Benadryl

Question 1

Action

Answer 1

• Binds to histamine receptor sites, blocking H1 and H2 receptors.
  
  • H1 causes bronchoconstriction, airway swelling, and vasodilation.
  • H2 causes secretion of gastric acid.
• Does not prevent histamine release

Question 2

Onset

Answer 2

15- 30 min

Question 3

Duration

Answer 3

6- 12 hours

Question 4

Indications

Answer 4

Allergic Reaction/ Anaphylaxis (S-122, S-162)
- mild & acute allergic reactions or anaphylaxis

Poisoning/ OD (S-134, S-165)
- extrapyramidal reactions

Question 5

Dosage/Route

Answer 5

ADULT:
50mg slow IV/IM

PEDS:
PDC IM/IV

Question 6

Contraindications

Answer 6

None

Question 7

Side Effects

Answer 7

• Drowsiness / sedation (excitement in children)
• Dry mouth / thickened bronchial secretions
• Hypotension
• Palpitations / tachycardia

Question 8

Special Information

Answer 8

Concentration: 50mg/ 1ml

1. For mild allergic reaction (rash, urticarial) Benadryl is the only medication.
2. For acute allergic reaction and anaphylaxis Epi IM is given first.
3. Cumulative depressant effects occur in the presence of alcohol and/or other sedatives.
4. Benadryl is priority in mild allergic reactions, epinephrine is priority in moderate/acute rxns.
5. Anticholinergic properties help to correct drug-induced cholinergic and dopaminergic imbalances that cause extrapyramidal reactions.
6. Extrapyramidal reaction may be seen 7-10 days after ingestion of medications.

Question 9

Class

Answer 9

Antihistamine

Question 10

Extrapyramidal reactions:

Answer 10

• Facial muscle twitch
• Full body spasm
• Neck muscle contraction
• Head deviation
• Occulogyrations