absorb sodium and chloride, i.e. table salt, back into the body. This re-absorption also means that water is “drawn in” into the body, i.e. less is excreted. By blocking these transporter proteins, an increased "diuresis" (excretion of water) takes place.

The increased excretion of water also effectively decreases the blood volume and the amount of water that has accumulated in the tissue. This lowers blood pressure, which means that the heart has to work less intensively. This relieves the heart and the vessels near the heart.

Ingestion, breakdown and excretion of hydrochlorothiazide

After ingestion, the active ingredient hydrochlorothiazide is largely absorbed from the intestine into the blood and about 75 percent is found there after two to five hours. It develops its effect in the kidney tubules, which is noticeable about one to two hours after ingestion. Finally, the active ingredient is excreted in the urine via the kidneys. About six to eight hours after ingestion, half of the active ingredient has left the body.

When is hydrochlorothiazide used?

The diuretic hydrochlorothiazide is used for:

• High blood pressure (arterial hypertension)
• Water retention in the tissue (edema)

Hydrochlorothiazide is often administered in combination with other active ingredients that are supposed to have an even more targeted effect on the underlying disease (for example, in heart failure together with ACE inhibitors).

In the case of chronic underlying diseases, the diuretic can be used long-term.

This is how hydrochlorothiazide is used

Hydrochlorothiazide is usually taken in the form of tablets, whole with a glass of water to eat. It is usually taken once a day in the morning. In the case of very high doses of hydrochlorothiazide, however, it may be appropriate to split the total amount into two doses (intake in the morning and in the early evening).

A higher dose can be prescribed at the beginning of therapy; the maintenance dose for high blood pressure is usually 12.5 milligrams of hydrochlorothiazide. Very high doses of up to a hundred milligrams of hydrochlorothiazide per day can be prescribed, especially when flushing out edema.

If it is a combined dosage form with additionally contained active ingredients, the dosage instructions may differ.

What are the side effects of hydrochlorothiazide?

More than one in ten patients experience side effects due to the high loss of water and electrolytes. Examples are too low sodium, potassium, magnesium and chloride values ​​(hyponatremia, hypokalaemia, hypomagnesaemia, hypochloremia), increased blood lipid values ​​and increased calcium values ​​(hypercalcaemia).

Hydrochlorothiazide side effects such as excessively high uric acid levels (hyperuricemia, which can lead to gout attacks in gout patients), excessively high blood sugar levels (hyperglycaemia), skin rash with itching, loss of appetite, nausea, vomiting, erectile dysfunction, are common (in one in ten to one hundred people treated) Drop in blood pressure when getting up from a sitting or lying position (orthostatic hypotension) - especially at the beginning of therapy with hydrochlorothiazide.

What should be considered when taking hydrochlorothiazide?

The lowering of blood pressure caused by hydrochlorothiazide can be increased excessively by concomitant use with other active substances. These include in particular other diuretics, cardiovascular drugs such as beta blockers, ACE inhibitors (captopril, enalapril) and nitrates (against angina pectoris), as well as sleeping pills from the group of barbiturates, tricyclic antidepressants, other vasodilators and alcohol.

Non-steroidal anti-inflammatory drugs (NSAIDs) that are often taken as pain relievers (such as acetylsalicylic acid / ASA, ibuprofen, naproxen, diclofenac) can weaken the effect of hydrochlorothiazide.

Caution is advised when simultaneously using active ingredients with a narrow therapeutic range - i.e. active ingredients whose dosage must be adhered to precisely because overdosing or underdosing can quickly occur. Such active ingredients include cardiac glycosides such as digitoxin and digoxin and mood stabilizers such as lithium. When combined with hydrochlorothiazide, blood level controls are recommended.

Diabetics should check their blood sugar levels regularly while taking hydrochlorothiazide.

Since hydrochlorothiazide can lead to an insufficient supply of the placenta and thus the child in pregnant women, it should not be used during pregnancy.

The active ingredient passes into breast milk in small amounts, which is why breastfeeding women should stop breastfeeding if necessary.

Hydrochlorothiazide is not approved for children and adolescents.

Diuretics such as hydrochlorothiazide are not recommended for severe renal impairment, but can be used for mild or moderate renal impairment.

How to get medication containing hydrochlorothiazide

Medicines with the active ingredient hydrochlorothiazide require a prescription and pharmacy in every dosage, pack size and combination.

How long has hydrochlorothiazide been known?

The diuretic hydrochlorothiazide was developed in 1955 by the chemist George deStevens at the pharmaceutical company Ciba-Geigy and marketed as early as 1958. It was one of the first active ingredients that could effectively and reliably lower blood pressure. Numerous combination drugs and generics with the active ingredient hydrochlorothiazide are now available.

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