Introduction

Hypertension or High Blood Pressure is a prevalent but serious health affliction. When the force of blood against the blood vessels supplying organs is consistently above 140/90 mmHg, it is considered hypertension. It often goes undiagnosed and is therefore referred to as a “silent killer” because it can lead to serious health issues such as:¹

• Irregular heartbeat
• Angina or chest pain
• Heart attack
• Heart failure
• Stroke
• Kidney failure

Hypertension is managed using a combination of lifestyle modifications and pharmaceutical therapy, one of which is Diuretics.¹ Diuretics are a class of medications that increase the excretion of water and electrolytes from the body through urine, which reduces the total volume of fluid and salts in your bloodstream, thereby bringing down blood pressure.²

“Diuretics” is an umbrella term for several drugs within that class and each of these drugs has its pros and cons you, as a patient, should be educated on to make informed decisions about their health. This article will help you understand the different types of diuretics and which one might be the best considering your health status. 

Let’s dive into it!

What are diuretics?

Diuretics are drugs which increase the production and removal of water and sodium (which makes up salt) through urine, which is why they are also known as “water pills”.

Removal of large amounts of fluid from within the body’s circulation lowers the pressure on blood vessels, thereby combating hypertension.

Think of your arteries and veins as rubber pipes that supply blood to vital organs like kidneys, heart and liver, all of which are soft and easily damaged. When there is too much salt within these pipes, they hold on to too much water, far more than what it is meant to contain, it exerts enormous pressure on the walls of the pipes and eventually damages the organs.

When some of the salt is removed, a proportion of the water also moves out, reducing the pressure on the blood vessels and keeping blood pressure within a healthy range.

Diuretics achieve this through multiple mechanisms and therefore different types of diuretics can be used concurrently, all under the supervision of a medical practitioner.

Types of diuretics

Diuretics are categorised according to their mechanism and site of action into the following:

• Thiazide Diuretics
• Loop Diuretics
• Potassium-Sparing Diuretics

Thiazide diuretics

Thiazide diuretics decrease the kidney’s ability to reabsorb sodium and chloride, which increases fluid loss in urine and decreases total blood volume. This reduces the force with which the heart pumps out blood thereby, lowering blood pressure.³

Thiazide diuretics have been regarded as the primary choice of treatment for hypertension either singularly or in combination with other diuretics owing to:

• Their effectiveness in treating mild to moderate cases of hypertension
• They may even improve the heart function of cardiac patients
• Longer half-life, meaning that these medications do not need to be consumed frequently
• They are well tolerated and have low instances of adverse effects

Disadvantage of thaiazide

Thiazide drugs increase the removal of an essential element called potassium, which may lead to Hypokalemia, causing the heart to beat irregularly. This may lead to sudden death but these events are noted often in individuals who are taking high doses of thiazides.

It may also lead to muscle weakness as a large amount of sodium is lost, which is essential for muscle function.

Thiazides is not suitable if you:

• Have trouble producing urine
• Are allergic to sulfa drugs
• Have electrolyte imbalance
• Have blood clotting disorders like stroke, heart attacks
• If you consume medications like Digitalis and Lithium²

Hydrochlorothiazide, chlorthalidone, and indapamide are commonly used Thiazides.

Loop diuretics

This category of diuretics lowers blood pressure by increasing the removal of sodium and chloride, just like thiazide diuretics but loop diuretics are used to treat cases of severe hypertension as they are much more potent than Thiazide diuretics. Their potency makes them suitable for treating hypertension unaffected by other medications and conditions involving fluid buildup in kidney and heart failure.²

Disadvantages of loop diuretics

They are not preferred to treat mild to moderate cases of hypertension as they lead to electrolyte imbalances like

• Decreases sodium potassium and magnesium which causes muscle fatigue, irregular heartbeat, dizziness and constipation
• Decreases calcium, which can lead to weakened bones and muscle cramps
• Additionally, they may also cause skin photosensitivity (a condition where skin exposed to sunlight becomes red, blistered and starts peeling)
• Temporary or permanent deafness in individuals who take high doses of these drugs
• Gout- a type of arthritis, which causes intense pain, swelling and tenderness in smaller joints of the body like those of the toes and fingers

Therefore Loop diuretics are generally not an option to treat hypertension if you

• Have a history of allergy to Loop Diuretics
• Have liver failure
• Have Electrolyte imbalance⁴

Furosemide, Torsemide and Bumetanide are commonly used Loop diuretics.

Potassium-sparing diuretics

These diuretics enhance the removal of potassium and water in the kidneys while retaining sodium, causing a reduction in the total amount of fluid within the body leading to a decrease in blood pressure. They are weak compared to both thiazides and loop diuretics but they enhance the antihypertensive effects of both and help combat their side effects when used together.⁵

Potassium-sparing diuretics are divided into two types:

1. Aldosterone antagonists- Spironolactone and Eplerenone

These drugs act slowly but produce a consistent and prolonged reduction in blood pressure.² This is beneficial in cases of Refractory Hypertension, a condition where blood pressure remains dangerously high. This medicine is used in conditions like:

• Hypertension is caused by underlying medical conditions like kidney or hormonal disease
• Inconsistent consumption of medications
• Development of resistance to medications

2. Non-aldosterone antagonists- Amiloride and Triamterene

These drugs are not successful in reducing blood pressure but they prevent loss of potassium when used with Thiazides.

Due to potassium being retained, these drugs may result in:

• Muscle fatigue or in rare cases, paralysis ⁶
• Irregular heartbeat
• Gastrointestinal irritation leading to nausea and vomiting
• In severe cases, it can affect mental status

Disadvantage

Spironolactone and amiloride should not be used if

• You have high blood levels of potassium
• You are pregnant or breastfeeding
• Have kidney failure or cannot produce urine
• You have liver failure²

Spironolactone may also cause:

• Menstrual disturbances in women
• Erectile dysfunction, development of breasts and prostate enlargement in men²

Factors influencing the choice of diuretic

The following factors dictate which diuretic is the best for you:⁷

• Severity of hypertension - for mild to moderate hypertension, thiazides are the first choice but for severe cases, loop diuretics or a combination of thiazides and potassium-sparing diuretics are used
• Concurrent medical issues like kidney disease, liver disease, gout, and pregnancy
• Concurrent medications that you are on also influence the choice of diuretic to treat hypertension
• Your age may make some diuretics a noncontender due to their side effects like irregular heartbeat and muscle fatigue
• Your gender may make you more susceptible to side effects, like prostate enlargement
• Allergies to certain drugs, like sulfa drugs, may narrow your choices
• Cost of diuretic medication and insurance coverage
• Effects of lifestyle changes like low sodium diet, exercise, weight loss,⁸ and following medication instructions also affect the choice of diuretic to treat hypertension

Now that you have a better understanding of diuretics, you can feel more confident in discussing your treatment options with your doctor. If you are looking into using diuretics to manage your hypertension or switching from one type of diuretic to another, remember to consult with your doctor for personalized advice, monitoring of blood pressure and detection, and treatment of side effects.

Summary

Diuretics are medications used to treat hypertension by increasing the removal of excess water and salts to reduce blood pressure.

There are three main types of diuretics:

• Thiazide diuretics are the first choice for treating mild to moderate hypertension and work by reducing sodium and fluid retention but may cause potassium loss and subsequent muscle weakness. hydrochlorothiazide and chlorthalidone are commonly used
• Loop diuretics are more potent than thiazides and used for severe hypertension. They can cause significant electrolyte imbalances and are usually used in severe cases. Furosemide and bumetanide are commonly used
• Potassium-sparing diuretics are used in combination with other diuretics help to prevent potassium loss. They are weaker but help enhance the effects of thiazides and loop diuretics. Common examples include spironolactone and eplerenone

Choosing the right diuretic depends on factors such as the severity of hypertension, existing medical conditions, current medications, age, and potential side effects and lifestyle changes.