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chlorthalidone

Sold as Thalitone, Hemiclor. Class: Sulfonamides, plain. First FDA approval 04/07/1960: 66 years on the US market.

This grade answers one narrow question: how strong is the public evidence and safety record behind this drug, and how clean is its money trail and court record? It is not a verdict on whether the drug is right for you.

B

Score breakdown (87/100)

Safety ×35%
A
Evidence ×25%
D
Regulatory ×15%
A
Money & lawsuits ×15%
A
Options ×10%
A

Safety: 100

Evidence: 51

Regulatory history: 94

Money & lawsuits: 100

Options: 100

What the FDA label says

Approved uses

is a thiazide-like diuretic indicated: • For the treatment of hypertension, to lower blood pressure. Lowering blood pressure reduces the risk of fatal and nonfatal cardiovascular events, primarily strokes and myocardial infarctions (1.1). • as adjunctive therapy in edema associated with heart failure, cirrhosis of the liver, and renal disease, including nephrotic syndrome (1.2). 1.1 Hypertension THALITONE ® is indicated for the treatment of hypertension, to lower blood pressure. Lowering blood pressure reduces the risk of fatal and nonfatal cardiovascular events, primarily strokes and myocardial infarctions. These benefits have been seen in controlled trials of antihypertensive drugs from a wide variety of pharmacologic classes including the class to which this drug principally belongs. There are no controlled trials demonstrating risk reduction with THALITONE. Control of high blood pressure should be part of comprehensive cardiovascular risk management, including, as appropriate, lipid control, diabetes management, antithrombotic therapy, smoking cessation, exercise, and limited sodium intake. Many patients will require more than one drug to achieve blood pressure goals. For speci...

Contraindications

is contraindicated in patients with anuria or hypersensitivity to chlorthalidone or other sulfonamide-derived drugs. • Anuria (4). • Hypersensitivity (4).

Warnings and precautions

• Hypotension: Higher risk for patients with impaired sympathetic response, volume-depletion or salt restriction (5.1). • Renal Impairment: Patients with pre-existing kidney disease may be at higher risk. (5.2). • Monitor serum electrolytes periodically (5.3). 5.1 Hypotension THALITONE may cause symptomatic hypotension. Patients with impaired sympathetic response, volume-depletion or who are salt restricted may be at increased risk for developing hypotension. If hypotension occurs, place the patient in the supine position and, if necessary, give intravenous normal saline. A transient hypotensive response is not a contraindication to further treatment, which usually can be continued without difficulty once the blood pressure has stabilized. 5.2 Impaired Renal Function Changes in renal function including acute renal failure can be caused by diuretics. Patients with chronic kidney disease, heart failure, or volume depletion may be at particular risk of developing acute renal failure on THALITONE. Monitor renal function periodically. Consider withholding or discontinuing therapy in patients who develop a clinically significant decrease in renal function on THALITONE [see Drug Interacti...

Adverse reactions (label)

The following adverse reactions are described in more detail elsewhere in the label; • Hypotension [see Warnings and Precautions (5.1)] • Impaired Renal Function [see Warnings and Precautions (5.2)] • Electrolyte Abnormalities [see Warnings and Precautions (5.3)] • Metabolic Disturbances [see Warnings and Precautions (5.4)] The following adverse reactions have been observed, but there is not enough systematic collection of data to support an estimate of their frequency. Gastrointestinal System Reactions: anorexia, gastric irritation, nausea, vomiting, cramping, diarrhea, constipation, jaundice (intrahepatic cholestatic jaundice), pancreatitis. Central Nervous System Reactions : dizziness, paresthesias, headache. Hematologic Reactions: leukopenia, agranulocytosis, thrombocytopenia, aplastic anemia. Dermatologic-Hypersensitivity Reactions: purpura, photosensitivity, rash, urticaria, necrotizing angiitis (vasculitis) (cutaneous vasculitis), Lyell’s syndrome (toxic epidermal necrolysis). Cardiovascular Reaction: Orthostatic hypotension. Other Adverse Reactions: muscle spasm, weakness, restlessness, impotence, xanthopsia. The most frequently expected adverse drug reactions among patient...

Source: FDA SPL label for Thalitone (Casper Pharma LLC), effective 20260625. Full label on DailyMed.

Side-effect reports sent to the FDA

These are counts of reports people filed, not rates of harm. Anyone can file one, and nobody checks whether the drug was the cause. Millions of doses are taken for every report sent, so the useful part is how this drug compares with the average across all drugs.

12,351reports that mention this drug
12,268of those blame this drug, not another one the person was taking
65%of reports describe a serious outcome, such as a hospital stay (average for all drugs: 57%)
5.9%of reports include a death, from any cause (average for all drugs: 9.1%)

Problems reported most often

Fatigue · 931Nausea · 792Drug Ineffective · 769Diarrhoea · 751Dizziness · 629Off Label Use · 588Headache · 581Pain · 570Dyspnoea · 563Acute Kidney Injury · 552Chronic Kidney Disease · 548Arthralgia · 470Asthenia · 467Hypertension · 446Vomiting · 435

Reports per year

20192020202120222023202420252026
1,2631,2051,2061,1281,0601,0991,169502

927 reports blaming this drug for every million Medicare prescriptions filled, which is 0.3× the typical drug on this site. (2,729 reports in 2024–2026, against 2,944,741 Medicare fills in one year. This is the one number here that accounts for how many people take the drug.)

Source: the FDA's Adverse Event Reporting System (FAERS). Reports are voluntary and unverified. Drugs that are prescribed a lot, in the news, or in lawsuits attract more reports, so the percentages are compared with the whole database to correct for that partly, not fully.

Recalls and regulatory record

5recall actions on file
3 / 47brand / generic applications
0label changes since 2021
NoREMS program
DateClassFirmReason
09/2026Class IIInventia Healthcare LimitedFailed Dissolution Specifications
06/2026Class IIInventia Healthcare LimitedFailed Dissolution Specifications
05/2025Class IIAvKAREFailed Dissolution Specifications
02/2022Class IISUN PHARMACEUTICAL INDUSTRIES INCForeign Matter identified as stainless steel microscopic wear particles mixed with punch lubricant oil and silicone particles from the dust cup
01/2022Class IICARDINAL HEALTHCARECGMP Deviations: Products were exposed to temperatures outside of the products labeled storage conditions.

Class I = reasonable probability of serious harm. Class II = temporary or reversible harm. Class III = unlikely to harm. Most generic recalls are manufacturing or labeling defects for one lot, not a verdict on the molecule.

Evidence base

128randomized trials (PubMed)
13systematic reviews
109registered trials
42%of completed trials posted results
15%terminated or withdrawn
40%industry-funded

Counts measure how much evidence exists and how transparent it is, not how big the benefit is. For that, ask your prescriber: if 100 people like me took this, how many would get better because of it, and how many would be harmed? (Doctors call these the "number needed to treat" and "number needed to harm.") It differs by condition and is the number drug ads leave out. Sources: PubMed, ClinicalTrials.gov.

Money and lawsuits

In 2024, drug companies reported $0 in payments to US physicians and hospitals tied to this drug across 0 transactions.

No pending federal MDL names this drug or its brands.

Not named in any federal pharmaceutical settlement of $100M or more on record.

Sources: CMS Open Payments (Sunshine Act); Judicial Panel on Multidistrict Litigation pending docket list; DOJ settlements as tabulated on Wikipedia with links to the primary record. State-court and individual suits are not included.

Who takes it and what it costs

815,578Medicare Part D patients (2024)
2,944,741prescriptions filled
$17average cost per fill
$49Mtotal Medicare spend
ProductFills$/fill
Chlorthalidone2,941,224$16
Thalitone3,517$164

Same-class alternatives

clopamideindapamidemefrusidequinethazonexipamide

Same ATC pharmacological class, graded ones first, best grade at the top. Being in the same class does not make them interchangeable for your condition; it makes them worth asking about.

Questions to ask your prescriber

  1. The most-reported problems in FDA's adverse event data are fatigue, nausea, diarrhoea. How would we recognize and handle those?
  2. Off-label use is among the most-reported items for this drug. Is my use on-label, and if not, what evidence supports it?
  3. Why this one over clopamide, indapamide, mefruside? What would make you pick one of those instead?
  4. What result are we expecting, by when, and what is the plan if it does not happen?
  5. If 100 people like me took this drug, how many would actually get better because of it, and how many would be harmed by it? (Doctors call these the number needed to treat and the number needed to harm.)