Over-the-counter medication · First-Generation Antihistamine
chlorpheniramine
Also sold as Chlor-Trimeton. This medicine temporarily relieves symptoms from allergies or a cold.
Data updated 2026-05-15
- 6,221
- FDA reportsLightly reported
- 1
- InteractionFew interactions
- OTC
- Availability
What the data shows
chlorpheniramine (Chlor-Trimeton) is an over-the-counter First-Generation Antihistamine, reported less often than most tracked drugs (6,221 FDA reports), with 1 documented drug interaction.
Reporting volume reflects how widely a drug is used and studied, not how dangerous it is, a FAERS report documents a temporal association, never proof of cause.
chlorpheniramine (Chlor-Trimeton) is an over-the-counter First-Generation Antihistamine. This medicine temporarily relieves symptoms from allergies or a cold.
Chlorpheniramine is an antihistamine medicine. It helps relieve allergy symptoms.
Verify with FDA → · CMS NADAC pricing →
What it does
This medicine temporarily relieves symptoms from allergies or a cold.
Common side effects
Dizziness, Constipation
Key warnings
No specific warnings noted. Always follow your prescriber's instructions.
The sections below are summarized in plain English from chlorpheniramine's FDA-approved prescribing information. They describe what the official label says, and are not personal medical advice.
How It Works
Chlorpheniramine blocks histamine, a natural substance your body makes during an allergic reaction. By blocking histamine, it reduces allergy symptoms. This medicine is a first-generation antihistamine.
Side Effects (from patient reports)
Based on 6,221 FDA adverse event reports.
Most-reported reactions
Adverse reactions in FAERS for chlorpheniramine, by number of reports
- Nausea
Nausea
601 reports
- Diarrhoea
Diarrhoea
568 reports
- Fatigue
Fatigue
467 reports
- Dyspnoea
Dyspnoea
416 reports
- Pyrexia
Pyrexia
383 reports
- Vomiting
Vomiting
375 reports
- Neutropenia
Neutropenia
292 reports
- Headache
Headache
274 reports
- Pneumonia
Pneumonia
270 reports
- Cough
Cough
259 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 chlorpheniramine 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 chlorpheniramine sits
chlorpheniramine has more FDA adverse-event reports than 28% 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 chlorpheniramine; the line is the median (50th percentile).
FDA Adverse Event Report Analysis
Detailed analysis of 6,221 reports from the FDA Adverse Event Reporting System (FAERS). Reports span 2004–2025.
Total Reports
6,221
Reports Mentioning Death
1,084
17.4% of reports — not proof of cause
Hospitalization Reports
2,771
Top Indication
Product Used For Unknown Indication
Gender Distribution
Age Distribution
Most Reported Adverse Reactions (FAERS)
| # | Reaction | Reports |
|---|---|---|
| 1 | NAUSEA | 601 |
| 2 | DIARRHOEA | 568 |
| 4 | FATIGUE | 467 |
| 5 | DYSPNOEA | 416 |
| 6 | PYREXIA | 383 |
| 7 | VOMITING | 375 |
| 8 | NEUTROPENIA | 292 |
| 9 | HEADACHE | 274 |
| 10 | PNEUMONIA | 270 |
| 11 | COUGH | 259 |
| 12 | NEUROPATHY PERIPHERAL | 256 |
| 13 | RASH | 254 |
| 14 | PRURITUS | 246 |
| 15 | DEATH | 241 |
| 16 | DIZZINESS | 238 |
Reactions in Death Reports
Reactions in Hospitalization Reports
Source: FDA FAERS (Adverse Event Reporting System) Reports are voluntary and do not establish causation
Known Drug Interactions
Terazosin has been used concomitantly in at least 50 patients on the following drugs or drug classes: analgesic/anti-inflammatory (e.g., acetaminophen, aspirin, codeine, ibuprofen, indomethacin); antibiotics (e.g., erythromycin, trimethoprim and sulfamethoxazole); anticholinergic/sympathomimetics (e.g., phenylephrine hydrochloride, phenylpropanolamine hydrochloride, pseudoephedrine hydrochloride); antigout (e.g., allopurinol); antihistamines (e.g., chlorpheniramine); cardiovascular agents (e.g., atenolol, hydrochlorothiazide, methyclothiazide, propranolol); corticosteroids;...
Mechanism: These drugs can both cause sleepiness and may lower your blood pressure, making you feel more dizzy or lightheaded.
This is a plain-language summary of FDA-label interaction records and does not provide individual medication-combination directions.
Common Questions
What is the most important thing to know about chlorpheniramine?
Can children take chlorpheniramine?
Can I take chlorpheniramine with other medicines?
Will chlorpheniramine make me sleepy?
How often can I take chlorpheniramine?
Can I drive after taking chlorpheniramine?
What should I do if I take too much?
Can I drink alcohol while taking chlorpheniramine?
Does chlorpheniramine interact with any foods?
How long does it take for chlorpheniramine to work?
What are the common side effects of chlorpheniramine?
Does chlorpheniramine interact with other medications?
What drug class is chlorpheniramine?
What pregnancy or breastfeeding source fields are listed for chlorpheniramine?
Related Medications in First-Generation Antihistamine
Other drugs grouped near chlorpheniramine - same-class peers and common alternatives.
azelastine
Astelin, Astepro
Azelastine nasal spray is an antihistamine medicine.
Compare with chlorpheniramine →
budesonide nasal
Rhinocort
Rhinocort is a nasal spray that helps relieve allergy symptoms.
Compare with chlorpheniramine →
cetirizine
Zyrtec
Cetirizine (Zyrtec) is an antihistamine medicine.
Compare with chlorpheniramine →
ciclesonide nasal
Omnaris, Zetonna
Omnaris Nasal Spray is a medicine that helps treat allergy symptoms in your nose.
Compare with chlorpheniramine →
desloratadine
Clarinex
Desloratadine is an antihistamine medicine.
Compare with chlorpheniramine →
Compare beyond drug class
Nationwide peers by FAERS volume & death-report share
Two PlainMeds-derived comparison paths for chlorpheniramine: nearest FDA FAERS report volume and nearest death-report share among drugs with at least 1,000 logged reports, excluding same-class neighbors listed above. Counts reflect reporting volume, not proven individual harm.
Similar FAERS report volume
Nearest drugs by total FAERS reports. This record: 6,221.
- piroxicam Δ 45 reports · Nonsteroidal Anti-Inflammatory Drug (NSAID) 6,176reports
- nabumetone Δ 98 reports · Nonsteroidal Anti-Inflammatory Drug (NSAID) 6,319reports
- tolterodine Δ 102 reports · Anticholinergic (Overactive Bladder) 6,323reports
- phentermine Δ 112 reports · Sympathomimetic Amine (Appetite Suppressant) 6,109reports
Similar death-report share
Nearest drugs by FAERS death-report share. This record: 17.42%.
- valganciclovir Δ 0.07 pts · 18,056 reports · Antiviral (Nucleoside Analog) 17.35%death share
- bisacodyl Δ 0.08 pts · 13,500 reports · Stimulant Laxative 17.50%death share
- amiodarone Δ 0.14 pts · 10,687 reports · Class III Antiarrhythmic 17.28%death share
- lactulose Δ 0.16 pts · 37,033 reports · Osmotic Laxative 17.58%death share
Medication Guides
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Narrow Therapeutic Index Drugs
FDA bioequivalence and label-record context for narrow therapeutic index medicines
Common Drug Interactions
Dangerous medication combinations and how to protect yourself
What the FDA Data Shows for chlorpheniramine
The FDA label for chlorpheniramine (sold under brand names such as Chlor-Trimeton) classifies it as an over-the-counter product in the First-Generation Antihistamine class. This medicine temporarily relieves symptoms from allergies or a cold. Official labeling lists 2 commonly reported side effects, including Dizziness, Constipation.
Post-market surveillance from the FDA Adverse Event Reporting System (FAERS) captures real-world experience. For this drug, FAERS contains 6,221 voluntary reports. The database also lists 1 documented drug interaction derived from FDA labeling, with the top-flagged interaction rated minor severity. Acquisition-cost data is surveyed weekly by CMS and updated as manufacturers report changes.
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 are separate source-record fields. This page is a public FDA/CMS registry and does not provide medical, treatment, substitution, or medication-change directions.
Data Sources
Drug labeling: FDA Drug Labels (SPL/DailyMed). Adverse events: FDA Adverse Event Reporting System (FAERS).
FAERS reports are voluntary and do not establish causation. Drug interactions are derived from FDA labeling and clinical references. This registry does not provide medication decisions.
Last updated: November 13, 2025
PlainMeds is rendered directly from FDA openFDA/FAERS extracts, DailyMed labels, and CMS drug-pricing files, no number is typed in by an editor. FAERS counts, recalls, shortages, and price figures on this page are queried live from those federal extracts. See our editorial standards & corrections policy, the methodology behind these numbers, or report a data error. Data current as of 2026-05-15. Primary sources: openFDA / FAERS, DailyMed and CMS Part B ASP.
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 from the source snapshot dated . See our methodology for per-source dates and refresh cadence. Spot a figure that looks wrong? Report a data issue.
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