diphenhydrAMINE [Benadryl]

Question 1

Classification

Benadryl

Answer 1

Antihistamine

Question 2

Pharmacodynamics

Benadryl

Answer 2

Antihistamine with anticholinergic (drying) and sedative side effects. Antihistamines appear to compete with histamine for cell receptor sites on effector cells

Question 3

Pharmacokinetics

Benadryl

Answer 3

Intramuscular
 Onset - Rapid
 Peak - unknown
 Half-life - 1-4 hours
 Duration - 4-6 hours

Question 4

Indications

Benadryl

Answer 4

• Antihistaminic: adjunct treatment of allergic reactions / early anaphylaxis or as an adjunct to Epinephrine in anphylaxis
• Motion sickness
• Antiparkinsonism

Question 5

Contraindications

Benadryl

Answer 5

• Hypersensitivity to antihistamines
• Neonates
• Premature infants

Question 6

Precautions

Benadryl

Answer 6

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
• Hypertension
• Lower respiratory disease

Question 7

Adverse Effects (CNS)

Benadryl

Answer 7

Sedation, sleepiness, dizziness, disturbed coordination, fatigue, confusion, restlessness, excitation, nervousness, tremor, irritability, insomnia, euphoria, parethesia, blurred vision, diplopi, vertigo, tinnitus, acute labyrinthitis, neuritis, convulsions

Question 8

Adverse Effects

Benadryl

Answer 8

• Urticaria, drug rash, anaphylactic shock, photosensitivity, excessive perspiration, chills, dryness of mouth, nose and throat
• Hypotension, headache, palipations, tachycardia, extrasystoles
• Hemolytic Anemia, thrombocytopenia, agranulocytosis
• Epigasric distress, anorexia, nausea, vomiting, diarrhea, constipation
• Thickening of bronchial secretions, tightness of chest or throat and wheezing, nasal stuffiness

Question 9

Drug to Drug

Benadryl

Answer 9

• Additive effects with alcohol and other CNS depressants (hypnotics, sedative, tranquilizers, etc.)
• MAO inhibitors prolong and intesnsify the anticholinergic (drying) effect of antihistamines

Question 10

Warnings

Benadryl

Answer 10

Use with caution in patients with:

• Narrow-angle glaucoma
• Stenosing peptic ulcer
• Pyloroduodenal obstruction
• Symptomatic prostatic hypertrophy
• Bladder-neck obstruction

Question 11

Dosage

Benadryl

Answer 11

25 - 50mg IV for anaphylaxis

Question 12

Pediatric

Benadryl

Answer 12

1mg/Kg IM/IIV

see BCEHS Pediatric Dosage recommendations for age and weight-appropriate dosing informtation