Diphenhydramine - Diphenhydramine Hydrochloride injection, Solution prescribing information
INDICATIONS AND USAGE
Diphenhydramine hydrochloride injection, USP is effective in adults and pediatric patients, other than premature infants and neonates, for the following conditions when the oral form is impractical.
Antihistaminic
For amelioration of allergic reactions to blood or plasma, in anaphylaxis as an adjunct to epinephrine and other standard measures after the acute symptoms have been controlled and for other uncomplicated allergic conditions of the immediate type when oral therapy is impossible or contraindicated.
Motion Sickness
For active treatment of motion sickness.
Antiparkinsonism
For use in parkinsonism, when oral therapy is impossible or contraindicated, as follows:
parkinsonism in the elderly who are unable to tolerate more potent agents, mild cases of parkinsonism in other age groups and in other cases of parkinsonism in combination with centrally acting anticholinergic agents.
DOSAGE AND ADMINISTRATION
THIS PRODUCT IS FOR INTRAVENOUS OR INTRAMUSCULAR ADMINISTRATION ONLY.
Diphenhydramine hydrochloride injection, USP is indicated when the oral form is impractical.
DOSAGE SHOULD BE INDIVIDUALIZED ACCORDING TO THE NEEDS AND THE RESPONSE OF THE PATIENT.
Pediatric Patients, Other Than Premature Infants and Neonates
5 mg/kg/24 hours or 150 mg/m 2 /24 hours. Maximum daily dosage is 300 mg. Divide into four doses, administered intravenously at a rate generally not exceeding 25 mg/min, or deep intramuscularly.
Adults
10 mg to 50 mg intravenously at a rate generally not exceeding 25 mg/min, or deep intramuscularly; 100 mg if required; maximum daily dosage is 400 mg.
Parenteral drug products should be inspected visually for particulate matter and discoloration prior to administration, whenever solution and container permit.
CONTRAINDICATIONS
Use in Neonates or Premature Infants
This drug should notbe used in neonates or premature infants.
Use in Nursing Mothers
Because of the higher risk of antihistamines for infants generally, and for neonates and prematures in particular, antihistamine therapy is contraindicated in nursing mothers.
Use as a Local Anesthetic
Because of the risk of local necrosis, this drug should not be used as a local anesthetic.
Antihistamines are also Contraindicated in the Following Conditions
Hypersensitivity to diphenhydramine hydrochloride and other antihistamines of similar chemical structure.
ADVERSE REACTIONS
The most frequent adverse reactions are italicized.
General
Urticaria; drug rash; anaphylactic shock; photosensitivity; excessive perspiration; chills; dryness of mouth, nose and throat.
Cardiovascular System
Hypotension, headache, palpitations, tachycardia, extrasystoles.
Hematologic System
Hemolytic anemia, thrombocytopenia, agranulocytosis.
Nervous System
Sedation, sleepiness, dizziness, disturbed coordination , fatigue, confusion, restlessness, excitation, nervousness, tremor, irritability, insomnia, euphoria, paresthesia, blurred vision, diplopia, vertigo, tinnitus, acute labyrinthitis, neuritis, convulsions.
Gastrointestinal System
Epigastric distress , anorexia, nausea, vomiting, diarrhea, constipation.
Genitourinary System
Urinary frequency, difficult urination, urinary retention, early menses.
Respiratory System
Thickening of bronchial secretions , tightness of chest and wheezing, nasal stuffiness.
To report SUSPECTED ADVERSE REACTIONS, contact Avenacy at 1-855-283-6229 or FDA at 1-800-FDA-1088 or www.fda.gov/medwatch.
Drug Interactions
Diphenhydramine hydrochloride has additive effects with alcohol and other CNS depressants (hypnotics, sedatives, tranquilizers, etc.)
MAO inhibitors prolong and intensify the anticholinergic (drying) effects of antihistamines.
DESCRIPTION
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.
CLINICAL PHARMACOLOGY
Diphenhydramine hydrochloride is an antihistamine with anticholinergic (drying) and sedative side effects. Antihistamines appear to compete with histamine for cell receptor sites on effector cells.
Diphenhydramine hydrochloride in the injectable form has a rapid onset of action.
Diphenhydramine is widely distributed throughout the body, including the CNS. A portion of the drug is excreted unchanged in the urine, while the rest is metabolized via the liver. Detailed information on the pharmacokinetics of diphenhydramine hydrochloride injection, USP is not available.
HOW SUPPLIED
Diphenhydramine Hydrochloride Injection, USP 50 mg per mL is a clear, colorless solution supplied as follows:
| NDC | Diphenhydramine Hydrochloride Injection, USP | Package Factor |
| 83634-781-01 | 50 mg per mL Single-Dose Vial | 25 vials per carton |
Storage Conditions
Store at 20° to 25°C (68° to 77°F); excursions permitted between 15° and 30°C (59° and 86°F). [See USP Controlled Room Temperature.]
Protect from light. Keep covered in carton until time of use.
Discard unused portion.
Sterile, Nonpyrogenic, Preservative-free. The container closure is not made with natural rubber latex.
AVENACY Mfd. for Avenacy Schaumburg, IL 60173 (USA) Made in India ©2025 Avenacy
Revised: May 2025
