Diphenhydramine (Injection)

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# Overview
Diphenhydramine (Injection) is an analgesic and antihistamine that is FDA approved for the treatment of allergic reactions to blood or plasma, uncomplicated allergic conditions of the immediate type, in anaphylaxis as an adjunct to epinephrine, motion sickness and parkinsonism.   Common adverse reactions include xerostomia, dizziness, dyskinesia, sedation, somnolence, dryness of nasal mucosa, pharyngeal dryness, thick sputum.

# Adult Indications and Dosage

## FDA-Labeled Indications and Dosage (Adult)
- Diphenhydramine hydrochloride injection, USP 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.
- 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 combinations with centrally acting anticholinergic agents.

### Dosing Information
- THIS PRODUCT IS FOR INTRAVENOUS OR INTRAMUSCULAR ADMINISTRATION ONLY.
- Diphenhydramine hydrochloride injection, USP 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.
- DOSAGE SHOULD BE INDIVIDUALIZED ACCORDING TO THE NEEDS AND THE RESPONSE OF THE PATIENT.
8 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.

## Off-Label Use and Dosage (Adult)

### Guideline-Supported Use
There is limited information regarding Off-Label Guideline-Supported Use of Diphenhydramine (Injection) in adult patients.

### NonGuideline-Supported Use
There is limited information regarding Off-Label NonGuideline-Supported Use of Diphenhydramine (Injection) in adult patients.

# Pediatric Indications and Dosage

## FDA-Labeled Indications and Dosage (Pediatric)

### Dosing Information
8 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.

## Off-Label Use and Dosage (Pediatric)

### Guideline-Supported Use
There is limited information regarding Off-Label Guideline-Supported Use of Diphenhydramine (Injection) in pediatric patients.

### NonGuideline-Supported Use
There is limited information regarding Off-Label NonGuideline-Supported Use of Diphenhydramine (Injection) in pediatric patients.

# Contraindications
- This drug should not be used in neonates or premature infants.
- Because of the higher risk of antihistamines for infants generally, and for neonates and prematures in particular, antihistamine therapy is contraindicated in nursing mothers.
- Because of the risk of local necrosis, this drug should not be used as a local anesthetic.
- Hypersensitivity to diphenhydramine hydrochloride and other antihistamines of similar chemical structure.

# Warnings
- Antihistamines should be used with considerable caution in patients with narrow-angle glaucoma, stenosing peptic ulcer, pyloroduodenal 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.
- 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.
- Antihistamines are more likely to cause dizziness, sedation, and hypotension in elderly patients.

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

# Adverse Reactions

## Clinical Trials Experience
- The most frequent adverse reactions are underscored.
- Urticaria, drug rash, anaphylactic shock, photosensitivity, excessive perspiration, chills, dryness of mouth, nose, and throat
- Hypotension, headache, palpitations, tachycardia, extrasystoles
- Hemolytic anemia, thrombocytopenia, agranulocytosis
- Sedation, sleepiness, dizziness, disturbed coordination, fatigue, confusion, restlessness, excitation, nervousness, tremor, irritability, insomnia, euphoria, paresthesia, blurred vision, diplopia, vertigo, tinnitus, acute labyrinthitis, neuritis, convulsions
- Epigastric distress, anorexia, nausea, vomiting, diarrhea, constipation
- Urinary frequency, difficult urination, urinary retention, early menses
- Thickening of bronchial secretions, tightness of chest or throat and wheezing, nasal stuffiness

## Postmarketing Experience
There is limited information regarding Diphenhydramine (Injection) Postmarketing Experience in the drug label.

# 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.

# Use in Specific Populations

### Pregnancy
Pregnancy Category (FDA): 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.
Pregnancy Category (AUS): 
There is no Australian Drug Evaluation Committee (ADEC) guidance on usage of Diphenhydramine (Injection) in women who are pregnant.

### Labor and Delivery
There is no FDA guidance on use of Diphenhydramine (Injection) during labor and delivery.

### Nursing Mothers
There is no FDA guidance on the use of Diphenhydramine (Injection) in women who are nursing.

### Pediatric Use
- Diphenhydramine hydrochloride should not be used in neonates and premature infants.
- Diphenhydramine hydrochloride may diminish mental alertness, or, in the young pediatric patient, cause excitation. Overdosage may cause hallucinations, convulsions, or death.

### Geriatic Use
There is no FDA guidance on the use of Diphenhydramine (Injection) in geriatric settings.

### Gender
There is no FDA guidance on the use of Diphenhydramine (Injection) with respect to specific gender populations.

### Race
There is no FDA guidance on the use of Diphenhydramine (Injection) with respect to specific racial populations.

### Renal Impairment
There is no FDA guidance on the use of Diphenhydramine (Injection) in patients with renal impairment.

### Hepatic Impairment
There is no FDA guidance on the use of Diphenhydramine (Injection) in patients with hepatic impairment.

### Females of Reproductive Potential and Males
There is no FDA guidance on the use of Diphenhydramine (Injection) in women of reproductive potentials and males.

### Immunocompromised Patients
There is no FDA guidance one the use of Diphenhydramine (Injection) in patients who are immunocompromised.

# Administration and Monitoring

### Administration
- Intramuscular
- Intravenous

### Monitoring
There is limited information regarding Diphenhydramine (Injection) Monitoring in the drug label.

# IV Compatibility
There is limited information regarding the compatibility of Diphenhydramine (Injection) and IV administrations.

# Overdosage
- 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.

# Pharmacology

## Mechanism of Action
- 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.

## Structure
- 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 and has a molecular weight of 291.82. The molecular formula is C17H21NO - HCl. The structural formula is as follows:

## Pharmacodynamics
There is limited information regarding Diphenhydramine (Injection) Pharmacodynamics in the drug label.

## Pharmacokinetics
- 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.

## Nonclinical Toxicology
There is limited information regarding Diphenhydramine (Injection) Nonclinical Toxicology in the drug label.

# Clinical Studies
There is limited information regarding Diphenhydramine (Injection) Clinical Studies in the drug label.

# How Supplied
Diphenhydramine Hydrochloride Injection, USP is supplied as a sterile solution containing 50 mg diphenhydramine hydrochloride in each milliliter of solution with 0.1 mg/mL benzethonium chloride as a germicidal agent. Available in multi-dose 10 mL (NDC 67457-124-10) vials.
Manufactured for:
Mylan Institutional LLC 
Rockford, IL 61103 U.S.A.
Manufactured by:
Mylan Institutional 
Galway, Ireland
0499L104
MI:DIHYIJ:R2
REVISED JANUARY 2013

## Storage
- Store at 20 to 25C (68 to 77F).  Protect from freezing and light.

# Images

## Drug Images

## Package and Label Display Panel

### PRINCIPAL DISPLAY PANEL - 50 mg/mL
NDC 67457-124-10     10 mL
DiphenhydrAMINE 
Hydrochloride 
Injection, USP 
500 mg/10 mL 
(50 mg/mL)
For Intravenous or 
Intramuscular Use
HIGH POTENCY 
Rx only     Multi-Dose Vial
Usual Adult Dosage: 
0.2 mL to 1 mL 
intravenously or 
intramuscularly, or more 
as required. See
accompanying
prescribing information.
Store at 20 to 25C 
(68 to 77F). [See USP 
Controlled Room 
Temperature.]
Protect from freezing 
and light.
MI:124:1C:R3
Sterile. Pyrogen-Free.
Each mL contains: 
Diphenhydramine
Hydrochloride 50 mg,
Benzethonium Chloride
0.1 mg, as a germicidal
agent in Water for
Injection. The pH may
have been adjusted
with Sodium Hydroxide
and/or Hydrochloric
Acid.
Manufactured for:
Mylan Institutional LLC 
Rockford, IL 61103 U.S.A.
Manufactured by:
Mylan Institutional 
Galway, Ireland
Mylan.com

# Patient Counseling Information
- 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 activities requiring mental alertness such as driving a car or operating appliances, machinery, etc.

# Precautions with Alcohol
Alcohol-Diphenhydramine (Injection) interaction has not been established. Talk to your doctor about the effects of taking alcohol with this medication.

# Brand Names
- Benadryl
- Benylin Decongestant Cough
- Diphenhist
- Diphenyl
- Genahist
- Geridryl
- Nytol Quickcaps
- Nytol Quickgels

# Look-Alike Drug Names
- Benadryl - Benazepril
- DiphenhydrAMINE - DimenhyDRINATE

# Drug Shortage Status

# Price