chlorpheniramine vs diphenhydramine
Side-by-side comparison of chlorpheniramine and diphenhydramine Data from FDA drug databases (Orange Book, NDC Directory, recalls, shortages) covering 20,000+ approved drugs, plus CMS pricing; see our methodology.
Chlor-Trimeton
Benadryl
Chlorpheniramine is an antihistamine medicine. It helps relieve allergy symptoms.
Diphenhydramine, also known as Benadryl, is an antihistamine medicine. It helps relieve allergy and cold symptoms.
This medicine temporarily relieves symptoms from allergies or a cold. It can help with sneezing, runny nose, and itchy eyes. It also helps with itching of the nose or throat.
This medicine temporarily relieves symptoms from allergies or hay fever. These symptoms include sneezing, itchy nose or throat, runny nose, and itchy, watery eyes. It also helps with sneezing and runny nose caused by the common cold.
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.
Diphenhydramine blocks histamine, a natural substance that your body makes during an allergic reaction. By blocking histamine, it reduces allergy symptoms. It can also dry up nasal passages to relieve a runny nose.
- • Dizziness
- • Constipation
- • Headache
- • Fatigue
- • Nausea
- Feeling sick to your stomach 601
- Loose stools 568
- Using the medicine for something it's not approved for 506
- Feeling tired 467
- Difficulty breathing 416
- Using the medicine for a purpose it's not approved for 7,772
- Headache 5,138
- Tiredness 5,076
- Feeling sick to your stomach 4,484
- Pain 4,014
There are no boxed warnings for this medication.
There are no boxed warnings for this medication.
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.
If you are pregnant or breastfeeding, talk to your doctor before using this medicine. It is important to weigh the benefits and risks with your doctor.
How to Read This chlorpheniramine vs diphenhydramine Comparison
chlorpheniramine is classified in the First-Generation Antihistamine drug class, while diphenhydramine sits within the First-Generation Antihistamine class. Because both drugs share the same classification, they are often considered interchangeable in theory — but clinical outcomes rarely track that cleanly. Both drugs are available over the counter.
Adverse event totals above are pulled from the FDA's Adverse Event Reporting System (FAERS). For these top-ranked reactions alone, chlorpheniramine has 2,558 submissions while diphenhydramine has 26,484. Those figures reflect cumulative reporting volume — not per-patient risk — so older, widely dispensed drugs typically look worse on count alone. No direct interaction between these two drugs is listed in our FDA-derived dataset, though co-prescription still warrants pharmacist review. Serious warnings, pregnancy guidance, and contraindications can differ even when indications overlap.
A table cannot substitute for clinical judgment. Effectiveness, tolerability, drug-drug interactions with your other medications, kidney and liver function, pregnancy status, insurance formulary, and price all feed into a decision that only a licensed prescriber can make responsibly. Data here is sourced from FDA Structured Product Labels (SPL) and FAERS, both of which update as manufacturers and clinicians submit new information. This page is for educational purposes only, is not medical advice, and should not be used to self-switch between chlorpheniramine and diphenhydramine — always consult your physician or pharmacist first.
Important: This comparison is for informational purposes only. Drug effects vary between individuals. Always consult your doctor or pharmacist for personalized medical advice.