amiloride
Brand: Midamor
Prototype: spironolactone
Drug Class: potassium-sparing diuretic
Drug Family: diuretic
Subclass: pyrazine-carbonyl guanidine ENaC blocker
Organ Systems: renalcardiovascular
Mechanism of Action
Directly blocks ENaC in collecting duct; mild natriuresis with potassium retention; also used for lithium-induced nephrogenic DI.
epithelial sodium channel (ENaC) in collecting duct
Indications
- edema (with thiazide/loop)
- hypokalemia prevention
- lithium-induced nephrogenic diabetes insipidus (off-label)
Contraindications
- hyperkalemia
- severe renal impairment
Adverse Effects
Common
- hyperkalemia
- nausea
- diarrhea
- headache
Serious
- severe hyperkalemia
Pharmacokinetics (ADME)
| Absorption | 15-25% oral |
| Distribution | moderate |
| Metabolism | minimal hepatic — excreted largely unchanged |
| Excretion | renal |
| Half-life | 6-9 hours |
| Onset | 1-4 hours |
| Peak | 6-10 hours |
| Duration | 24 hours |
| Protein Binding | <23% |
| Vd | moderate |
Drug Interactions
| Drug / Agent | Mechanism | Severity |
|---|---|---|
| ACE inhibitors/ARBs | additive hyperkalemia | major |
| NSAIDs | reduced efficacy | moderate |
Nursing Considerations
- K+ monitoring essential
- Useful in lithium-induced nephrogenic DI (blocks ENaC through which lithium enters principal cells)
- Low protein binding — not displaced by other drugs
Clinical Pearls
- Blocks the channel through which lithium enters renal collecting duct cells — reduces lithium-induced nephrogenic DI
- Minimal protein binding — few displacement interactions
Safety Profile
Pregnancy use-with-caution
Lactation use-with-caution
Renal Adjustment Required
Hepatic Adjustment Not required
TDM Not required
Concordance Terms
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