Co-amilofruse (Frumil)

How does it work?

Frumil tablets and Frumil LS tablets contain two active ingredients, amiloride hydrochloride and furosemide. Furosemide is a type of medicine called a loop diuretic, and amiloride is a type of medicine called a potassium-sparing diuretic. This combination of diuretics is also known as co-amilofruse. (NB. Co-amilofruse tablets are also available without a brand name, ie as the generic medicine.)

Diuretics are sometimes referred to as ‘water tablets’. They remove excess fluid from the body by increasing the production of urine.

Diuretics act in the kidneys. They work by causing the kidneys to increase the amount of salts, such as potassium and sodium, that are filtered out of the blood and into the urine. When these salts are filtered out of the blood by the kidneys, they draw water alongside them. As diuretics increase the removal of salts from the blood, they also cause more water to be drawn out of the blood and into the urine.

Loop diuretics like furosemide are strong diuretics that cause lots of potassium to be filtered out of the blood. This can sometimes cause the level of potassium in the blood to fall too low. A low blood potassium level is called hypokalaemia and can sometimes be dangerous, particularly for people with heart disease or liver disease.

Amiloride on the other hand, is a weaker diuretic that causes potassium to be retained in the body. It is used in combination with furosemide to prevent the amount of potassium in the blood from falling too low.

Co-amilofruse is used to treat conditions where excess fluid has been retained in the body (oedema) and where a drop in the amount of potassium in the blood could be dangerous.

For example, it is used in heart failure, where the pumping mechanism of the heart is less effective. This can cause fluid to build up in the ankles, causing swollen ankles, and in the lungs (pulmonary oedema), which makes it difficult to breathe. Furosemide helps the body to remove this excess fluid. Removing fluid from the blood vessels also decreases the pressure within the blood vessels. This makes it easier for a weak heart to pump blood around the body.

It is also used to remove excess fluid that can accumulate as a result of cirrhosis of the liver. This fluid may accumulate and cause swelling in the abdomen (ascites) or in the legs (peripheral oedema).

What is it used for?

  • Treating fluid retention (oedema) in conditions where it is important that the amount of potassium in the blood does not fall too low, for example in heart failure, liver cirrhosis, kidney disease, or oedema caused by treatment with corticosteroids or oestrogens.


  • As diuretics cause your kidneys to produce more urine, you may prefer to take this medicine in the morning rather than before going to bed, as this will reduce the likelihood of you needing to get up in the night to visit the toilet. Seek further advice from your doctor or pharmacist.
  • While you are taking this medicine your kidney function should be checked regularly.You should have regular blood tests to monitor your blood sugar and the levels of electrolytes such as potassium and sodium in your blood.
  • If you experience any of the following symptoms while taking this medicine you should inform your doctor promptly, so that the amount of fluids and salts in your body can be checked: thirst, lethargy, confusion, weakness, drowsiness, muscle cramps, scanty production of urine, nausea and vomiting, abnormal heart beats, or seizures.

Use with caution in

  • Elderly people.
  • Decreased kidney function.
  • People with liver cirrhosis and decreased liver function.
  • People with difficulty in passing urine (urinary retention).
  • Enlarged prostate gland (prostatic hypertrophy).
  • Low blood pressure (hypotension).
  • Gout.
  • Diabetes.
  • People at risk of developing an imbalance in the levels of electrolytes in their blood, eg due to severe diarrhoea or vomiting, or other medicines being taken (see below).
  • People with low levels of protein in their blood, eg due to a kidney disorder called the nephrotic syndrome.

Not to be used in

  • Children under 18 years of age.
  • Allergy to furosemide or amiloride.
  • Allergy to medicines from the sulphonamide group, eg the antibiotic sulfamethoxazole.
  • People with a low volume of fluid in their blood (hypovolaemia), eg due to blood loss or dehydration.
  • High levels of potassium in the blood (hyperkalaemia).
  • Very low levels of potassium in the blood (hypokalaemia).
  • Very low levels of sodium in the blood (hyponatraemia).
  • Kidney failure caused by poisoning with agents that have damaged the kidney or liver.
  • Kidney failure that is preventing the production of urine (anuria).
  • People who are losing consciousness due to liver cirrhosis that is affecting the brain.
  • Inadequate production of natural steroid hormones by the adrenal glands (Addison's disease).
  • Breastfeeding.
  • Rare hereditary problems of galactose intolerance, the Lapp lactase deficiency or glucose-galactose malabsorption (Frumil and Frumil LS tablets contain lactose).

This medicine should not be used if you are allergic to one or any of its ingredients. Please inform your doctor or pharmacist if you have previously experienced such an allergy.If you feel you have experienced an allergic reaction, stop using this medicine and inform your doctor or pharmacist immediately.

Pregnancy and breastfeeding

Certain medicines should not be used during pregnancy or breastfeeding. However, other medicines may be safely used in pregnancy or breastfeeding providing the benefits to the mother outweigh the risks to the unborn baby. Always inform your doctor if you are pregnant or planning a pregnancy, before using any medicine.

  • The safety of this medicine during pregnancy has not been established. The manufacturer states that it is not recommended during pregnancy. Seek medical advice from your doctor.
  • There is no information available about the safety of amiloride during breastfeeding. Furosemide passes into breast milk and may decrease the production of breast milk. For this reason, the manufacturer states that this medicine should not be used by women who are breastfeeding. Seek medical advice from your doctor.

Side effects

Medicines and their possible side effects can affect individual people in different ways. The following are some of the side effects that are known to be associated with this medicine. Just because a side effect is stated here does not mean that all people using this medicine will experience that or any side effect.

  • Increased production of urine.
  • Disturbances of the gut such as diarrhoea, constipation, nausea, vomiting or abdominal pain.
  • Dehydration.
  • Decrease in blood pressure.
  • Dizziness.
  • Drowsiness.
  • Weakness.
  • Dry mouth.
  • Headache.
  • Confusion.
  • Visual disturbances.
  • Muscle cramps.
  • Skin rashes.
  • Increased blood sugar level.
  • Increased level of uric acid in the blood (hyperuricaemia) which may cause gout.
  • Disturbances in the levels of electrolytes (eg potassium, calcium, magnesium) in the blood.
  • Pins and needles (paraesthesia).
  • Sensation of ringing or other noise in the ears (tinnitus).
  • Disturbance in the normal numbers of blood cells in the blood.

The side effects listed above may not include all of the side effects reported by the drug's manufacturer.For more information about any other possible risks associated with this medicine, please read the information provided with the medicine or consult your doctor or pharmacist.

How can this medicine affect other medicines?

It is important to tell your doctor or pharmacist what medicines you are already taking, including those bought without a prescription and herbal medicines, before you start treatment with this medicine. Similarly, check with your doctor or pharmacist before taking any new medicines while taking this one, to ensure that the combination is safe.

Amiloride can increase the amount of potassium in the blood. If this medicine is taken with any of the following, which can also raise potassium in the blood, the combination could cause the amount of potassium in the blood to rise too high (hyperkalaemia):

  • ACE inhibitors, eg captopril
  • angiotensin II receptor antagonists, eg losartan
  • ciclosporin
  • non-steroidal anti-inflammatory drugs (NSAIDs), eg indometacin
  • other potassium-sparing diuretics, eg spironolactone, triamterene (should not be taken while taking this medicine)
  • potassium salts, eg potassium citrate for cystitis
  • potassium supplements (do not take these while taking this medicine)
  • potassium-containing salt substitutes, eg lo-salt
  • tacrolimus.

Furosemide can decrease the amount of potassium in the blood. If this medicine is taken with any of the following medicines, which can also lower potassium in the blood, the combination could cause the amount of potassium in the blood to fall too low (hypokalaemia):

  • amphotericin
  • corticosteroids, such as hydrocortisone and prednisolone
  • beta 2 agonists, eg salbutamol, terbutaline
  • other diuretics, such as bendroflumethiazide
  • prolonged use of laxatives
  • theophylline.

If the level of potassium in your blood falls during treatment, this can increase the risk of adverse effects from digoxin or medicines for abnormal heart rhythms, eg amiodarone.

If this medicine is taken with carbamazepine the combination may cause the amount of sodium in your blood to fall too low (hyponatraemia).

Furosemide decreases blood pressure. If this medicine is used in combination with other medicines that lower blood pressure, either as a side effect, or to treat high blood pressure (antihypertensives), the combination might lower your blood pressure too much. This could make you feel dizzy or faint. If this happens to you tell your doctor, as your doses may need adjusting. Other medicines that decrease blood pressure include the following:

  • ACE inhibitors such as enalapril
  • alpha-blockers such as prazosin
  • alprostadil
  • angiotensin II receptor antagonists such as losartan
  • antipsychotics
  • baclofen
  • benzodiazepines, eg diazepam, temazepam
  • beta-blockers such as propranolol
  • calcium channel blockers such as nifedipine, diltiazem
  • clonidine
  • diazoxide
  • other diuretics, eg bendroflumethiazide
  • dopamine agonists, eg bromocriptine, apomorphine
  • hydralazine
  • levodopa
  • MAOI antidepressants, eg phenelzine
  • methyldopa
  • minoxidil
  • moxonidine
  • nicorandil
  • nitrates, eg glyceryl trinitrate.

If you are due to start treatment with an ACE inhibitor, eg captopril, or an angiotensin II receptor antagonist, eg candesartan, your doctor may ask you to stop taking this medicine temporarily, or reduce your dose for a few days beforehand. This is to avoid your blood pressure falling too low with your first dose of ACE inhibitor/angiotensin II blocker.

This medicine can increase blood glucose levels and people with diabetes may therefore need increases in their dose of insulin or antidiabetic tablets. Your blood sugar level should be monitored.

This medicine may increase the blood level of the medicine lithium. People taking lithium with this medicine should have the level of lithium in their blood closely monitored.

The diuretic effect of this medicine may be reduced by the following medicines:

  • non-steroidal anti-inflammatory drugs (NSAIDs), eg indometacin, ibuprofen, aspirin
  • phenytoin.

There may be an increased risk of side effects on the kidneys if this medicine is used in combination with the following medicines:

  • ACE inhibitors, eg captopril
  • certain antibiotics, eg aminoglycosides such as gentamicin
  • other diuretics
  • non-steroidal anti-inflammatory drugs (NSAIDs), eg indometacin.

There may be an increased risk of side effects on the ears if this medicine is used in combination with aminoglycoside antibiotics such as gentamicin.

There may be an increased risk of side effects on the kidneys and ears if this medicine is taken by people being treated with platinum-based chemotherapy such as cisplatin.

Other medicines containing the same active ingredients

Co-amilofruse tablets are available without a brand name, ie as the generic medicine.