Metolazone
ZAROXOLYN
Pronunciation: me-TOL-a-zoen
“Xeroxin’ Me to laser zone”
Bananas dispersing → ↓ serum potassium
What it isNCC-inhibiting thiazide-like diuretic; refractory edema in heart failure and kidney disease.
Why this oneIts pronounced synergy with loop diuretics makes it a rescue for diuretic-resistant edema even at low GFR.
What limits itThe combined diuresis can be profound — check electrolytes and volume within days. It is not interchangeable with other thiazides.
Pearls
- No hypertension outcome data; reserve for edema.
Metolazone prescription history
Animated chart of estimated U.S. prescriptions per year, Diuretics (1953–2026). Metolazone enters in 1973 (estimated).
FDA-approved for
- edema (~1974)
Principal riskProfound diuresis and electrolyte loss when added to a loop diuretic
Sulfonamide
Sulfonamide-derived drug (non-antibacterial) — label warns
No N4 aromatic amine, no N1 heterocycle: cross-reactivity after a sulfonamide-antimicrobial reaction is unlikely — sulfa-allergic patients reacted to sulfonamide non-antibiotics at 9.9% vs 1.6%, less often than to penicillin. The label warns anyway.
Open the sulfonamide hypersensitivity presentation → · sources [n] are on its References slide.
Classes and tags
Clinical profile
Legacy pregnancy categoryC
Defining liabilityVolume depletion and electrolyte disturbances; kidney function and interacting medications modify risk.
FDA label
Read the full label on DailyMed ↗
NO BOXED WARNINGS
| FDA dosing | Population | Start | Target | Max |
|---|---|---|---|---|
| Edema of cardiac failure | Adult | 5–20 mg QD | ||
| Edema of renal disease | Adult | 5–20 mg QD | ||
| Mild–moderate essential hypertension | Adult | 2.5–5 mg QD |
Renal Undefined (contraindicated in anuria)
Hepatic Undefined (contraindicated in hepatic coma/precoma)
Instructions
- Single daily dose; titrate to the minimal effective dose
- Reduce dose once desired therapeutic effect obtained
Available strengths
- tab 2.5, 5, 10 mg
Contraindications
- Anuria
- Hepatic coma or precoma
Cautions
- Electrolyte imbalance: hypokalemia, hyponatremia, hypochloremic alkalosis
- Excessive volume depletion / orthostatic hypotension
- Hyperuricemia (gout), hyperglycemia
- Serious skin reactions (TEN, Stevens-Johnson syndrome)
- Photosensitivity
Adverse reactions
- Orthostatic hypotension
- Volume depletion
- Hypokalemia, hyponatremia
- Hyperuricemia
- Dizziness/lightheadedness
- Headache
- Muscle cramps
Pregnancy Use only if clearly needed; crosses placenta; risk of fetal/neonatal jaundice and thrombocytopenia
Lactation Undefined
Cost
Generic entry2003
Open Metolazone in the interactive console ↗
Memory aids: interaction avatars
Open Metolazone in the interactive console ↗
Self-check
- What combination makes metolazone useful in diuretic-resistant edema?
Combination with a loop diuretic. - How soon should electrolytes and volume be checked after combined metolazone diuresis?
Within days.