Drugs for Allergic Rhinitis

Drugs for Allergic Rhinitis

Overview

• Definition: Inflammation of nasal mucous membranes.

• Symptoms:

  • Sneezing

  • Itchy nose/eyes

  • Watery rhinorrhea (runny nose)

  • Nasal congestion

  • Nonproductive cough

• Triggers:

  • Allergen inhalation (e.g., dust, pollen, animal dander)

• Pathophysiology:

  • Caused by mast cell activation leading to the release of histamine, leukotrienes, and chemotactic factors.

  • Results in bronchiolar spasm, mucosal edema, and cellular infiltration.

• Treatment:

  • Antihistamines and intranasal corticosteroids are the preferred treatments.

Antihistamines

• Mechanism: H1 receptor antagonists manage symptoms of allergic rhinitis.

• Effectiveness: Especially effective for prevention in mild/intermittent disease.

• Types:

  • First-generation antihistamines:

    • Can cause sedation and anticholinergic effects.

    • Examples: Diphenhydramine, Chlorpheniramine.

  • Second-generation antihistamines:

    • Better tolerated with fewer side effects.

    • Examples: Fexofenadine, Loratadine, Cetirizine.

  • Topical antihistamines:

    • Fewer systemic effects.

    • Examples: Intranasal Olopatadine, Azelastine.

  • Combination products: Antihistamine-decongestant combos are effective for congestion.

Corticosteroids

• Most Effective Treatment: Intranasal corticosteroids are the most effective option for allergic rhinitis.

• Examples:

  • Beclomethasone

  • Budesonide

  • Fluticasone

• Benefits:

  • Improve sneezing, itching, rhinorrhea, nasal congestion.

• Onset: Effects seen within 3 to 36 hours; full effect in 1-2 weeks for chronic rhinitis.

• Side Effects: Minimal systemic absorption with localized adverse effects including nasal irritation, nosebleeds, sore throat, and rare candidiasis.

• Usage Advice: Avoid deep inhalation to effectively target nasal tissue.

Alpha-Adrenergic Agonists

• Short-acting agents:

  • Examples: Phenylephrine, Oxymetazoline.

• Mechanism: Constrict nasal arterioles, reduce airway resistance.

• Administration:

  • Intranasal: Rapid onset, minimal systemic effects, but use limited to ≤3 days to prevent rebound congestion.

  • Oral: Longer duration but can cause systemic effects (e.g., increased blood pressure, heart rate). Not recommended for long-term use.

Montelukast & Cromolyn

• Intranasal Cromolyn:

  • Effective when used before allergen exposure; start 1–2 weeks prior.

• Leukotriene Receptor Antagonists:

  • Monotherapy or combination therapy for allergic rhinitis; suitable for patients with coexisting asthma.

• Intranasal Ipratropium:

  • Treats rhinorrhea but not effective for sneezing or congestion.

Drugs for Cough

Overview

• Cough: A defense mechanism in response to irritants.

• Causes:

  • Common cold, sinusitis, chronic respiratory diseases.

• Important Note: Identification of the underlying cause is crucial before treatment.

• Treatment Goals: Manage underlying causes; may include antibiotics if bacterial etiology is suspected.

Antitussives

• Suppress cough; differ from expectorants which clear mucus in productive cough.

Opioids

• Codeine:

  • Reduces cough sensitivity in the CNS at low doses.

  • Adverse effects: Constipation, dysphoria, fatigue, addictive potential limits usage.

  • CYP2D6: Metabolizes codeine to morphine, risk for ultra-rapid metabolizers.

• Dextromethorphan:

  • Blocks medullary cough reflex and NMDA receptors.

  • No analgesic effects at antitussive doses.

  • Fewer side effects than codeine but low addiction risk at low doses; potential for abuse at high doses (dysphoria).

  • Risk of serotonin syndrome with serotonergic medications.

Benzonatate

• Mechanism: Provides peripheral cough suppression by anesthetizing stretch receptors in respiratory passages, lungs, and pleura.

• Precautions: May cause dizziness and numbness; swallow whole with water, avoiding chewing to prevent mucosal irritation.

Guaifenesin

• Mechanism: An expectorant that reduces mucus viscosity, enhancing mucociliary clearance.

• Uses: Converts dry cough to productive cough; available as a single ingredient or combined with codeine/dextromethorphan.

• Adverse Effects: Can cause GI disturbances, dizziness, headache, and rash; excessive use can lead to kidney stone formation.

Acetylcysteine

• Mechanism: Reduces sputum viscosity by breaking disulfide bonds in mucoproteins.

• Uses:

  • Used orally in COPD.

  • Used as IV antidote for acetaminophen poisoning.

• Adverse Effects:

  • Oral: Nausea, vomiting, stomatitis.

  • IV: Rash, drug fever, itching, rare anaphylaxis.

• Usage Tip: Mix with cola or fruit juice to mask unpleasant odor.