A Pharmacology Guide on Angiotensin Receptor Blocker Drugs

• Angiotensin receptor blockers block the vasconstrictive effects of aniotension II and plays a vital role in the treatment of hypertension. 
• Possible drug interctions are possible and should not administered with Lithium. 
• This drug should not be given to pregnant woman in their second or third trimester.  

Angiotensin receptor blockers, also known as ARBs, act by blocking the vasoconstrictive effects of angiotensin II. They have an advantage over ACE inhibitors, which only block the actions of one enzyme that produces angiotensin.  

However, ARBs act by completely blocking the actions of angiotensin – a protein hormone that causes your blood vessels to be narrower.   

Common examples of angiotensin receptor blocker drugs are:  

• Candesartan cilexetil  
• Eprosartan  
• Irbesartan  
• Losartan  
• Olmesartan  
• Telmisartan  
• Valsartan  

Angiotensin receptor blocker are a class of medications used to treat hypertension. They can also be used in patients with heart failure who can not tolerate ACE inhibitors. 

Angiotensin Receptor Blocker Mechanism of Action

Angiotensin receptor blockers block the receptor binding of angiotensin II to its receptors. Since angiotensin has vasoconstricting effects and secretes aldosterone, blood pressure increases. 

When it can not bind to its receptors in many tissues, including vascular smooth muscle and adrenal glands, its actions are blocked. This causes blood pressure to lower.   

Angiotensin receptor blockers do not inhibit the production of angiotensin-converting enzymes that convert angiotensin I to angiotensin II like ACE inhibitors do. Instead, they block the receptor sites of angiotensin II.   

ARBs are preferred over ACE inhibitors because they do not cause a breakdown in bradykinin. When bradykinin accumulates in the pulmonary tree, it causes cough – a common side effect of ACE inhibitors.  

Therefore ARBs are commonly used in patients having coughs with ACE inhibitors.   

For the treatment of hypertension, ARBs may be combined with other drugs, most commonly diuretics.   

• Valsartan may also be used in patients with heart failure as an alternative to ACE inhibitors.   
•  Losartan and Ibersertan are indicated in patients with diabetes because of their inherent renal protective effects. 
  

ARB Drug Interactions

When taking ARBs, these drug interactions can occur:  

• Losartan and Fluconazole, when given together, can result in increased losartan, leading to increased hypotensive effects. Therefore you should lower the dose of losartan when given with fluconazole.  
• NSAIDs can reduce the antihypertensive effects of ARBs.  
• ARBs and potassium supplements, when given together, can cause hyperkalemia.   
• Rifampin can increase the metabolism of Losartan, resulting in reduced hypotensive effects.   
• Lithium, when given with Losartan, can result in lithium toxicity.   

Angiotensin Receptor Blocker Side Effects

The common adverse drug reactions of angiotensin receptor blocker are:  

• Headache  
• Fatigue  
• Cough  
• Tickling in the throat  
• Angioedema  
• GI reactions  
• Increased serum potassium- To prevent it, you should ask the patient not to take a potassium-rich diet. Advise them to consume bananas and dates in moderation. Otherwise, it can result in hyperkalemia.   
• Transient elevations of BUN and serum creatinine levels  

Do not give ARBs in the second or third trimester to pregnant women. It can cause fetal injury and death.  

The Nursing Process When Administering an Angiotensin Receptor Blocker

Assessment

As a nurse, you should:  

• Obtain a baseline blood pressure, heart rate, and heart rhythm regularly. Check the patient for any adverse drug reactions.   
• Monitor the patient’s weight daily.  
• Keep an eye on the patient’s electrolyte and fluid status.   
• Observe if the patient tolerates the drug well and its therapeutic effects. Sometimes the dose needs to be adjusted. You should monitor their blood pressure daily to get insight into drug response.  
• If the patient has got a patch, watch them for pruritus. It might take several days for the patch to show its effects. In the meanwhile, they will require interim therapy. 
  

Implementations

• ARBs, if given orally, administer with food or at bedtime, as the physician directs.   
• When mixing and administering parenteral ARBs, follow the manufacturing guidelines.   
• Ask the patient not to make fast and sudden movements and help them get up because of orthostatic hypotension. Educate them on how they can overcome it.   
• With ARBs, ask the patient to follow non-pharmacological therapies such as exercise, salt, calorie reduction, and stress management to control blood pressure.   
• Know that doses might be adjusted according to the patient’s blood pressure readings and tolerance level.   
• To improve dose delivery through a transdermal patch, apply it with adhesive tape. Apply each to the different parts of the body. Remove the old patch completely when applying a new one to prevent drug overdose.   
• Before defibrillation, remove the transdermal patch to prevent arcing.   
• Make the patient perform eye movements periodically. 
  

The Bottom Line

As a nurse, you should make sure that the patient does not get any trauma due to orthostatic hypotension and has no injuries. Additionally, you should ensure he and his family have an understanding of drug therapy.   

ARBs remain essential agents in the treatment of hypertension, often combined with diuretics.

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