Dosing and uses of Midamor (amiloride)
Adult dosage forms and strengths
tablet
- 5mg
Congestive Heart Failure
5-10 mg/day PO qDay OR divided q12hr
Hypertension
5-10 mg/day PO qDay OR divided q12hr
Thiazide-Induced Hypokalemia
5-10 mg/day PO qDay OR divided q12hr
Renal Impairment
CrCl 10-50 mL/minute: 50% normal dose
CrCl <10 mL/minute: Not recommended
Overdose Management
May use normal saline for volume replacement
May use dopamine or norepinephrine to treat hypotension
Treat hyperkalemia with IV glucose (dextrose 25% in water) with rapid acting insulin with concurrent IV sodium bicarbonate and use oral or rectal solutions of kayexalate in sorbitol if needed
If dysrhythmia due to decreased K+ or Mg+ suspected replace aggressively
Discontinue treatment if no symptoms after 6hr
Other Information
Take with food
Monitor: Serum potassium
See also combo with hydrochlorothiazide
Other Indications & Uses
Off-label: cystic fibrosis, Li-induced polyuria
Pediatric dosage forms and strengths
tablet
- 5mg
Hypertension (Off-label)
0.4-0.625 mg/kg/day PO; not to exceed 20 mg/day
Geriatric dosage forms and strengths
5-10 mg/day PO qDay OR every other day
Maximum dosage limit: 20 mg PO qDay; 40 mg PO qDay has been used
Elderly patients may be more sensitive to the diuretic effects of the drug and are more likely to have age-associated renal dysfunction
Midamor (amiloride) adverse (side) effects
1-10%
Hyperkalemia (10%)
Anorexia (3-8%)
Diarrhea (3-8%)
Headache (3-8%)
Nausea (3-8%)
Vomiting (3-8%)
Abdominal pain (<3%)
Appetite changes (<3%)
Constipation (<3%)
Cough (<3%)
Dizziness (<3%)
Dyspnea (<3%)
Encephalopathy (<3%)
Fatigue (<3%)
Gas pain (<3%)
Impotence (<3%)
Muscle cramps (<3%)
Weakness (<3%)
Warnings
Black box warnings
Like other potassium-conserving agents, amiloride may cause hyperkalemia (serum potassium levels greater than 5.5 mEq/L), which, if not corrected, 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 elderly persons.
When amiloride is used concomitantly with a thiazide diuretic in patients without these complications, the risk of hyperkalemia is reduced to about 1-2%. Monitoring serum potassium levels carefully in any patient receiving amiloride is essential, particularly when it is first introduced, at the time of diuretic dosage adjustments, and during any illness that could affect renal function.
Contraindications
Hypersensitivity to amiloride
Hyperkalemia (K+ >5.5 mEq/L [5.5 mmol/L])
Concomitant use with K+-sparing diuretic, or K supplementation
Impaired renal function (Scr >1.5 mg/dL [132.6 umol/L], or BUN >30 mg/dL [10.7 mmol/L]) diabetes
Cautions
Anuria, DM, diabetic nephropathy, electrolyte imbalance and increases BUN, metabolic or respiratory acidosis
Pregnancy and lactation
Pregnancy category: B
Lactation: excretion in milk unknown/not recommended
Pregnancy categories
A: Generally acceptable. Controlled studies in pregnant women show no evidence of fetal risk.
B: May be acceptable. Either animal studies show no risk but human studies not available or animal studies showed minor risks and human studies done and showed no risk.
C: Use with caution if benefits outweigh risks. Animal studies show risk and human studies not available or neither animal nor human studies done.
D: Use in LIFE-THREATENING emergencies when no safer drug available. Positive evidence of human fetal risk.
X: Do not use in pregnancy. Risks involved outweigh potential benefits. Safer alternatives exist.
NA: Information not available.
Pharmacology of Midamor (amiloride)
Mechanism of action
Direct effect on renal distal convoluted tubule to inhibit Na+ reabsorption from the lumen
Inhibits Na/K-ATPase, decreases Ca++, Mg++ and hydrogen excretion
Pharmacokinetics
Half-Life: 6-9 hr
Duration: 24 hr
Onset: initial effect: 2-3 hr, max effect: 6-10 hr
Peak Plasma Time: 3-4 hr
Bioavailability: 30-90%
Protein Bound: 23%
Vd: 350-380 L
Metabolism: NOT metabolized in the liver; no active metabolites
Excretion
- Urine: 50%
- Feces: 40-50%
