Hydrochlorothiazide
thiazide diuretic · antihypertensive
Third-party optionBy the Layer Nutrition editorial team · How the atlas classifies the 664 molecules
What this medicine is for
Hydrochlorothiazide is a medicine in the 'thiazide diuretic (antihypertensive)' category. Diuretics help the kidneys eliminate water and salt, which lowers blood pressure and relieves oedema.
In the case of Hydrochlorothiazide, this means: Increases the elimination of water and salt by the kidneys and lowers blood pressure. It is generally taken over the long term, within regular monitoring, and is not stopped on your own initiative.
Under which brands it is found
Hydrochlorothiazide is found in around 113 presentations listed in France. It can be found under several brand names and as generics.
- Alteisduo
- Amiloride Hydrochlorothiazide Teva
- Benazepril Hydrochlorothiazide Eg
- Bisoprolol/Hydrochlorothiazide Arrow Lab
- Bisoprolol/Hydrochlorothiazide Biogaran
- Bisoprolol/Hydrochlorothiazide Cristers
- Bisoprolol/Hydrochlorothiazide Sandoz
- Bisoprolol/Hydrochlorothiazide Teva
- and other presentations
Original brand-name products and generics deliver the same active substance; the choice between them is made with your doctor or pharmacist.
On the plate: potassium and magnesium
On hydrochlorothiazide, the kidney eliminates more potassium and magnesium through the urine. Diet is the first lever for rebuilding these two minerals, and the easiest one to keep up day after day.
Potassium is concentrated in vegetables and fruit: potato, sweet potato, spinach, lentils, beans, avocado, dried apricot, and banana. Magnesium comes mainly from green leafy vegetables, nuts such as almonds and walnuts, pumpkin seeds, whole grains, and dark chocolate.
Several of these foods provide both at once: spinach, lentils, beans, pumpkin seeds. Spreading them across your meals covers a good share of your needs, on top of your treatment. Orange juice and dried fruit such as raisins and prunes easily round out the potassium intake.
How hydrochlorothiazide works
Hydrochlorothiazide belongs to the family of thiazide diuretics. It acts on the kidney, at the level of the distal convoluted tubule, where it selectively inhibits the sodium-chloride cotransporter known as NCC. This transporter is the main entry point for sodium on the apical membrane of the cells in that region. By blocking it, the drug prevents the reabsorption of sodium at this part of the nephron.
When sodium is no longer reabsorbed, it passes into the urine, carrying chloride and water along with it. Diuresis increases, the circulating blood volume falls, and blood pressure drops. The pharmacological effect begins about 2 hours after the dose, reaches its peak around 4 hours, and lasts from 6 to 12 hours. The elimination half-life of the drug ranges from about 5.6 to 15 hours.
Why it is prescribed
The main indication is essential arterial hypertension, which the drug treats alone or in combination with other antihypertensive agents. By lowering the blood volume and then relaxing the resistance of the vessels, it brings blood pressure back toward lower values. This is one of the reasons for its long-standing place in the maintenance treatment of hypertension.
It is also used to reduce edema, these accumulations of water and salt in the tissues, related to heart failure, to the use of corticosteroids, to a nephrotic syndrome, or to estrogen therapy. The drug is contraindicated in cases of anuria, that is to say an absence of urine production, and in cases of known hypersensitivity to the product.
How to take it day to day
It is generally taken early in the day. Because it makes you urinate more, a morning dose limits the need to get up during the night, which is called nocturia. In hypertension, the usual starting dose ranges from 12.5 to 25 mg once a day, and the treatment is usually taken once or twice a day depending on the prescription.
Consistency is key. The drug controls blood pressure as long as it is taken, it does not cure it: you must therefore continue even when feeling well, and never stop it on your own initiative. The doctor may combine it with a low-salt diet, which reinforces the effect on blood pressure. Any change in dose requires medical advice.
Why potassium and magnesium fall
By changing the way the kidney works, the thiazide alters the handling of several minerals. The sodium it prevents from being reabsorbed reaches farther along the nephron, where it is partly exchanged for potassium: potassium then passes more into the urine, which can lower its concentration in the blood, a hypokalemia. Magnesium follows a similar movement, and its urinary elimination also increases, hence a possible hypomagnesemia.
The drug can also lower blood sodium, a hyponatremia more pronounced in older people and those with a low intake, and raise blood calcium, a hypercalcemia. Potassium and magnesium remain the two minerals to watch closely. The extent of the decline depends on the dose, and laboratory monitoring keeps it in check. Diet remains the simplest way to rebuild these reserves.
The other effects to be aware of
The treatment can modestly raise fasting blood glucose, a dose-related effect that warrants monitoring in people with diabetes. It can also increase the level of uric acid in the blood and trigger gout attacks, especially during the first weeks and in a dose-dependent way. Finally, modest and dose-dependent rises in total cholesterol and triglycerides are observed.
Rarer effects also exist. Cases of acute myopia and secondary angle-closure glaucoma have been reported, typically in the days following the start of treatment. In addition, the FDA has flagged a slight increase in the risk of non-melanoma skin cancer, in particular squamous cell carcinoma, especially in fair-skinned people.
Interactions and monitoring
Several combinations call for caution. With lithium, diuretics reduce its renal elimination and greatly increase the risk of toxicity: the combination is not recommended. The induced hypokalemia can exaggerate the heart's response to the toxic effects of digitalis agents such as digoxin. Nonsteroidal anti-inflammatory drugs can dampen the diuretic and antihypertensive effect. In people with diabetes, the dose of the antidiabetic drug may need to be adjusted, and corticosteroids intensify the loss of potassium. Cholestyramine and colestipol reduce the digestive absorption of the drug, by up to 85 % and 43 % respectively, which requires spacing out the doses.
Monitoring frames all of this. It includes measuring sodium, potassium, calcium, and magnesium at the start and then at regular intervals, fasting blood glucose in people with diabetes, surveillance of kidney and liver function, and looking for signs of gout during the first weeks. This laboratory framework makes it possible to adjust the dose and to spot an imbalance early.
Sources
Related molecules
To explore in the « Heart and blood pressure » family and its neighbours.
See the whole « Heart and blood pressure » family · Back to the atlas
Supplements to consider
Beyond the plate, a single isolated nutrient can be worth discussing, to confirm with your doctor or pharmacist. Here is which one and in which form.
Magnesium
Magnesium is a mineral involved in many enzymatic reactions. Supplements differ mainly by their salt: organic forms such as bisglycinate and citrate are better tolerated digestively and better absorbed than oxide.
Preferred form bisglycinate or citrate rather than oxide
Potassium
Potassium is an electrolyte mineral. As a supplement, potassium citrate is a well-tolerated and bioavailable form; the elemental potassium content per capsule remains moderate owing to regulatory limits.
Preferred form potassium citrate
Frequently asked questions
What is hydrochlorothiazide used for and what are its side effects?
Hydrochlorothiazide is a thiazide diuretic prescribed for high blood pressure and certain types of edema. The package leaflet notably lists dizziness, a drop in blood pressure at the start of treatment and possible electrolyte imbalances. For the full list and what applies to you, refer to the package leaflet and speak with your doctor or pharmacist.
What interactions should you know about with hydrochlorothiazide?
The package leaflet flags interactions with certain NSAIDs, lithium, corticosteroids, other diuretics and antidiabetic medicines, which can alter tolerance or your mineral salt balance. Report all your treatments, including over-the-counter ones, to your doctor or pharmacist before combining anything.
Can you take hydrochlorothiazide during pregnancy?
Hydrochlorothiazide is not recommended during pregnancy and the package leaflet indicates a contraindication in the second and third trimesters. If you are pregnant, planning to be or breastfeeding, do not stop anything on your own and consult your doctor promptly.
What should you do if you miss a dose or want to stop hydrochlorothiazide?
If you miss a dose, the package leaflet advises against doubling the next one. Stopping a treatment for high blood pressure is not a decision to make alone, as your blood pressure may rise again. Any change should be discussed with your doctor or pharmacist.
Does hydrochlorothiazide affect potassium and magnesium?
Pharmacological literature describes that thiazide diuretics increase urinary elimination of potassium and, to a lesser degree, magnesium. This is why medical follow-up often includes a blood test for these minerals. This blood test, and the interpretation that follows from it, are the responsibility of your doctor.
Which nutrient and which form to consider during long-term treatment?
Depending on the results of your blood work, the nutrient most often considered is magnesium, in a well-tolerated form such as bisglycinate, and sometimes potassium. It is preferable to stay with a single active ingredient rather than a complex, and to validate any supplementation with the person managing your treatment, since excess potassium can be problematic.
Ces réponses portent sur le volet nutritionnel. Pour toute question sur votre médicament, la notice et votre médecin ou pharmacien font foi.