7. ANTIHISTAMINES
DRUG NAME chlorpheniramine, diphenhydramine, promethazine loratadine, fexofenadine, cetirizine, and levocetirizine
CLASS First generation antihistamines Second generation antihistamines
MOA Block H1 receptors, resulting in bronchodilation, vasoconstriction, and decreased vascular permeability
INDICATIONS
•Allergic rhinitis, conjunctivitis
•Urticaria, Anaphylaxis
•Common cold, Nausea and vomiting, Motion sickness
•Insomnia
ROA PO, TOP, IV, IM
SIDE EFFECTS
•Anticholinergic side effects; dry mouth, blurred vision, urinary retention, constipation
•Sedation, Orthostatic hypotension, Drowsiness, Irritability, Confusion
•QT prolongation, Arrhythmia
•Tinnitus, Wheezing
CONTRA
INDICATIONS
AND CAUTIONS
•Pregnancy, breastfeeding, newborns
•Narrow-angle glaucoma, Benign prostatic hyperplasia
•Arrhythmia
•Taking other medications that prolong QT interval (e.g.,
erythromycin, amitriptyline)
•Taking other substances that alter mental status (e.g.,
alcohol, barbiturates, opioids and hypnotics)
•Boxed warning (promethazine): < 2 years of age
(respiratory depression); severe tissue injury if
administered IV
•Renal or hepatic disease
8. ANTIHISTAMINES
ASSESSMENT
AND
MONITORING
Assess symptoms - Type; e.g., sneezing, nasal congestion, runny nose and itchy or watery eyes
• Frequency; occasional, seasonal, year around, environmental
•Laboratory results - Liver and renal function tests
•Medical history
• QT interval prolongation; medications affecting QT interval
• Narrow-angle glaucoma
• Prostatic enlargement
• Advanced age, Pregnancy, breastfeeding
•Physical assessment - Vital signs, Lung sounds
•Side effects
CLIENT
EDUCATION
Identify and reduce exposure to allergens
Self-administration
• Take as directed; with or without food
• Fexofenadine oral disintegrating tablets: take on an empty stomach without water or juice; place the
tablet directly on tongue; avoid juices like apple or orange juice for at least 4 hours before and after
administration
Management of side effects
• Sedation: caution with activities requiring alertness or concentration; avoid alcohol and other
sedating medications
• Anticholinergic effects
• Dry mouth: sips of water, sugarless gum or hard candy
• Constipation: increase fluid, fiber and physical activity
• Orthostatic hypotension: make position changes slowly