A Closer Look at Thiazide Diuretics

• Diuretics work by triggering water and electrolyte excretion from your kidneys. Therefore, they are a primary drug of choice in the treatment of hypertension, heart failure, edema, and renal disease. 
• Among the diuretics, thiazide diuretics are the most commonly used because of their antihypertensive effect. 
• Sometimes they are also known as “low ceiling diuretics” because increasing the dose more than the therapeutic dose does not show further diuretic response. 

What Are Thiazide Diuretics?

Diuretics work by triggering water and electrolyte excretion from your kidneys. Therefore, they are a primary drug of choice in the treatment of hypertension, heart failure, edema, and renal disease.  

We might use them alone or in combination with other drugs, depending on the condition. 

Here, we will discuss the indications, mechanism of action, nursing assessments, and implementations of thiazide diuretics.  

Among the diuretics, thiazide diuretics are the most commonly used because of their antihypertensive effect. They show effects not only by diuresis but also by reducing peripheral vascular resistance in long-term therapy. Thiazide diuretics are sulfonamides. But they do not show hypersensitivity reactions in patients having an allergy to sulfa antimicrobial drugs.  

All thiazide diuretics affect the distal convoluted tubules. And all have equal maximum diuretic effects, differing only in potency. However, sometimes they are also known as “low ceiling diuretics” because increasing the dose more than the therapeutic dose does not show further diuretic response.  

The examples of thiazide diuretics are: 

• bendroflumethiazide 
• chlorothiazide 
• hydrochlorothiazide 
• hydroflumethiazide 
• methyclothiazide 
• polythiazide

Thiazide-like diuretics include: 

• chlorthalidone 
• indapamide 
• metolazone 

Indications

Thiazide and thiazide-like diuretics are indicated in:

• Nephrotic syndrome 
• Edema and ascites caused by hepatic cirrhosis 
• Hypertension 
• Diabetes insipidus, especially nephrogenic diabetes insipidus 
• Edema from right-sided heart failure 
• Mild to moderate left-sided heart failure
  

Mechanism of Action of Thiazide Diuretics

The thiazide and thiazide-like diuretics work by acting mainly in the cortical diluting segment of the nephron. They act at the distal convoluted tubule to decrease the reabsorption of Na+ by inhibition of a Na+/Cl− co-transporter.  

Their actions include: 

• Inhibition of the reabsorption of sodium and chloride ions, producing hyperosmolar or concentrated urine.  
• Increased urine output that decreases blood volume- due to increased water excretion. 
• Decreased urinary calcium excretion- by promoting the reabsorption of Ca2+ in the distal convoluted tubule, where parathyroid hormone regulates reabsorption. 
• Reduced peripheral vascular resistance- caused by the relaxation of arteriolar smooth muscle.
  

Side Effects of Thiazide Diuretics

The side effects of thiazide diuretics are:

• Hyperuricemia 
• Hypokalemia 
• Hypomagnesemia 
• Hyperglycemia 
• Hyponatremia  
• Hypercalcemia 
• Dehydration  
• Hypotension  
• Hypertriglyceridemia 
• Photosensitivity  
• Decreased libido 
• Azotemia  

Potassium wasting is a serious side effect of thiazide diuretics. Therefore, you should periodically monitor the serum potassium levels. However, more frequently, initially. To replenish potassium stores, you can prescribe a potassium supplement or a potassium-sparing diuretic.  

Nursing Assessment

• You need to monitor the patient’s daily weight each morning, soon after he voids, and before breakfast. Use the same scale every day and ensure they wear the same clothing. Keeping an eye on the body weight of the patient can help you know their response to diuretic therapy.  
• Assess the patient daily for lung sounds, skin turgor, intake and output ratio, location, and amount of edema. 
• Monitor the patient for signs of electrolyte imbalance, such as anorexia, muscle weakness, numbness, tingling, paresthesia, confusion, and excessive thirst. 
• If you give thiazide diuretics for hypertension, monitor the patient’s blood pressure and pulse before and after the administration.  
• Monitor laboratory tests before and periodically throughout the course. The most common tests involve electrolytes (especially potassium), blood glucose, BUN, and serum uric acid levels. 
• Thiazide diuretics may increase serum cholesterol, low-density lipoprotein (LDL) cholesterol, and triglyceride concentrations. Therefore, you need to keep an eye on them.  
• If the patient receives digoxin concomitantly with thiazide diuretics, monitor their serum digoxin levels. And if the patient has diabetes, monitor their serum glucose levels frequently because diuretics can cause hyperglycemia.  

Nursing Implementation

• Give the diuretic in the morning to prevent nocturia that might disturb the patient’s sleep.  
• Ask the patient to consult a dietician so that they can devise a potassium-rich diet to prevent hypokalemia.  
• To keep the potassium levels within normal limits, administer supplements.  
• Keep the bedpan or a urinal with the patient, or make sure they have easy access to the bathroom. 
• Ask the patient to linger, especially when standing up from sitting or lying straight, because your blood pressure might drop because of orthostatic hypotension. Also, tell them that standing for a long time or exercising in hot weather can worsen it. Therefore, they must avoid it.  
• Caution the patient to wear sunscreen when going under the sun because thiazide diuretics can cause photosensitivity reactions.  
• Ask them to drink plenty of fluids to prevent dehydration.  

The Bottom Line

Thiazide diuretics play an essential role in the management of hypertension and various other health conditions. However, with their therapy, take care of other parameters too.  

Compel your patients to attend follow-up visits from time to time so that you can monitor them well. 

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