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Diphenhydramine Injection


Generic Name: diphenhydramine hydrochloride
Dosage Form: injection, solution

Diphenhydramine Injection Description

Diphenhydramine hydrochloride is an anti­histamine drug having the chemical name 2-(Diphenylmethoxy)-N,N-dimethylethylamine hydrochloride. It occurs as a white, crystalline powder, is freely soluble in water and alcohol.

The structural formula is as follows:

Diphenhydramine hydrochloride  in  the  par­ enteral  form is a sterile,  pyrogen-free solution available in a concentration of 50 mg of diphen­ hydramine hydrochloride per  ml. pH 4.0 to 6.5; sodium hydroxide and/or hydrochloric acid added, if needed, for pH adjustment.

Diphenhydramine Injection - Clinical Pharmacology

Diphenhydramine hydrochloride is an anti­-histamine 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 hydrochloride 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 is not available.

Indications and Usage for Diphenhydramine Injection

Diphenhydramine hydrochloride in the injectable form is effective in adults and pedi­atric patients, other than premature infants and neonates, for the following conditions when diphenhydramine hydrochloride in the oral form is impractical.


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.


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.


Use in Neonates or Premature Infants

This drug should not be 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.


Antihistamines should be used  with consider­able caution in patients with narrow-angle glaucoma, stenosing peptic ulcer, pyloroduo­ denal obstruction, symptomatic prostatic hyper­trophy, or bladder-neck obstruction.

Local necrosis has been associated with the use  of  subcutaneous or  intradermal use  of intravenous diphenhydramine hydrochloride.

Use in Pediatric Patients

In pediatric patients, especially, antihistamines in overdosage may cause hallucinations, con­vulsions, or death.

As in adults, antihistamines may diminish mental alertness in pediatric patients.  In the young pediatric patient, particularly, they may produce excitation.

Use in the  Elderly (approximately 60 years or older)

Antihistamines are more likely to cause  dizzi­ness, sedation, and  hypotension in elderly patients.



Diphenhydramine hydrochloride has  an atropine-like action and,  therefore, should be used  with caution in patients with a history  of bronchial asthma, increased intraocular pres­ sure, hyperthyroidism, cardiovascular disease or hypertension. Use with caution in patients with lower respiratory disease including asthma.

Information for  Patients

Patients taking diphenhydramine hydrochloride should be advised that this drug may cause drowsiness and has an additive effect with alcohol. Patients should be warned about engaging in activites requiring mental alertness such as driving a car  or operating appliances, machinery. etc.

Drug Interactions

Diphenhydramine hydrochloride has additive effects  with  alcohol and  other  CNS  depres­ sants (hypnotics, sedatives, tranquilizers, etc.). MAO inhibitors prolong and intensify the anticholinergic (drying)  effects of  antihista­mines.

Carcinogenesis, Mutagenesis, Impairment of Fertility

Long-term studies in  animals to determine mutagenic and carcinogenic potential have not been performed.


Pregnancy  Category B.Reproduction studies have been performed in rats and rabbits at doses up to 5 times the human dose and have revealed no evidence of impaired fertility or harm to  the fetus due to diphenhydramine hydrochloride. There  are, however, no ade­quate and well-controlled studies in pregnant women. Because animal reproduction studies are not always predictive of human response, this drug should be used during pregnancy only if clearly  needed.

Pediatric Use

Diphenhydramine hydrochloride should not be used  in neonates and premature infants (see CONTRAINDICATIONS).

Diphenhydramine hydrochloride may dimimish mental alertness, or, in the young pediatric patient, cause  excitation. Overdosage may cause hallucinations, convulsions, or death (see WARNINGS and OVERDOSAGE) .


Adverse Reactions

The most frequent adverse reactions are  underscored.

1. General: Urticaria, drug rash, anaphylactic shock, photosensitivity, excessive perspira­tion, chills, dryness of  mouth, nose and throat.

2. Cardiovascular  System:  Hypotension, headache,  palpitations,  tachycardia, extrasystoles.

3. Hematologic System: Hemolytic anemia, thrombocytopenia, agranulocytosis.

4. 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.

5. Gl  System: Epigastric distress, anorexia, nausea, vomiting, diarrhea, constipation.

6. GU System:  Urinary frequency, difficult uri­nation, urinary retention, early menses.

7. Respiratory System:  Thickening of bronchialsecretions, tightness of chest or throat and wheezing, nasal stuffiness.


Antihistamine overdosage reactions may vary from central nervous system depression to stimulation. Stimulation is particularly likely in pediatric patients. Atropine-like signs and symp­toms; dry mouth; fixed, dilated pupils; flushing; and gastrointestinal symptoms may also occur. Stimulants should not be used.

Vasopressors may be used to treat hypoten­sion.

Diphenhydramine Injection Dosage and Administration


Diphenhydramine hydrochloride in the injectable form is indicated when the oral form is impractical.

Parenteral drug products should be inspected visually for particulate matter and discoloration prior to administration, whenever solution and container permit.


Pediatric Patients, other than premature infants and neonates: 5  mg/kg/24 hr or 150 mg/m2/24 hr.  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 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.

How is Diphenhydramine Injection Supplied

It is supplied as a sterile, pyrogen-free solution containing 50 mg diphenhydramine hydrochlo­ ride in each milliliter of solution, and available in packages of 25.

Vial stoppers do  not  contain natural rubber latex.

Store  at 20° to  25°C  (68°  to  7rF) [see  USP Controlled Room Temperature] .

Protect  from freezing and light.

APP Pharmaceuticals, LLC

Schaumburg, IL 60173


Revised: April 2008

diphenhydramine hydrochloride injection, solution
Product Information
Product Type HUMAN PRESCRIPTION DRUG LABEL Item Code (Source) NDC:52584-664(NDC:63323-664)
Route of Administration INTRAVENOUS, INTRAMUSCULAR DEA Schedule     
Active Ingredient/Active Moiety
Ingredient Name Basis of Strength Strength
Inactive Ingredients
Ingredient Name Strength
# Item Code Package Description
1 NDC:52584-664-01 1 VIAL in 1 BAG
1 1 mL in 1 VIAL
Marketing Information
Marketing Category Application Number or Monograph Citation Marketing Start Date Marketing End Date
ANDA ANDA040466 06/13/2017
Labeler - General Injectables and Vaccines, Inc (108250663)
Revised: 06/2017
General Injectables and Vaccines, Inc