Prescription medication · Thiazide-Like Diuretic
metolazone
Also sold as Zaroxolyn. Metolazone treats water retention (edema) caused by heart failure or kidney problems.
Data updated 2026-05-15
- 10,872
- FDA reportsModerately reported
- $0.43
- Generic price (NADAC)
metolazone (Zaroxolyn) is a prescription Thiazide-Like Diuretic. Metolazone treats water retention (edema) caused by heart failure or kidney problems.
Metolazone is a water pill that helps your body get rid of extra salt and water. It can also lower blood pressure.
Verify with FDA → · CMS NADAC pricing →
Drug Pricing (NADAC)
Generic Price
$0.43/unit
Generic Available
Yes (10 manufacturers)
Pricing data from NADAC (CMS), effective December 18, 2024. Compare all drug costs →
What it does
Metolazone treats water retention (edema) caused by heart failure or kidney problems.
Common side effects
Dizziness, Lightheadedness, Drowsiness
Key warnings
If you have trouble urinating, are in a hepatic coma or precoma, or are allergic to metolazone, you should not take this medicine.
The sections below are summarized in plain English from metolazone's FDA-approved prescribing information. They describe what the official label says, and are not personal medical advice.
How It Works
Metolazone is a diuretic, which means it helps your kidneys remove salt and water from your body. This reduces the amount of fluid in your blood vessels, which can lower blood pressure and reduce swelling. It belongs to a class of drugs called thiazide-like diuretics.
How to Take It
Take metolazone once a day. Your doctor will adjust your dose to find what works best for you. It may take a few days to weeks to see the full effect, especially for blood pressure. Follow your doctor's instructions carefully and don't change your dose without talking to them.
This is a plain-language summary of metolazone's FDA labeling, not individualized dosing advice. Ask a pharmacist or prescriber before changing how you take this medication.
Pregnancy & Breastfeeding
Using diuretics during pregnancy can expose the mother and fetus to unnecessary risks. Talk to your doctor about the risks and benefits of taking metolazone while pregnant or breastfeeding. It should only be used if medically necessary.
This is a plain-language summary of metolazone's FDA labeling, not individualized advice. Ask a pharmacist or prescriber about pregnancy or breastfeeding on this medication.
Missed Dose
If you miss a dose, take it as soon as you remember. If it is close to your next dose, skip the missed dose and continue with your regular schedule.
This is a plain-language summary of metolazone's FDA labeling, not individualized advice. Ask a pharmacist or prescriber what to do about your specific missed dose.
Storage
Store metolazone tablets at room temperature (68° to 77°F) and protect them from light. Keep out of the reach of children.
Side Effects (from patient reports)
Based on 10,872 FDA adverse event reports.
Most-reported reactions
Adverse reactions in FAERS for metolazone, by number of reports
- Difficulty breathing
Difficulty breathing
1,204 reports
- Death
Death
868 reports
- Sudden kidney damage
Sudden kidney damage
790 reports
- Feeling sick to your stomach
Feeling sick to your stomach
735 reports
- Kidney failure
Kidney failure
712 reports
- Congestive heart failure
Congestive heart failure
674 reports
- Tiredness
Tiredness
648 reports
- Diarrhea
Diarrhea
639 reports
- Feeling unsteady
Feeling unsteady
599 reports
- Long-term kidney disease
Long-term kidney disease
589 reports
What this shows Bars show how often each reaction was reported, not how likely it is to happen, a report records a temporal association, never proof that the drug caused it.
Reports over time
Adverse-event reports filed for metolazone each year to the FDA Adverse Event Reporting System (FAERS).
Year-to-year volume tracks usage, prescribing, and scrutiny, not a change in per-patient risk. Source: FDA FAERS.
Where metolazone sits
metolazone has more FDA adverse-event reports than 41% of the drugs FAERS tracks. A high position reflects how widely a drug is used and watched, not how dangerous it is.
Percentile across all drugs PlainMeds tracks by FAERS report volume. The dot is metolazone; the line is the median (50th percentile).
FDA Adverse Event Report Analysis
Detailed analysis of 10,872 reports from the FDA Adverse Event Reporting System (FAERS). Reports span 2003–2025.
Total Reports
10,872
Reports Mentioning Death
2,165
19.9% of reports — not proof of cause
Hospitalization Reports
5,657
Top Indication
Product Used For Unknown Indication
Gender Distribution
Age Distribution
Most Reported Adverse Reactions (FAERS)
| # | Reaction | Reports |
|---|---|---|
| 1 | DYSPNOEA | 1,204 |
| 2 | DEATH | 867 |
| 3 | ACUTE KIDNEY INJURY | 790 |
| 4 | NAUSEA | 736 |
| 5 | RENAL FAILURE | 713 |
| 6 | CARDIAC FAILURE CONGESTIVE | 674 |
| 7 | FATIGUE | 648 |
| 8 | DIARRHOEA | 639 |
| 9 | DIZZINESS | 600 |
| 10 | CHRONIC KIDNEY DISEASE | 589 |
| 11 | HYPOTENSION | 579 |
| 12 | ASTHENIA | 572 |
| 13 | HEADACHE | 537 |
| 14 | OEDEMA PERIPHERAL | 524 |
| 15 | FALL | 507 |
Reactions in Death Reports
Reactions in Hospitalization Reports
Source: FDA FAERS (Adverse Event Reporting System) FDA FAERS (Adverse Event Reporting System) Reports are voluntary and do not establish causation
Serious Warnings
If you have trouble urinating, are in a hepatic coma or precoma, or are allergic to metolazone, you should not take this medicine. Using diuretics when pregnant can be dangerous to the baby. Only use this medicine during pregnancy if absolutely necessary for a medical condition.
Common Questions
Can I take metolazone if I'm pregnant?
What should I do if I feel dizzy after taking metolazone?
How long does it take for metolazone to start working?
Can I drink alcohol while taking metolazone?
What if I miss a dose?
Does metolazone interact with other medications?
Can metolazone cause dehydration?
How often will I need blood tests?
Can I stop taking metolazone suddenly?
What are the ingredients in metolazone tablets?
What are the common side effects of metolazone?
What drug class is metolazone?
Is metolazone safe during pregnancy?
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What the FDA Data Shows for metolazone
The FDA label for metolazone (sold under brand names such as Zaroxolyn) classifies it as a prescription-only medication in the Thiazide-Like Diuretic class. Metolazone treats water retention (edema) caused by heart failure or kidney problems. Official labeling lists 7 commonly reported side effects, including Dizziness, Lightheadedness, Drowsiness.
Post-market surveillance from the FDA Adverse Event Reporting System (FAERS) captures real-world experience. For this drug, FAERS contains 10,872 voluntary reports. Interaction data is drawn directly from FDA-approved prescribing information. NADAC pricing from CMS shows a generic unit cost of $0.43.
Report counts do not establish causation, a FAERS entry documents a temporal association, not proof that the drug produced the outcome. Widely prescribed medications naturally accumulate more reports than niche therapies, so raw totals must be interpreted alongside total exposure. Shortage status, recall history, and patent information further shape supply and switching decisions. This page summarizes public FDA data for educational purposes only and is not a substitute for professional medical advice, always consult a licensed healthcare provider before starting, stopping, or changing any medication.
Data Sources
Drug labeling: FDA Drug Labels (SPL/DailyMed). Adverse events: FDA Adverse Event Reporting System (FAERS). Pricing: CMS National Average Drug Acquisition Cost (NADAC).
FAERS reports are voluntary and do not establish causation. Drug interactions are derived from FDA labeling and clinical references. Always consult a healthcare professional before making medication decisions.
Last updated: December 24, 2024
Read our methodology - how this data is sourced, computed, and verified.
Data currency: FDA FAERS adverse-event reports through 2025, CMS NADAC acquisition-cost pricing effective December 2024, compiled and last refreshed May 2026. See our methodology for per-source dates and refresh cadence. Spot a figure that looks wrong? Report a correction.
All federal data sources used on this page
- FDA Orange Book - approved drug products with therapeutic equivalence. accessdata.fda.gov/cder/ob
- FDA DailyMed - NIH-hosted drug labeling for FDA-approved meds. dailymed.nlm.nih.gov
- FDA Adverse Event Reporting System (FAERS) - post-marketing safety surveillance. fda.gov/drugs/faers
- NLM RxNorm - standardized clinical drug nomenclature. nlm.nih.gov/research/umls/rxnorm
- CMS Medicare Part B Drug Average Sales Price Files - federal drug pricing data. cms.gov/medicare/part-b-drugs/asp
- FDA Drug Shortages Database - current and resolved drug shortage tracking. accessdata.fda.gov/drugshortages