Hyperkalemia Like other potassium-conserving agents, amiloride may cause hyperkalemia (serum potassium levels greater than 5.5 mEq per liter) which, if uncorrected, is potentially fatal. Hyperkalemia occurs commonly (about 10%) when amiloride is used without a kaliuretic diuretic. This incidence is greater in patients with renal impairment, diabetes mellitus (with or without recognized renal insufficiency), and in the elderly. When amiloride is used concomitantly with a thiazide diuretic in patients without these complications, the risk of hyperkalemia is reduced to about 1-2%. It is thus essential to monitor serum potassium levels carefully in any patient receiving amiloride, particularly when it is first introduced, at the time of diuretic dosage adjustments, and during any illness that could affect renal function.
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warnings
The risk of hyperkalemia may be increased when potassium-conserving agents, including amiloride HCl, are administered concomitantly with an angiotensin-converting enzyme inhibitor, an angiotensin II receptor antagonist, cyclosporine or tacrolimus. (See PRECAUTIONS , Drug Interactions. ) Warning signs or symptoms of hyperkalemia include paresthesias, muscular weakness, fatigue, flaccid paralysis of the extremities, bradycardia, shock, and ECG abnormalities. Monitoring of the serum potassium level is essential because mild hyperkalemia is not usually associated with an abnormal ECG. When abnormal, the ECG in hyperkalemia is characterized primarily by tall, peaked T waves or elevations from previous tracings. There may also be lowering of the R wave and increased depth of the S wave, widening and even disappearance of the P wave, progressive widening of the QRS complex, prolongation of the PR interval, and ST depression. Treatment of hyperkalemia: If hyperkalemia occurs in patients taking amiloride HCl, the drug should be discontinued immediately. If the serum potassium level exceeds 6.5 mEq per liter, active measures should be taken to reduce it. Such measures include the intravenous administration of sodium bicarbonate solution or oral or parenteral glucose with a rapid-acting insulin preparation. If needed, a cation exchange resin such as sodium polystyrene sulfonate may be given orally or by enema. Patients with persistent hyperkalemia may require dialysis. Diabetes Mellitus In diabetic patients, hyperkalemia has been reported with the use of all potassium-conserving diuretics, including amiloride HCl, even in patients without evidence of diabetic nephropathy. Therefore, amiloride HCl should be avoided, if possible, in diabetic patients and, if it is used, serum electrolytes and renal function must be monitored frequently. Amiloride HCl should be discontinued at least 3 days before glucose tolerance testing. Metabolic or Respiratory Acidosis Antikaliuretic therapy should be instituted only with caution in severely ill patients in whom respiratory or metabolic acidosis may occur, such as patients with cardiopulmonary disease or poorly controlled diabetes. If amiloride HCl is given to these patients, frequent monitoring of acid-base balance is necessary. Shifts in acid-base balance alter the ratio of extracellular/intracellular potassium, and the development of acidosis may be associated with rapid increases in serum potassium levels.
ADVERSE REACTIONS Amiloride HCl is usually well tolerated and, except for hyperkalemia (serum potassium levels greater than 5.5 mEq liter - see WARNINGS ), significant adverse effects have been reported infrequently. Minor adverse reactions were reported relatively frequently (about 20%) but the relationship of many of the reports to amiloride HCl is uncertain and the overall frequency was similar in hydrochlorothiazide treated groups. Nausea/anorexia, abdominal pain, flatulence, and mild skin rash have been reported and probably are related to amiloride. Other adverse experiences that have been reported with amiloride are generally those known to be associated with diuresis, or with the underlying disease being treated. The adverse reactions for amiloride HCl listed in the following table have been arranged into two groups: (1) incidence greater than one percent; and (2) incidence one percent or less. The incidence for group (1) was determined from clinical studies conducted in the United States (837 patients treated with amiloride HCl). The adverse effects listed in group (2) include reports from the same clinical studies and voluntary reports since marketing. The probability of a causal relationship exists between amiloride HCl and these adverse reactions, some of which have been reported only rarely. Incidence > 1% Incidence ≤ 1% Body as a Whole Headache* Back pain Weakness Chest pain Fatigability Neck/shoulder ache Pain, extremities Cardiovascular None Angina pectoris Orthostatic hypotension Arrhythmia Palpitation Digestive Nausea/anorexia* Jaundice Diarrhea* GI bleeding Vomiting* Abdominal fullness Abdominal pain GI disturbance Gas pain Thirst Appetite changes Heartburn Constipation Flatulence Dyspepsia Metabolic Elevated serum potassium levels (>5.5 mEq per liter)** None Skin None Skin rash Itching Dryness of mouth Pruritus Alopecia Musculoskeletal Muscle cramps Joint pain Leg ache Nervous Dizziness Paresthesia Encephalopathy Tremors Vertigo Psychiatric None Nervousness Mental confusion Insomnia Decreased libido Depression Somnolence Respiratory Cough Shortness of Breath Dyspnea Special Senses None Visual disturbances Nasal congestion Tinnitus Increased intraocular pressure Urogenital Impotence Polyuria Dysuria Urinary frequency Bladder spasms Gynecomastia *Reactions occurring in 3% to 8% of patients treated with amiloride HCl. (Those reactions occurring in less than 3% of the patients are unmarked.) **See WARNINGS Causal Relationship Unknown Other reactions have been reported but occurred under circumstances where a causal relationship could not be established. However, in these rarely reported events, that possibility cannot be excluded. Therefore, these observations are listed to serve as alerting information to physicians. Activation of probable pre-existing peptic ulcer Aplastic anemia Neutropenia Abnormal liver function To report SUSPECTED ADVERSE REACTIONS contact AvKARE, Inc. at 1-855-361-3993; email drugsafety@avkare.com ; or FDA at 1-800-FDA-1088 or www.fda.gov/medwatch .