The document outlines various antihistamines, classifying them into first and second generation, along with their mechanisms of action, indications, routes of administration, and potential side effects. It discusses contraindications and cautions in usage, highlights the importance of assessment and monitoring, and provides client education on self-administration and management of side effects. Additionally, it lists specific drug names and dosages for both sedative and non-sedative antihistamines.

1. Antihistamines

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

9. Drug Dose Preparations
HIGHLY SEDATIVE
Diphenhydramine
Dimenhydrinate
Promethazine
Hydroxyzine
25–50 mg
BENADRYL 25, 50 mg cap., 12.5 mg/5ml syr.
DRAMAMINE 16 mg/5 ml syr, 50 mg tab
PHENERGAN 10, 25 mg tab., 5 mg/ml elixer, 25 mg/ml inj
ATARAX 10, 25 mg tab., 10 mg/5 ml syr, 6 mg/ml drops, 25
mg/ml inj.
MODERATELY SEDATIVE
Pheniramine
Meclozine (Meclizine)
Cinnarizine
20–50 mg oral, IM
AVIL 25 mg, 50 mg tab, 15 mg/5 ml syr, 22.5 mg/ml inj.
In DILIGAN 12.5 mg + niacin 50 mg tab
In PREGNIDOXIN 25 mg + Caffeine 20 mg tab
STUGERON, VERTIGON 25 and 75 mg tab.
MILD SEDATIVE
Chlorpheniramine
Dexchlorpheniramine
2–4 mg (0.1
mg/kg)
2 mg oral
PIRITON, CADISTIN 4 mg tab
POLARAMINE 2 mg tab, 0.5 mg/ 5 ml syr
SECOND GENERATION
ANTIHISTAMINICS
Fexofenadine
Loratadine
Desloratadine
Cetirizine
Levocetirizine
120–180 mg oral
10 mg oral
5 mg oral
10 mg oral
5–10 mg oral
ALLEGRA, ALTIVA, FEXO 120, 180 mg tab
LORFAST, LORIDIN, LORMEG, 10 mg tab, 1mg/ml susp.
DESLOR, LORDAY, NEOLORIDIN 5 mg tab
ALERID, CETZINE, ZIRTIN, SIZON 10 mg tab,
LEVOSIZ, LEVORID, TECZINE 5, 10 mg tab, 5mg/5ml syr
LEVOCET 5 mg tab, 2.5mg/5 ml syr