Amiloride

Designed to be used in combination with other diuretics and antihypertensive treatments, amiloride helps to reduce fluid retention while conserving potassium to reduce the risk of hypokalemia.

Overview

Amiloride is a diuretic usually used with antihypertensive medicines to treat hypertension (high blood pressure). It works by increasing the flow of urine, which reduces the amount of fluid in the body.

Fluid retention worsens high blood pressure because it constricts blood vessels and makes it harder for the heart to pump blood around the body. By reducing fluid throughout the body, blood vessels can dilate and blood can flow more efficiently. However, when used alone amiloride has weak beneficial effects on hypertension; it is only useful when combined with other antihypertensive agents.

Amiloride is an antikaliuretic diuretic, which means it increases urination while conserving potassium levels in the blood. It is therefore particularly useful when combined with thiazide diuretics or kaliuretic-diuretic agents, both of which can lower potassium levels and cause a condition known as hypokalemia, which can be life-threatening. It can help to restore normal potassium levels in patients with hypokalemia, or it can prevent hypokalemia in patients who may be at an increased risk of complications should their potassium levels fall while taking thiazide or kaliuretic diuretics. When taken alone, amiloride could result in hyperkalemia, which is abnormally high potassium levels.

Sometimes amiloride is also used in patients with congestive heart failure who are suffering from edema. Edema is excessive fluid retention which causes the body’s tissues to swell. It is common in patients with congestive heart failure, because blood is not pumped as effectively throughout the body.

In the US, amiloride is known by the brand name Midamor. It is only available with a doctor’s prescription, and it is administered in tablet form.

Condition(s) treated?

  • Hypertension
  • Edema (associated with congestive heart failure)

Type of medicine?

  • Antikaliuretic (potassium-conserving) diuretic

Side Effects

Hyperkalemia (high potassium levels) is one of the greatest risks associated with amiloride, and patients should familiarize themselves with the symptoms of this condition. If they notice signs of hyperkalemia they should speak to their doctor urgently. If symptoms are very severe, seek emergency care. If left untreated, the condition can lead to heart failure or paralysis and can even cause the heart to stop.

Symptoms of hyperkalemia include:

  • Difficulty breathing
  • Chest pain
  • Heart palpitations or irregular heartbeat
  • Unusual tiredness or weakness
  • Numb or tingling sensation

Serious side effects

There are many other side effects of amiloride, many of which are harmless, but some of which may require medical attention. The following are side effects which are reasonably common and which should be reported to your doctor urgently:

  • Abdominal pain
  • Nausea or vomiting
  • Confusion
  • Nervousness
  • Shortness of breath
  • Weak or heavy sensation in the legs

The following side effects are less common, but should still be referred to your doctor urgently:

  • Agitation
  • Irritability
  • Changes in mood or mental state
  • Back pain
  • Stiff neck
  • Blurred vision
  • Dizziness
  • Drowsiness
  • Fever
  • Hallucinations
  • Labored breathing
  • Wheezing
  • Chest tightness
  • Seizures

The following side effects are rare or incredibly rare and require urgent medical attention:

  • Pain in jaw or arm
  • Severe stomach pain
  • Black, tarry stools
  • Clay-colored stools
  • Constipation
  • Vomiting blood or material that resembles coffee grounds
  • Dark urine
  • Difficult urination
  • Burning sensation during urination
  • Severe tingling, numbness or burning, crawling or itching sensations
  • Rash
  • Sores, white spots or ulcers on lips or in mouth
  • Abnormal bruising or bleeding
  • Pale skin
  • Yellow skin or eyes
  • Changes in vision or loss of vision
  • Chest pain or heaviness
  • Cough
  • Sore throat
  • Swollen or painful glands
  • Shakiness or trembling in hands, arms, legs or feet
  • Chills
  • Cold sweats
  • Fainting
  • Rapid, pounding or slow heartbeat
  • Loss of appetite

Minor side effects

Many side effects of amiloride are minor and don’t require medical attention. Often, they will reduce in severity or go away completely once your body adjusts to the medication. You may want to consult your doctor if they persist or if you feel that they are having a significant impact on your life. In these instances, your doctor may be able to recommend lifestyle changes to reduce the side effects, or they may consider prescribing you an alternative drug or treatment. It’s important to weigh up all the benefits of the drug against the side effects; if it is of significant importance to your health, it may be preferable to continue taking the drug despite the side effects.

The most common minor side effects of amiloride are weight loss and diarrhea. Since the drug works to reduce fluid retention, it is natural that you may lose weight, particularly during the first few days of starting the medication. Diarrhea is not usually something to worry about unless it becomes persistent. In this instance, consult your doctor because prolonged diarrhea may lead to dehydration. You could include more soluble fiber in your diet to reduce diarrhea. This can be found in oat bran, barley, beans, nuts, seeds lentils and peas.

Some more minor side effects, which are uncommon, include:

  • Acidic or sour stomach
  • Belching or excess gas
  • Bloating
  • Indigestion
  • Appetite changes
  • Stuffy nose
  • Ringing or buzzing in ears
  • Hearing loss
  • Abnormal perception of color
  • Double vision
  • Tunnel vision
  • Night blindness
  • Overbright appearance of light or seeing halos around lights
  • Reduced sex drive
  • Inability to attain or maintain an erection
  • Feeling sad, empty or discouraged
  • Difficulty concentrating
  • Sleepiness or drowsiness
  • Trouble getting to sleep
  • Hair loss or thinning hair
  • Joint pain
  • Ache in legs, neck or shoulder
  • Swelling in breasts (can affect men and women)

If you notice any other side effects not listed here or in the information leaflet provided with your amiloride prescription, consult your doctor. You can also contact the FDA to report additional side effects.

Symptoms of amiloride overdose

Overdose of any drug, including amiloride, can be very dangerous. If you think you may have taken too much amiloride, consult your doctor even if you feel well. Symptoms of amiloride overdose include:

  • Decreased urination
  • Dry mouth
  • Extreme thirst
  • Increased heart rate
  • Lightheadedness
  • Cramps or pain in muscles
  • Rapid breathing
  • Sunken eyes
  • Wrinkled skin

Increased urination

Amiloride is designed to increase the frequency of urination, and this is probably what you will notice first when you begin taking the drug. Often, the increased frequency reduces after you’ve been taking the drug for a short time. Consider taking the medication before 6pm to avoid disturbing your sleep with frequent trips to the bathroom.

Dosage

For adults with hypertension or edema, the recommended starting dosage of amiloride is 5 mg once per day. This may be increased or reduced depending on the severity of your condition and the other medications you are taking. Always follow your doctor’s recommendation.

For children, the dose of amiloride must be determined by the doctor. It might depend on the age of the child and the severity of their condition.

Amiloride should be taken with food. You should try to take it at the same time every day in order to make it a part of your routine and to reduce the risk of missing a dose. Since the drug is a diuretic and will increase the frequency at which you urinate, it may be helpful to take it before 6pm so that your sleep is less likely to be disturbed.

If you miss a dose of amiloride, take it as soon as you remember. However, if by the time you remember it is almost time for your next dose, simply skip the dose and continue with your original dosing schedule. Do not double doses of amiloride to compensate for missed ones.

Additional lifestyle changes

Any treatment for hypertension is designed to manage the condition, rather than cure it. In many instances, doctors will recommend that patients make lifestyle changes that will help to rectify hypertension. This might include:

  • Losing weight
  • Doing more exercise
  • Eating less sodium (salt)
  • Adopting a more balanced diet

Your doctor will be able to advise you on diet plans and exercise regimes which are safe for you, considering your medical history, the medications you are taking and the other health problems, if any, you currently have. Always consult your doctor before making significant changes to your lifestyle which could affect your health. In regard to exercise, it is usually safest to start with small bursts of low-intensity exercise and gradually increase the intensity of workouts as your overall health and fitness improves.

Interactions

Some medicines conserve or increase the amount of potassium in the blood and, when taken with amiloride, pose a risk of hyperkalemia (high potassium levels). In worst cases, hyperkalemia can be fatal. Examples of such medicines include:

Angiotensin-converting enzyme (ACE) inhibitors (used to treat hypertension) such as:

  • Benazepril (Lotensin)
  • Captopril (Capoten)
  • Enalapril (Vasotec)
  • Fosinopril (Monopril)
  • Lisinopril (Prinivil, Zestril)
  • Moexipril (Univasc)
  • Perindopril (Aceon)
  • Quinapril (Accupril)
  • Ramipril (Altace)
  • Trandolapril (Mavik)

Angiotensin II receptor antagonists/ARBs (used to treat hypertension) such as:

  • Azilsartan (Edarbi)
  • Candesartan (Atacand)
  • Eprosartan
  • Irbesartan (Avapro)
  • Losartan (Cozaar)
  • Olmesartan (Benicar)
  • Telmisartan (Micardis)
  • Valsartan (Diovan)

Cyclosporine (immunosuppressant used in patients who have had organ transplant)
Other potassium-sparing diuretics such as:

  • Eplerenone (Inspra)
  • Spironolactone (Adactone)
  • Triamterene (Dyrenium)

Potassium supplements

Nonsteroidal anti-inflammatory drugs (NSAIDs) can reduce the effectiveness of diuretics such as amiloride and they may also increase the risk of hyperkalemia and kidney problems. Examples of NSAIDs include:

  • Aspirin
  • Celecoxib (Celebrex)
  • Diclofenac (Cambia, Cataflam, Voltaren-XR, Zipsor, Zorvolex)
  • Ibuprofen (Motrin, Advil)
  • Indomethacin (Indocin)
  • Ketoprofen (Active-Ketoprofen)
  • Naproxen (Aleve, Anaprox, Naprelan, Naprosyn)
  • Oxaprozin (Daypro)
  • Piroxicam (Feldene)
  • Salsalate (Disalsate)

Quinidine (used to treat irregular heartbeats) and lithium (psychiatric medication) can both reduce the renal clearance of amiloride. This means that they can increase toxicity and side effects of the drug. They are therefore not recommended for concurrent use.

Increased risks for hyperkalemic, diabetic or renal-impaired patients

Amiloride is not recommended for individuals with diabetes, kidney disease or other kidney problems. This is because the drug’s potassium-conserving properties may be accentuated in these patients. Similarly, individuals who already have abnormally high potassium levels of hyperkalemia should not take amiloride.

Warnings

Risk of electrolyte imbalance

Some patients are at an increased risk of electrolyte imbalance if amiloride is used concurrently with other diuretics and they have:

  • Liver cirrhosis
  • Ascites (buildup of fluid in abdomen)
  • Metabolic alkalosis (elevated pH levels in tissues)
  • Resistant edema (cases of fluid retention which are resistant to diuretics)

If amiloride must be administered with other diuretics in these patients, careful, ongoing monitoring of serum electrolytes and BUN levels is vital.

Using amiloride during pregnancy and breastfeeding

Although there have been no studies in the effects of amiloride on the fetus of pregnant women, animal studies have found that the fetus is unharmed when the drug is administered during pregnancy. Due to the lack of human studies, the drug is classed as pregnancy category B, which means that it could pose a small risk to the fetus and should therefore only be used if clearly needed.

Similarly, animal studies have found that amiloride is secreted in animal milk, but it isn’t known if it’s secreted in human milk. If it is, the effects of the drug on a nursing infant are unknown. For this reason, it is not recommended to take amiloride while breastfeeding. Instead, the drug should be discontinued, or the patient should discontinue nursing.

Children and amiloride

There is not enough evidence as to the safety and effectiveness of amiloride in children. For this reason, the drug is to be avoided in those under the age of 18 unless the potential benefits of the drug justify the potential risks. In these instances, doctors will establish dosing on a case-by-case basis.

The elderly and amiloride

Although evidence suggests that the effectiveness of amiloride is no different in the elderly than it is in younger adults, caution must be taken when administering the drug to geriatric patients. This is because elderly people tend to have impaired or decreased renal function, which could increase the risk of toxicity. Dosages for the elderly should therefore begin at very low levels and be gradually increased where necessary. Tests to assess renal and hepatic function may be administered before the drug is prescribed, and renal function should be monitored regularly once the patient has started amiloride therapy.

Storage

Amiloride should be stored in a closed container and in a dry, room-temperature environment away from direct light. Avoid storing it in the bathroom where it could be affected by excessive moisture and humidity.

All medicines, including amiloride, should be kept away from pets and children. Use containers with childproof safety caps where possible, and store the medicine up and away from the ground where it is not within easy reach of children or pets. This drug is only available with prescription and could be harmful if consumed by someone it is not intended for, so do not share it with other people.

Do not hold onto expired or unused amiloride. Instead, ask your healthcare provider for advice on how to safely dispose of it. Do not flush it down the toilet, pour it down the drain or put it in the trash without consulting your healthcare provider.

Summary

Amiloride is a potassium-conserving diuretic, which means that it works to rid the body of excess retained fluid without reducing potassium levels. It is usually prescribed to people with hypertension or edema caused by congestive heart failure, and tends to be combined with other diuretics and anti-hypertensive treatments.

Since it is a diuretic, the most common side effect associated with amiloride is increased urination. This is perfectly normal, and often dissipates after a short while. The drug may also cause diarrhea, weight loss, bloating and indigestion.

One of the biggest risks associated with amiloride is hyperkalemia, which is abnormally high levels of potassium in the blood. If left untreated, hyperkalemia can be fatal. To minimize this risk, patients should not take amiloride at the same time as other medicines which increase or conserve potassium levels. This includes ACE inhibitors, ARBs, Cyclosporine, other potassium-conserving diuretics, and potassium supplements. NSAIDs, quinidine and lithium are also unsuitable for concurrent use with amiloride, because they may increase the potency of the drug or increase the risk of toxicity and side effects.

The recommended dose of amiloride for adults is 5 mg taken once each day with food. Children may be prescribed the drug in rare instances. Pregnant women can take the drug if absolutely necessary, but there are potential risks to the fetus. In elderly patients and those with decreased renal function, dosages should begin at the lower range due to the increased risk of toxicity.

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Last Reviewed:
December 10, 2017
Last Updated:
December 22, 2017