Hydrochlorothiazide

What Does Hydrochlorothiazide Do?

Hydrochlorothiazide is a diuretic commonly used to treat conditions causing hypertension and fluid retention such as heart disease, liver cirrhosis and kidney disease. Its function is to encourage the body to excrete more salt and water in the urine, thus reducing overall fluid volume. As the heart weakens, fluid retention can occur. Blood pressure medication can also cause fluid retention. Off-label benefits consist of treating diabetes insipidus, some kidney stones and preventing hypokalemia.

How Does Hydrochlorothiazide Work? (the complicated stuff)

Hydrochlorothiazide inhibits the sodium-chloride symporter in the kidney's distal convoluted tubule, preventing sodium and chloride ions absorption into the bloodstream. This increases sodium, chloride, and water excretion in the urine, reducing fluid volume and consequently lowering blood pressure. In addition, the decreased intravascular volume reduces heart preload, potentially benefiting heart failure management.

Drug Type and Category of Hydrochlorothiazide

Hydrochlorothiazide is a diuretic medication - specifically, the 'thiazide diuretics' category.

What dosage of Hydrochlorothiazide should you be taking?

NICE Guidelines ¹

Adult Dosage

For Hypertension:

• Initial Dose: 25 mg orally once daily.
• Maintenance Dose: May be increased to 50 mg daily, either as a single dose or divided into two doses. Generally, doses above 50 mg are not needed when used with other antihypertensive medications.

For Oedema:

• Usual Dose: 25 mg to 100 mg orally once or twice daily. Some patients may benefit from intermittent therapy (e.g., administration on alternate days).

For Nephrocalcinosis:

• Initial Dose: 25 mg orally once daily.
• Maintenance Dose: May increase to 50 mg twice daily.

For Osteoporosis:

• Initial Dose: 25 mg orally once daily.
• Maintenance Dose: May increase to 50 mg daily.

For Diabetes Insipidus:

• Initial Dose: 50 mg orally once daily.
• Maintenance Dose: May increase to 100 mg daily.

Pediatric Dosage

For Edema and Hypertension:

• Infants (<6>
• Children (2-12 years): 1 to 2 mg/kg/day, with a maximum of 100 mg/day.

Administration Considerations

Hydrochlorothiazide is typically taken in the morning to minimise nocturia (needing to urinate frequently during the night). Regular monitoring of electrolytes is recommended, especially in elderly patients and those on higher doses.

What are the side-effects of Hydrochlorothiazide?

Common Side Effects

• Low Blood Pressure: May lead to dizziness, lightheadedness, or fainting.
• Increased Urination: A common effect due to its diuretic properties.
• Electrolyte Imbalances: Changes in potassium, sodium, magnesium, and calcium levels can occur, leading to symptoms like weakness, muscle cramps, and confusion.
• Increased Blood Sugar Levels: This can be particularly concerning for patients with diabetes.

Serious Side Effects

• Dehydration and Kidney Issues: Symptoms include reduced urination, increased thirst, dry mouth, and confusion, which may indicate worsening kidney function.
• Severe Skin Reactions: Such as Stevens-Johnson syndrome, characterised by painful rashes, blistering, and peeling skin.
• Vision Problems: Hydrochlorothiazide can cause blurred vision and may increase the risk of glaucoma, leading to eye pain and trouble seeing.
• Pancreatitis: Symptoms may include severe abdominal pain, nausea, and vomiting.
• Allergic Reactions: Severe reactions can include difficulty breathing, swelling of the throat or tongue, and hives.

Drug Interactions

Major Drug Interactions

• Other Antihypertensives: Combining hydrochlorothiazide with other blood pressure medications can lead to excessive hypotension.
• Diabetes Medications: Hydrochlorothiazide may reduce the effectiveness of certain diabetes medications, potentially leading to increased blood sugar levels.
• Lithium: Hydrochlorothiazide can increase lithium levels in the blood, raising the risk of lithium toxicity.
• Nonsteroidal Anti-Inflammatory Drugs (NSAIDs): The use of NSAIDs can reduce the antihypertensive effect of hydrochlorothiazide and may lead to renal impairment.
• Corticosteroids: Concurrent use may exacerbate electrolyte imbalances, particularly hypokalemia (low potassium levels).
• Digoxin: Hydrochlorothiazide can increase the risk of digoxin toxicity, especially in patients with low potassium levels.

Moderate Drug Interactions

• Aspirin: May increase the risk of renal impairment when used together.
• Antidepressants: Some antidepressants may interact and require dose adjustments.
• Antibiotics: Certain antibiotics can alter the effectiveness of hydrochlorothiazide.

Antacids, calcium supplements, or iron supplements should be taken 2 hours before or after hydrochlorothiazide to avoid decreased absorption.

Natural Alternatives to Hydrochlorothiazide ²

Ideally, the best way to not require this drug is to stay fit, healthy, exercise regularly and keep your weight down. Fitter people consistently show lower levels of heart disease than sedentary people. 

There are several natural compounds that may have diuretic and blood pressure lowering effects similar to hydrochlorothiazide, though they are generally less potent. Some potential natural alternatives include:

Vitamins and Minerals

• Vitamin B6: Works as a diuretic and can be used in combination with taurine and magnesium.
• Taurine: Has diuretic properties and can be used with vitamin B6. 
• Magnesium: Functions as a diuretic and is useful in combination with vitamin B6 and taurine.

Omega-3 Fatty Acids

Omega-3s from fish oil, particularly eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA), may have calcium channel blocker-like effects to help lower blood pressure.

Antioxidants

• Alpha-lipoic acid: May have calcium channel blocker-like effects to lower blood pressure.
• Coenzyme Q10 (CoQ10): Can act as a direct vasodilator to help reduce blood pressure.

Herbs and Botanicals

• Pycnogenol: May have angiotensin-converting enzyme (ACE) inhibitor-like effects to lower blood pressure.
• Garlic: Can be used in combination with ACE inhibitors, diuretics, or calcium channel blockers to help control blood pressure.

While these natural compounds may provide some blood pressure lowering benefits, it's important to note that their effects are generally milder compared to prescription medications. Additionally, their ability to improve cardiovascular outcomes has not been as extensively studied as conventional antihypertensive drugs.

Interesting facts about Hydrochlorothiazide

Hydrochlorothiazide has been in use since the 1950s, making it one of the oldest diuretics still commonly prescribed today. Its long history contributes to a well-understood safety profile.

Disclaimer

This article is generated for informational purposes only. It was created in December 2024. Medications and medical guidance can change over time. Therefore, it is essential to consult with your general practitioner or healthcare provider before making any decisions regarding medications or treatment plans. Your GP can provide personalised advice based on your specific health needs and conditions.

References

1. https://bnf.nice.org.uk/drugs/hydrochlorothiazide/
2. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3989080/