PTCB Guide to ACE Inhibitors.

What are ACE Inhibitors? 

ACE inhibitors are among the most widely dispensed medicines in the United States. Over 40 million people currently take an ACE inhibitor, with the drugs accounting for 35% of all prescriptions written for antihypertensive agents.

ACE inhibitors are easily identifiable because they all have the suffix –pril.  

There are four primary indications of ACE inhibitors:

• Hypertension –  to reduce blood pressure and the risk of stroke and/or heart attacks. 
• Chronic heart failure – to improve symptoms and prognosis. 
• Ischemic heart disease – to reduce further heart attack or stroke risks. 
• Diabetic nephropathy – to reduce proteinuria and worsening of the disease. 

For the PTCB exam, questions may focus on recognizing ACE inhibitors by their brand names, identifying them from a list of medications, or understanding their primary uses in treatment. Detailed questions on their mechanism of action will not be asked, though you are expected to know major side effects and drug interactions (see below).

That said, it is worth briefly exploring the mechanism in some basic detail to have a more robust grasp of this drug class.

Mechanism of Action.

As their name suggests, ACE inhibitors inhibit ACE – the angiotensin-converting enzyme.  

The ACE enzyme plays an important role in increasing blood pressure. Normally, the enzyme converts angiotensin I into angiotensin II. Angiotensin II has two broad effects: 

• Vasoconstriction – constriction of blood vessels, thereby increasing blood pressure. 
• Promoting the release of aldosterone – a hormone that plays a significant role in increasing blood pressure by encouraging the body to retain water and sodium. The more fluid the body retains, the higher blood pressure can become (this also explains why diuretics are effective at treating hypertension, because they encourage fluid loss from the body).  

By blocking the ACE enzyme, ACE inhibitors prevent these two hypertensive mechanisms. This reduces blood pressure, which also reduces the amount of work the heart has to do (hence why ACE inhibitors are also effective in treating patients with heart failure).

Side Effects.

One of the most common side effects of ACE inhibitors is a persistent, dry cough. This is because ACE inhibitors cause a build-up of bradykinin in the lung.

Other side effects of ACE inhibitors include: 

• Elevated potassium levels – hyperkalemia
• Increased risk of renal failure  
• Hypotension

“First-dose hypotension” refers to a heightened risk of hypotension after taking the very first dose of an ACE inhibitor. For this reason, patients are typically counselled to take their first dose before bedtime. 

ACE inhibitors increase potassium levels in the body (low aldosterone levels cause potassium retention) which, in turn, increases the risk of cardiac arrhythmias. ACE inhibitors should therefore not be taken with potassium supplements or other drugs – such as potassium-sparing diuretics – that also increase potassium levels.

Note that ACE inhibitors are not safe in hypertensive pregnant patients and so should be avoided i.e. they are teratogenic. There are only a small number of antihypertensive drugs safe for pregnant patients. These include:

• Nifedipine 
• Labetalol 
• Hydralazine 
• Methyldopa 

Memory tool: a widely used mnemonic to help you remember these is, “New Mothers Hate Labor” – “Nifedipine – Methyldopa – Hydralazine – Labetalol”.

Sample PTCB Exam Questions.

Below, we put together sample PTCB exam-style questions on ACE inhibitors. Learn more about the answer explanation of each in the section below.

Q1. What is the active ingredient of the medicine, Altace? 

a. Labetalol 

b. Ramipril 

c. Metformin 

d. Prednisolone 

Q2. ACE inhibitors can be identified as they all contain which suffix? 

a. -lol 

b. -pril 

c. -sone 

d. -ate 

Q3. Which of these side effects is associated with ACE inhibitors? 

a. Low potassium levels 

b. Hypertension 

c. Elevated glucose levels 

d. Persistent, dry cough 

Q4. ACE inhibitors are primarily used to treat conditions affecting which body system? 

a. Immune system 

b. Musculoskeletal system 

c. Cardiovascular system 

d. Central nervous system 

Q5. ACE inhibitors are avoided in patients with which condition?

a. Gestational hypertension

b. Chronic heart failure

c. Ischemic heart disease

d. Diabetic nephropathy

Answer Explanations.

Let’s go through each answer explanation in turn.

Answer to Question 1: b) Ramipril

Ramipril is the active ingredient of the medicine, Altace.

Answer to Question 2: b) -pril

ACE inhibitors are easily identifiable because they all contain the suffix -pril. Examples include ramipril, lisinopril, and perindopril.

Answer to Question 3: d) Persistent, dry cough

ACE inhibitors increase bradykinin levels in the lung. This causes many patients to develop a persistent, dry cough. If the cough becomes too burdensome for patients, they may be switched to an angiotensin receptor blocker such as candesartan or losartan.

Answer to Question 4: c) Cardiovascular system

ACE inhibitors are used to treat conditions such as hypertension and chronic heart failure. They work to reduce blood pressure, and so they are primarily used to treat conditions affecting the cardiovascular system.

Answer to Question 5: a) Gestational hypertension

ACE inhibitors are contraindicated in patients with gestational hypertension (high blood pressure in pregnancy). ACE inhibitors can cause harm to the developing fetus.

Tutorial Review.

Over the course of today’s PTCB guide to ACE inhibitors, we reviewed the key details you need to know about this widely prescribed drug class. As pharmacy technicians, you will handle and dispense ACE inhibitors daily. Knowing the key facts about this drug class is therefore essential knowledge.

In review, we learned:

• ACE inhibitors are drugs used in the treatment of cardiovascular diseases such as hypertension and chronic heart failure. They work to lower blood pressure i.e. they are antihypertensive agents.
• ACE inhibitors lower blood pressure by inhibiting the angiotensin-converting enzyme (ACE). By inhibiting ACE, blood vessels remain dilated, and aldosterone is prevented from being released. These dual effects lower blood pressure.
• Side effects of ACE inhibitors include a persistent, dry cough; elevated potassium levels, and hypotension (particularly after the first dose).
• ACE inhibitors are teratogenic and are therefore contraindicated in pregnant patients with hypertension.
• ACE inhibitors should be avoided with drugs or supplements that increase potassium (including potassium-sparing diuretics such as spironolactone and amiloride). Elevated potassium levels (hyperkalemia) increase the risk of cardiac arrhythmias.
• ACE inhibitors are easily identifiable because they all contain the suffix –pril – such as ramipril and fosinopril.

That concludes our PTCB review of ACE inhibitors. We hope you found this guide helpful in your pharmacy technician exam study.

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