Introduction

When it comes to any pharmacy licensing exam – including the NAPLEX – it’s vital that you have a comprehensive understanding of each major drug / drug class. Here, we focus on what you need to know about ACE inhibitors.

Captopril was the first FDA-approved ACE inhibitor, approved in 1981. Captopril was an inconvenient medicine, though – as it required multiple dosing per day. It was also associated with more side effects, such as a metallic taste. Since then, though, ACE inhibitors have come on leaps and bounds – now necessitating only once daily dosing and drugs that come with fewer risks / adverse effects.

Indications

ACE inhibitors are used in the treatment of the following indications:

• Hypertension – used as either first or second-line treatment. The purpose is clear: to reduce the risk of myocardial infarction, stroke and other ailments that result from cardiovascular disease.
• Chronic heart failure (CHF) – improving both symptoms and overall prognosis in patients with all stages of chronic heart failure.
• Ischemic heart disease – ACE inhibitors are used to reduce the risk of subsequent MI and stroke in at-risk patients.
• Diabetic nephropathy / chronic kidney disease (CKD) with proteinuria – reduce progression of nephropathy by reducing proteinuria.

ACE inhibitors may also be used for purposes not listed in this guide.

Mechanism of action

The mechanism of action of ACE inhibitors is clear – to prevent conversion of angiotensin I into angiotensin II.

Why is this inhibition important?

To answer this question, let’s review the effects of angiotensin II. Angiotensin II is responsible for the following effects:

• Angiotensin II causes vasoconstriction
• Angiotensin II causes aldosterone release
• Aldosterone is responsible for fluid retention

Reducing angiotensin II leads to lower peripheral vascular resistance (afterload), thus lowering blood pressure.

Reducing aldosterone also leads to dilation of the efferent glomerular arterioles, reducing intraglomerular pressure and slowing progression of chronic kidney disease (CKD).

Lowering aldosterone levels also increases sodium / water excretion – reducing fluid retention.

These effects, in turn, reduce venous return (preload) and pressure in patients with heart failure.

Dose

Dose varies depending on indication – however, the dose is often lower in heart failure compared to other conditions.

Ramipril – at 1.25mg daily – is common in heart failure or diabetic nephropathy. Higher doses, at 2.5mg per day, are often reserved for other conditions.

Dose may be titrated up to 10-20mg per day over a prolonged period, depending upon the patient’s condition, response and renal function.

Side effects

Side effects associated with ACE inhibitors include:

• Persistent dry cough – due to pulmonary kinin accumulation
• Hypotension – worst after the first dose
• Hyperkalemia – low aldosterone encourages potassium retention

Renal failure – either the cause / worsening factor, particularly in patients with existing renal artery stenosis

Rarely, angioedema and anaphylactoid reactions.

Clinical factors

Here are some of the essential factors to consider when prescribing ACE inhibitors:

• Avoid in patients with renal artery stenosis / acute kidney injury.
• Avoid in women who are, or plan, to become pregnant.
• Avoid in women who are breastfeeding.
• Employ a lower dose in patients with chronic kidney disease.
• Avoid with other drugs / supplements that enhance potassium levels – potassium supplements, potassium-sparing diuretics (amiloride, spironolactone etc.) – as ACE inhibitors cause hyperkalemia.
• First-dose hypotension may be worsened when taken with other diuretics and/or hypotensive agents.
• Taking ACE inhibitors with both an NSAID and a diuretic (so-called “triple-whammy effect”) increases the risk of renal failure.
• ACE inhibitors are taken orally. They may be taken with or without food. The first dose of an ACE inhibitor should be taken before bed due to hypotensive risk.

ACE inhibitors remain widely used medicines in cardiology. ACE inhibitors include drugs such as ramipril, lisinopril and perindopril – drugs that can have an enormous clinical impact on the patient. However, ACE inhibitor use is not without risk. Here, we’ve put together some of the key factors you – as a healthcare professional – must consider.

As a licensed pharmacist, you must always balance the risk:reward ratio to determine what works best for the patient in their unique circumstances.

NAPLEX Study Guide is the leading online resource to help pharmacy graduates pass their licensing exam. Check back to our NAPLEX blog soon for even more great tips, tricks and tutorials to help you become a professional pharmacist.