How Does Fosinopril Work? (Monace) Uses, Side Effects, Precautions

How does Fosinopril work?

How Does Fosinopril Work?

Fosinopril is a type of drug called an ACE inhibitor that helps to lower the blood pressure by stopping the angiotensin II hormone from being produced. Angiotensin II usually causes the blood pressure to increase, so when fosinopril stops its formation, the blood pressure gets lower.

If you or someone you know needs to take fosinopril to help lower your blood pressure or improve your heart health, this page has most of the information that you’ll need.

Brand Names and Doses

Brand Dose IconFosinopril is the generic name, the active drug found in the medication. There are several different brand names that contain the same drug:

  • Fosipril
  • Monace
  • Monopril

Each of these brand medications contains fosinopril and work in the same way in your body. They’ve just got different names because they are manufactured by different companies.

There are two different doses available: 10mg and 20mg. When you first start taking fosinopril, you will probably start on the lower 10mg dose. This is because it can take some time for your body to adjust to the drug and taking a lower dose initially reduces the risk of side effect. A few weeks later, your doctor can help you to increase the dose until your blood pressure is in the healthy range.

Fosinopril is also available in combination with other drugs to lower your blood pressure, under these brand names:

  • Hyforil (fosinopril 10mg / hydrochlorothiazide 12.5mg)
  • Monoplus (fosinopril 10mg / hydrochlorothiazide 12.5mg)
  • Hyforil (fosinopril 20mg / hydrochlorothiazide 12.5mg)
  • Monoplus (fosinopril 20mg / hydrochlorothiazide 12.5mg)
  • Fosetic (fosinopril 20mg / hydrochlorothiazide 12.5mg)

This is a benefit if you need to take both fosinopril and hydrochlorothiazide to control your blood pressure because you can just take one tablet and you’ll be less likely to get confused.

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What type of drug is it?

Drug Type IconFosinopril is a type of drug called an angiotensin-converting enzyme (ACE) inhibitor, a group of medications that work in a similar way to lower blood pressure. Other medicines in the same class are:

Although each of these medications work in the same way, there are subtle differences between them, like how fast they work and how many times a day you need to take a dose.

How does it work?

How it works IconFosinopril and other ACE inhibitor drugs work to lower blood pressure by stopping a certain enzyme in the body from converting angiotensin I to angiotensin II. Angiotensin II is the active form, which usually helps to keep the blood pressure higher by tightening the blood vessels and increasing the amount of blood travelling through them.

When you take fosinopril, you don’t have as much angiotensin II in your body and it can’t work its effect of increasing the blood pressure as usual. As a result:

  • The muscles around your blood vessels relax, creating more room for the blood to pass through.
  • Your kidneys reabsorb less water and you excrete more in your urine, which means you will have less blood in your blood system.

This means that you will have less blood pumping around blood vessels that are roomier than usual. If you think of it like a plumbing system, that means there is going to be less pressure and help your heart.

Side Effects

Side Effects IconACE inhibitors have a broad action on the body and there are several side effects that can occur when you take fosinopril. The most important side effects are explained below, but you should check the medicine information leaflet for the complete list.

Low blood pressure (hypotension)

The most common side effects happen because it’s working too well and you end up with low blood pressure. You might notice symptoms of:

  • Headache
  • Tiredness
  • Dizziness
  • Flushing

These effects are most common when you first start taking fosinopril or if your dose has recently increased. They usually get better in a few days as your body gets used to the drug. If you still have these effects after more than a week, your blood pressure might be too low because you are taking a higher dose than you need. You can test your blood pressure to make sure (most pharmacies do this for free) and you can talk to your doctor if you need to lower the dose.

Excess Potassium (Hyperkalaemia)

Fosinopril causes more water to be excreted in the urine that usual, which can upset the balance of potassium in your body. Less potassium is excreted and it can build-up in your body, causing symptoms of tiredness and muscle weakness.

The best way to check if you have high potassium levels is to take a simple blood test, so simply have a chat with your doctor if you think you might have hyperkalemia.


It can cause some people to get a dry cough, which can be quite frustrating as it does not seem to go away. If you experience a cough and it annoys you, you can talk to your doctor about alternative medications like an angiotensin II channel blocker.


Cautions IconThere are a couple of things you should be aware of before you start taking fosinopril, as they can have serious consequences for some people. It’s best to know these things in advance!


Rarely, fosinopril can cause swelling of the mouth and throat called angioedema, which can stop you from breathing as normal. If you have suffered from angioedema before, you should not take fosinopril because you are more likely to experience it again. If you are taking the medication and you notice swelling around your mouth and face, stop taking it and see a doctor immediately.

Renal Impairment

Fosinopril puts extra pressure on the kidneys and increases the risk of renal impairment, particularly when used with other medications, such as NSAIDS and diuretics.  If you have poor kidney function, it is not likely to be the best choice of drug for you.

Stopping Suddenly

Fosinopril helps to manage high blood pressure over the long-term and should be taken every day. If you suddenly stop taking it, the amount of angiotensin II in your body will increase once again and cause more blood to push through smaller blood vessels. Your hypertension might be even worse than in the beginning because of the sudden change!

Instead, you should gradually reduce the dose over a few weeks when you want to stop taking fosinopril. If you take the 20mg dose now, decrease the dose to 10mg daily until your body feels normal and then you can stop completely.

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Drug Interactions

Drug Interactions IconLithium + Fosinopril Interaction

Fosinopril can decrease the amount of lithium that is excreted from the body, leading to high concentrations and increased risk of side effects. The dose of lithium can be reduced to manage this, or an alternative antihypertensive medication can be used.

Loop Diuretic + Fosinopril Interaction

Taking a loop diuretic drug and fosinopril together increases the risk of blood pressure that is too low, particularly for the first few doses. You may need a lower dose or to stop taking the loop diuretic for a few days when beginning to take the medication. Using both may also increase risk of renal impairment.

NSAID + Fosinopril Interaction

NSAIDs and fosinopril can sometimes be used together in young otherwise healthy patients, but it might not work as well to reduce your blood pressure.

Thiazide Diuretic + Fosinopril Interaction

Taking a thiazide diuretic and fosinopril together increases the risk of blood pressure that is too low, particularly for the first few doses, and may increase the risk of renal impairment. Using a lower dose is okay for some people but the combination is not recommended for others – it depends on your individual situation.

Pregnancy and Breastfeeding

Pregnancy IconYou should not take fosinopril if you are pregnant, breastfeeding or planning to become pregnant in the future. Doses in the first trimester may cause birth defects and later in the pregnancy can lead to renal dysfunction of the baby.

You can take fosinopril when you are breastfeeding. Very small amounts may be excreted in the breast milk, but no side effects have been reported. It is best to monitor for possible signs of low blood pressure in your baby, however, such as tiredness and irritability.

How Does Fosinopril Work?

About the author


Yolanda is a passionate medical writer who loves to help people understand how health and different treatments work. After graduating in Pharmacy in Australia, she moved to Italy to study the Mediterranean way of life and continue learning about health and medicine.

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