Question 1

What is diphenhydramine?

Accepted Answer

Diphenhydramine Hydrochloride Injection, USP is a sterile, nonpyrogenic solution for intravenous or deep intramuscular use as an antihistaminic agent. Each mL contains diphenhydramine hydrochloride 50 mg in Water for Injection. pH 4.0 to 6.5; sodium hydroxide and/or hydrochloric acid added, if needed, for pH adjustment. The chemical name of diphenhydramine hydrochloride is 2-(Diphenylmethoxy)-N,N-dimethylethylamine hydrochloride. The structural formula is as follows: C 17 H 21 NO • HCl MW 291.82 Diphenhydramine hydrochloride occurs as a white crystalline powder and is freely soluble in water and alcohol. structure

Question 2

What kind of drug is diphenhydramine?

Accepted Answer

The FDA classifies diphenhydramine as a histamine-1 receptor antagonist. H1 antihistamines work by blocking histamine, the chemical released during an allergic reaction, from attaching to H1 receptors. This prevents the sneezing, itching, runny nose, watery eyes, and hives that histamine would otherwise trigger. If you are checking whether it is safe to combine with something else, the class is what matters — two drugs from the same class usually should not be stacked.

Question 3

Can you take diphenhydramine with other medicines?

Accepted Answer

It depends on the medicine. We check it against the FDA labels rather than guessing: our interaction checker searches each drug's own label for the other and quotes what it says, naming the section it came from. Run diphenhydramine against whatever else you take — and remember that a label not naming a drug is not the same as that combination being safe.

Question 4

What brand names is diphenhydramine sold under?

Accepted Answer

We track 4 diphenhydramine-containing products in the U.S.: Benadryl, Benadryl Preservative Free, Benylin and Diphenhydramine Hydrochloride. They are the same active ingredient; they differ in form, manufacturer, price and FDA recall record.

Question 5

What forms does diphenhydramine come in?

Accepted Answer

Across the brands we track, diphenhydramine is currently marketed as tablet, kit, injectable, syrup, solution and capsule, per the FDA's National Drug Code Directory. Each form is dosed differently — follow the label for the exact product you were prescribed.

Question 6

Is there a generic diphenhydramine?

Accepted Answer

Yes. Our catalog lists 1 generic diphenhydramine product alongside the brand versions. A generic has the same active ingredient and must meet the FDA's bioequivalence standard; it usually costs less. Ask your pharmacist which one your plan covers.

Question 7

Has diphenhydramine been recalled?

Accepted Answer

The FDA's Enforcement database lists at least 5 recall records whose product description mentions diphenhydramine. The most recent: Unisom, SleepMinis, Diphenhydramine HCl, Mini-Capsules, 25 mg, 60 Mini-Capsules… (Mar 26, 2025). A recall applies to specific lots, not to the drug as a whole — check the record for the affected lot numbers.

#	Drug	Rating	Type	Form	Generic?	Typical price
1	Benadryl	Not yet rated	Prescription	Tablet	Generic	$0	View →
2	Benadryl Preservative Free	Not yet rated	Prescription	Injectable	Generic	$0	View →

Imprint	Strength	Colour	Shape	Maker
S4	25 mg	pink	capsule	—
CPC752	25 mg / 500 mg	blue	oval	—
L050	38 mg / 200 mg	blue	oval	—
DI;200	200 mg / 38 mg	blue	capsule	—
L050	38 mg / 200 mg	blue	oval	—
MOTRIN;PM	200 mg / 38 mg

Diphenhydramine: uses, dosing, side effects & brands

Key facts

How diphenhydramine is dosed

Diphenhydramine side effects

Who shouldn’t take diphenhydramine

Every diphenhydramine product we track (4)

What diphenhydramine pills look like

Combination products containing diphenhydramine

Diphenhydramine recalls

Frequently asked questions

Diphenhydramine drug interactions