Respiratory Drugs and Histamine

• Respiratory drugs affect the upper respiratory system and the lower respiratory system.

Classes of Respiratory Drugs

• Antitussives (non-opioid) such as dextromethorphan and benzonatate, are cough suppressants.
• Decongestants such as pseudoephedrine clear congestion in nasal membranes.
• Antihistamines such as diphenhydramine antagonize or block histamine.
  • Histamine triggers allergies and is released by leukocytes.
• Expectorants such as guaifenesin loosen mucus in the lower respiratory tract.
  • This promotes a more productive cough.

Histamine

• Histamine is a chemical messenger released by mast cells, basophils, and neutrophils.
• Histamine causes inflammatory responses triggered by allergens or irritation.
• Histamine causes vasodilation, increases vascular permeability, and leads to symptoms like itching (pruritus), hives (urticaria), sneezing, runny nose (rhinorrhea), hypotension, and diarrhea.

Disorders of the Lower Respiratory System

• Chronic bronchitis
• Bronchiectasis
• Cystic fibrosis

Classes of Drugs Used To Treat Disorders of the Lower Respiratory System

• Bronchodilators
• Anti-inflammatory agents
• Mucolytics

Leukotrienes

• Leukotrienes cause airway irritation and increased mucous production.
• Leukotrienes lower gas exchange.
• The arachidonic acid enters the lipooxygenase pathway, which turns into leukotrienes.
• Leukotrienes cause bronchoconstriction, increase airway inflammation, increase mucous production and decrease gas exchange

Dextromethorphan

• Class: Non-Opioid Antitussive
• MOA: Suppresses cough reflex by working directly on the cough center in the medulla.
• Indications: Chronic, non-productive cough.
• Contraindications: Advanced CV disease, HTN, hyperthyroidism, glaucoma (increases intraocular pressure), pregnancy.
• Adverse Effects: Nausea, drowsiness, restlessness, irritability.
• Nursing Considerations: Use cautiously (if at all) in COPD or asthma patients; avoid suppressing cough reflex; do not mix with alcohol.

Benzonatate (Tessalon Perles)

• Class: Non-Opioid Antitussive
• MOA: Suppresses cough by topical anesthesia on respiratory stretch receptors, numbing the throat.
• Indications: Acute cough from common cold or influenza.
• Contraindications: Pregnancy; check with OB.
• Adverse Effects: Drowsiness, dizziness, headache, nausea.
• Nursing Considerations: Pregnancy category C.

Pseudoephedrine (Pseudophed)

• Class: Decongestant
• MOA: Shrinks swollen membranes in the bronchi.
• Indications: Common cold, sinusitis, allergic rhinitis.
• Contraindications: Severe HTN, coronary artery disease (CAD), narrow angle glaucoma.
• Adverse Effects: Sympathomimetic effects on CNS & CVS, stimulates similar to CNS.
• Nursing Considerations: High abuse potential (used to make methamphetamine); patient education includes not overusing nasal spray,Reading OTC labels and warning patients of potential adverse effects; avoid smoke-filled rooms & use humidifier.

Diphenhydramine (Benadryl)

• Class: Antihistamine (1st generation, SEDATING)
• MOA: H1 antagonist; causes drowsiness because it crosses the blood-brain barrier.
• Indications: Allergic reactions.
• Contraindications: Use with extreme caution when combined with CNS depressants.
• Adverse Effects: Anorexia, anti-SLUDGE (Salivation, Lacrimation, Urination, Defecation, GI upset, Emesis), drowsiness.
• Nursing Considerations: Possible paradoxical effect in children and the elderly.

Loratadine (Claritin)

• Class: Antihistamine, 2nd Generation, NON-SEDATING
• MOA: H1 blocker that does not cross the blood-brain barrier well, making it not as drowsy.
• Indications: Seasonal allergies, best if taken before symptoms onset.
• Contraindications: Use with extreme caution when combined with CNS depressants.
• Adverse Effects: Headache, anxiety, fatigue.
• Nursing Considerations: Can have a paradoxical effect in children and the elderly.

Guaifenesin (Mucinex)

• Class: Expectorant
• MOA: Liquefies lower respiratory tract secretions.
• Indications: Thin secretions, non-productive cough.
• Adverse Effects: Heart palpitations, cardiac disease.
• Nursing Considerations: Liquid guaifenesin contains alcohol & contact provider if cough is >7 days.

Acetylcysteine (Mucomyst)

• Class: Mucolytic
• MOA: Acts directly on mucous to thin secretions in nebulized form.
• Indications: Respiratory issues, COPD, cystic fibrosis.
• Adverse Effects: Trigger bronchospasms.
• Nursing Considerations: Bad taste & to ensure it is effective, assess lung sounds before and after.

Albuterol

• Class: Bronchodilator (Beta-2 agonist)
• MOA: Dilates Bronchioles
• Indications: Asthma and COPD.
• Adverse Effects: Nausea, increased HR, palpitations, and angina.
• Nursing Considerations: This is a rescue drug.
  • Has better results when given with Acetylcysteine
  • Call 911 if symptoms do not go away.
  • In IV form it binds with acetaminophen and protects liver cells improving their renal function.
  • Use a spacer to allow medication to travel deeper into the lungs.

Salmeterol

• Class: Long-acting beta-2 agonist bronchodilator.
• MOA: Long-acting beta-2 agonist.
• Indications: Asthma, COPD (off-label use).
• Nursing Considerations: Maintenance medication; not a rescue drug.
  • Given before other inhalers such as Duoneb or Flovent

Ipratropium Bromide (Atrovent)

• Class: Anticholinergic bronchodilator.
• MOA: Cholinergic antagonist that opens bronchi.
• Indications: Asthma, COPD.
• Contraindications: Sensitivity to atropine.
• Adverse Effects: Hoarseness.
• Nursing Considerations: Not a rescue drug.

Theophylline (Theo-Dur)

• Class: Xanthine
• MOA: Relaxes bronchial smooth muscles and increases respiratory drive.
• Indications: Asthma.
• Adverse Effects: GERD, GI, anorexia, palpitations, tachycardia, dysrhythmia.
• Nursing Considerations: There is no antidote, but try charcoal. Therapeutic window: 10-20 mcg/mL

Fluticasone (Flovent)

• Class: Inhaled Glucocorticoid
• MOA: Reduces airway inflammation, increases sensitivity of beta-2 receptors.
• Indications: Allergies, COPD
• Contraindications: Active systemic fungal infection and cataracts.
• Adverse Effects: Throat irritation and dry cough.
• Nursing Considerations: educate the patient on rinsing out their mouth after use to prevent thrush. This is not for status asthmaticus (severe asthma attack)

Montelukast (Singulair)

• Class: Leukotriene Receptor Antagonist
• MOA: Blocks leukotriene receptors.
• Indications: Asthma and COPD.
• Adverse Effects: Muscle aching, burning, paresthesia.
• Nursing Considerations: Maintenance medication and must take even if the indications are not currently felt.