Non-Sedating Antihistamines

• Second-generation antihistamines offer fewer side effects than sedating antihistamines.
• As peripherally acting antihistamines, they are available over-the-counter (OTC), leading to increased use.
• Nonsedating antihistamines are used therapeutically for allergic rhinitis and chronic idiopathic urticaria.

Prototype and Other Medications

• Cetirizine is the prototype nonsedating antihistamine.
• Other nonsedating antihistamines include loratadine, fexofenadine, and desloratadine.

Expected Pharmacologic Action

• Nonsedating antihistamines antagonize histamine effects at H1 receptor sites, without binding to or inactivating histamine.
• They have minimal anticholinergic effects compared to sedating antihistamines.
• Cetirizine is effective for seasonal allergic rhinitis and idiopathic urticaria.
• Therapeutic effects are longer lasting, allowing for once-daily dosing.

Adverse Drug Reactions

• Nonsedating antihistamines produce significantly fewer side effects than sedating antihistamines; side effects may be dose-related.
• Drowsiness and fatigue may still occur, but less so than with first-generation antihistamines.
• Mild anticholinergic effects, such as dry mouth, nose, and throat, may also occur, but less frequently.

Interventions

• Assess clients for drowsiness and fatigue during ambulation, especially with dosages exceeding 10 mg per day.
• Provide water for dry mouth or throat.
• Suggest sucking on hard candy to relieve dryness.
• Encourage fluid intake of 1,500 to 2,000 mL per day to reduce secretion viscosity.

Administration

• Nonsedating antihistamines can be taken with or without food.
• Do not administer with other over-the-counter antihistamines.
• Reduce the dose of nonsedating antihistamines in clients with compromised liver or kidney function.

Client Instructions

• Take nonsedating antihistamines once daily at a convenient time.
• Avoid driving or activities requiring mental alertness until the amount of drowsiness is known.
• Take frequent sips of water and suck on hard candy for dry mouth and throat.

Contraindications and Precautions

• Do not give to infants under 6 months of age or breastfeeding women.
• Avoid use in individuals with allergies to H1-antihistamine receptors or hydroxyzine.
• Use cautiously in clients with impaired kidney or liver function due to the risk of delayed metabolism and excretion.

Interactions

• Theophylline can reduce the clearance of nonsedating antihistamines, potentially leading to toxicity.
• Concurrent use with sedative/hypnotics, opioid analgesics, or alcohol can potentiate CNS depression.

Question Answer

• The correct answer is d: Administer the medication prophylactically during allergy seasons.

Second-generation antihistamines have fewer side effects than sedating ones. They are peripherally acting and available over-the-counter, increasing their use. These medications are used for allergic rhinitis and chronic idiopathic urticaria.