chlorpheniramine
Brand names: Chlor-Trimeton
Chlorpheniramine is an antihistamine medicine. It helps relieve allergy symptoms.
What it does
This medicine temporarily relieves symptoms from allergies or a cold.
Common side effects
Dizziness, Constipation
Key warnings
There are no boxed warnings for this medication.
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.
How to Take It
Adults and children 12 and over can take 1 tablet every 4 to 6 hours. Do not take more than 6 tablets (24 mg) in 24 hours. Follow your doctor's directions. Children under 12 should ask a doctor.
Pregnancy & Breastfeeding
If you are pregnant or breastfeeding, talk to your doctor before using this medicine. They can advise you on whether it is safe for you and your baby.
Missed Dose
If you miss a dose, take it as soon as you remember. Space it evenly with your other doses.
Storage
Store at room temperature away from moisture and heat.
Side Effects (from patient reports)
Based on 4,153 FDA adverse event reports.
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
Death-Related Reports
1,084
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 |
| 3 | OFF LABEL USE | 506 |
| 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 |
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
There are no boxed warnings for this medication.
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; gastrointestinal...
Mechanism: These drugs can both cause sleepiness and may lower your blood pressure, making you feel more dizzy or lightheaded.
What to do: Be careful when performing activities that require you to be alert, such as driving, until you see how you react.
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?
Is chlorpheniramine safe during pregnancy?
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 →
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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 4,153 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 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).
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: November 13, 2025
Read our methodology — how this data is sourced, computed, and verified.
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