Diphenhydramine Injection

Product Overview

Diphenhydramine Injection is a prescription injectable formulation of diphenhydramine hydrochloride, a first-generation antihistamine. It is commonly used to treat allergic reactions, anaphylaxis, motion sickness, and symptoms of urticaria or pruritus.

Diphenhydramine works by blocking histamine H1 receptors, reducing the effects of histamine in the body, such as itching, swelling, and vasodilation. Injectable administration allows rapid onset of action, making it ideal for acute allergic reactions or situations where oral administration is not feasible.

This medication is available by prescription only and must be administered under licensed healthcare supervision.

Dosage & Administration

General Dosing Information

Dosing of Diphenhydramine Injection is individualized based on the patient’s age, weight, clinical condition, and therapeutic goals.

Typical Adult Use (Examples)

• Administered intramuscularly (IM), intravenously (IV), or slow IV push
• Dose depends on severity of allergic reaction or targeted use
• Commonly used for:
  • Acute allergic reactions and anaphylaxis
  • Urticaria or itching
  • Adjunctive therapy for motion sickness or sedation protocols

Administration Details

• Supplied as a sterile injectable solution
• Inspect solution prior to use; do not use if cloudy, discolored, or containing particulate matter
• Use aseptic technique during preparation and administration
• Administer slow IV injection to reduce risk of hypotension or sedation
• Rotate IM injection sites to minimize irritation
• Dispose of needles and syringes in approved sharps containers

Patients should not self-administer unless properly trained and authorized by their healthcare provider.

Treatment Duration & Monitoring

Treatment duration depends on the patient’s condition:

• Single or short-term administration for acute allergic reactions
• Monitoring may include:
  • Clinical assessment of symptom relief
  • Observation for sedation, hypotension, or injection-site reactions
  • Vital signs monitoring during IV administration, especially in high-risk patients

Therapy should be adjusted based on patient response and provider evaluation.

Mechanism of Action

Diphenhydramine Injection works by:

• Blocking H1 histamine receptors, reducing histamine-mediated effects such as vasodilation, increased vascular permeability, and pruritus
• Producing anticholinergic effects that contribute to sedation and relief of motion sickness
• Rapid onset when administered parenterally allows effective management of acute allergic reactions

Contraindications & Precautions

Diphenhydramine Injection should be used with caution or avoided in patients with:

• Known hypersensitivity to diphenhydramine or other antihistamines
• Severe asthma, glaucoma, or urinary retention without monitoring
• Cardiac arrhythmias or hypotension
• Infants or elderly patients may be more sensitive to sedative and anticholinergic effects

This product is intended for medically supervised use only.

Drug Interactions

Patients should inform their healthcare provider of all medications and supplements. Diphenhydramine may interact with:

• CNS depressants, alcohol, or sedatives (additive sedation)
• Anticholinergic medications (enhanced effects)
• Certain MAO inhibitors (may potentiate anticholinergic effects)

Clinical judgment should guide concurrent therapy.

Adverse Reactions & Side Effects

Common

• Sedation or drowsiness
• Mild injection-site discomfort
• Redness or swelling at injection site

Less Common

• Dizziness or hypotension
• Nausea or gastrointestinal upset
• Dry mouth, blurred vision, urinary retention (anticholinergic effects)
• Rare hypersensitivity reactions

Seek medical attention for persistent, severe, or allergic reactions.

Pregnancy & Breastfeeding

Use during pregnancy or breastfeeding should occur only when medically indicated and under the supervision of a licensed healthcare provider. Patients should consult their provider before use.

Storage & Handling

• Store according to Angel Pharmacy compounding and dispensing guidelines
• Typically stored at controlled room temperature
• Protect from light
• Do not freeze
• Keep out of reach of children and pets

Unused or expired medication should be disposed of according to pharmacy or healthcare facility protocols.

Important Notice

This information is provided for educational purposes only and does not replace professional medical advice. All dosing, administration, and treatment decisions must follow the instructions of the prescribing healthcare provider.