Diphenhydramine Injection for Allergies, Motion Sickness, and Parkinsonism

Diphenhydramine Hydrochloride Injection is a sterile solution used as an antihistamine for treating allergic reactions when oral administration is not possible. It is also used for motion sickness and certain parkinsonism cases. This injectable form provides rapid action, safe for adults and children except premature infants and neonates.

Diphenhydramine Hydrochloride Injection is used in adults and pediatric patients (excluding premature infants and neonates) for:

• Relief of allergic reactions to blood or plasma and anaphylaxis as an adjunct after acute symptoms are controlled.
• Other immediate allergic conditions when oral therapy is not possible.
• Active treatment of motion sickness.
• Treatment of parkinsonism, particularly in the elderly unable to tolerate stronger medications, mild cases in other age groups, or as part of combination therapy with central anticholinergics when oral dosing is unsuitable.

Diphenhydramine Hydrochloride

Diphenhydramine is an antihistamine that blocks histamine from attaching to receptor sites on cells, reducing allergic symptoms. It also has anticholinergic (drying) and sedative effects. The injectable form acts quickly and distributes widely, including into the central nervous system.

Adults

Administer 10 to 50 mg intravenously at a rate not exceeding 25 mg/min, or deep intramuscularly. If needed, a dose of 100 mg may be given. The maximum daily dose is 400 mg.

Pediatric Patients (excluding premature infants and neonates)

The dose is 5 mg/kg per 24 hours or 150 mg/m² per 24 hours, divided into four doses administered IV or deep IM. The maximum daily dose is 300 mg. IV injections should not exceed 25 mg/min.

Important: Dosage should be individualized based on patient response. Inspect solutions for particulate matter and discoloration before use.

• Neonates and premature infants (due to safety concerns).
• Nursing mothers (antihistamines contraindicated due to risk to infants).
• Known hypersensitivity to diphenhydramine hydrochloride or antihistamines of similar chemical structure.
• Use as a local anesthetic (due to risk of local tissue necrosis).

• Not to be used in neonates or premature infants.
• Contraindicated in nursing mothers due to risks to infants.
• Should not be used as a local anesthetic due to risk of local tissue necrosis.
• Use cautiously in patients with narrow-angle glaucoma, peptic ulcer, pyloroduodenal obstruction, prostatic hypertrophy, or bladder-neck obstruction.
• Local necrosis has occurred with subcutaneous or intradermal injection of the IV product.
• In pediatric patients, overdose may cause hallucinations, convulsions, or death.
• May reduce mental alertness, cause sedation or excitation especially in young children.
• In elderly patients, increases risk of dizziness, sedation, and low blood pressure.

Common Adverse Reactions

• Urticaria, drug rash, photosensitivity reactions, excessive sweating, chills, dry mouth/nose/throat.
• Cardiovascular: Hypotension, headache, palpitations, rapid heartbeat, extrasystoles.
• Hematologic: Hemolytic anemia, thrombocytopenia, agranulocytosis.
• Nervous system: Sedation, drowsiness, dizziness, poor coordination, fatigue, confusion, restlessness, excitement, nervousness, tremor, irritability, insomnia, euphoria, numbness, blurred or double vision, vertigo, ringing in ears, neuritis, convulsions.
• Gastrointestinal: Stomach discomfort, nausea, vomiting, diarrhea, constipation.
• Genitourinary: Frequent urination, difficulty urinating, urinary retention, early menstrual flow.
• Respiratory: Thickened bronchial secretions, chest tightness, wheezing, nasal congestion.

• Alcohol and other central nervous system depressants (e.g., sedatives, tranquilizers, hypnotics) potentiate sedative and anticholinergic effects.
• Monoamine oxidase (MAO) inhibitors prolong and intensify anticholinergic effects.

Pregnancy

Classified as Pregnancy Category B. Animal studies have not shown harm to fetus or impaired fertility at doses up to 5 times the human dose, but adequate well-controlled studies in pregnant women are lacking. Use during pregnancy only if clearly needed.

Lactation

Contraindicated in nursing mothers due to higher risk of adverse effects on infants.

Overdose may cause central nervous system depression or stimulation, especially in children. Symptoms include dry mouth, dilated pupils, flushing, gastrointestinal distress, hallucinations, convulsions, or coma. Do not use stimulants. Vasopressors may be used for hypotension.

Store at controlled room temperature between 20° to 25°C (68° to 77°F), with permitted excursions from 15° to 30°C (59° to 86°F). Protect from light and keep the solution covered in its carton until use.