Diphenhydramine: class, trade name, action
- Class: Antihistamine
- Trade Name: Benadryl
- Action: Is an antihisamine w/significant anticholinergic activity. Treats allergic reaction and anaphylaxis. It competes for H1 receptor sites on effector cells, thus blocking histamine release. Its effects in parkinsonism and drug induced extrapyramidal symptoms are apparently related to its ability to suppress central cholinergic activityand to prolong action of dopamine by inhibiting its reuptake and storage. It does not inhibit gastric secretion but has strong antiemetic effect.
Diphenhydramine: Uses, Dosages, Pharmacokinetics and Interactions
- Use: to decrease the effects of allergic reactions and the extrapyramidal symptoms following an antipsychotic medication
- Dosage: Adult- 25 to 50 mg IV/IM Peds- 2 to 5 mg/kg IV/IM
- Onset is 15 to 30 min Duration is under 10 min
- Does not cross blood-brain barrier
- Inactive in the liver, kidney and plasma by monoamine oxidase and COMT
- Excreted in Urine
- Interactions: Alcohol and other CNS depressants, MAO inhibitors compound CNS depression.
DIPHENHYDRAMINE: Contraindications and Precautions
- Hypersensitivity to antihistamines of similar structure, lower respiratory tract symptoms (including acute asthma), narrow angle glaucoma, prostatic hypertrophy, bladder neck obstruction, GI obstruction or stenosis, pregnancy, nursing mothers, premature infants, newborns and use as nighttime sleep aid in children under 12.
- Precautions: in pts with a history of asthma, convulsive disorders, increased intraocular pressure, hyperthyroidism, hypertension, cardiovascular disease, diabetes, elderly pts, infants and young chidren
DIPHENHYDRAMINE: side effects, considerations
- CNS: drowsiness, dizziness, headache, fatigue, disturbed coordination, tingling, heaviness and weakness of hands, tremors, euphoria, nervousness, restlessness, insomnia, confusion, excitement, fever
- CV: Palpitation, tachycardia, mild hypo or hypertension, cardiovascular collapse
- ENT: Tinnitus, vertigo, dry nose and throat, blurred vision, diplopia (double vision), photosensitivity, dry eyes
- GI: dry mouth, nausea, epigastric distress, anorexia, vomiting, constipation or diarrhea
- Skin: rash, urticaria, photosensitivity, anaphylactic shock
- Respiratory: thickened bronchial secretions, wheezing, chest tightness
- Considerations: Administer IM deep into large muscle, May be given direct IV undiluted rate of 25mg over 1 minute, pts w/BP problems who r receiving the drug parenterally should be closely monitored.