DIPHENHYDRAMINE (BENADRYL)

CLASS:

• antihistamine

• H1 Blocker

ACTIONS: •

• Blocks histamine at H1 receptor sites (competes for these sites) with the following effects if successful: reversal of histamine induced bronchoconstriction, reversal of histamine induced vasodilation, reversal of histamine induced increased capillary permeability.

NOTE:

• H1 receptors causes bronchoconstriction and contraction of the gut

• Reverses drug induced extrapyramidal reactions (EPS) of muscle tremor and rigidity from phenothiazines (Trilafon, Stelazine, Compazine, Phenergan, Thorazine, Mellaril, Prolixin and others) and the butyrophenones (Haldol).

• mild sedative

INDICATIONS:

• allergic/anaphylactic reaction

• In anaphylaxis, Benadryl is given after Epinephrine because Epinephrine causes immediate bronchodilation by its Beta-2 effects and vasoconstriction by its alpha effects.

• Acute dystonic reactions (EPS)

CONTRAINDICATIONS:

• Hypersensitivity

• Lower respiratory diseases such as acute asthma attacks

• Use within 14 days of MAOIs

STANDARD PREP:

• 50 mg / ml

DOSAGE/ROUTE:

• See Hawaii S.O. 25-50 mg IV

PEDIATRIC DOSE:

• See Hawaii S.O. 1mg/kg IVP up to 25 mg

SIDE EFFECTS:

• sedation

• dry mouth

• thickening of bronchial secretions

• dizziness

PRECAUTION:

• Potentiates effects of ETOH/CNS depressants

• Children/neonates/premature infants are at risk of paradoxical reaction