UNIT-4- Drugs acting on respiratory system

Introduction to Drugs Acting on the Respiratory System

Introduction

The respiratory system is responsible for oxygen exchange and removal of carbon dioxide. Various conditions such as asthma, chronic obstructive pulmonary disease (COPD), respiratory infections, and allergic reactions require pharmacological intervention.

Drugs acting on the respiratory system help in bronchodilation, reducing inflammation, thinning mucus, and suppressing cough to improve breathing and manage respiratory diseases. These drugs work by targeting airway smooth muscles, inflammatory mediators, and mucous secretion.

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1. Classification of Drugs Acting on the Respiratory System

A. Bronchodilators (Relieve Airway Obstruction)

1. Beta-2 Adrenergic Agonists – Stimulate β2 receptors, causing airway relaxation.
   • Examples: Salbutamol, Terbutaline, Salmeterol, Formoterol
2. Anticholinergics (Muscarinic Antagonists) – Block muscarinic receptors, preventing bronchoconstriction.
   • Examples: Ipratropium, Tiotropium
3. Methylxanthines – Increase cAMP levels, relaxing bronchial smooth muscles.
   • Examples: Theophylline, Aminophylline

B. Anti-Inflammatory Agents (Reduce Airway Inflammation)

1. Corticosteroids – Suppress inflammation and immune response.
   • Examples: Budesonide, Fluticasone, Prednisolone
2. Leukotriene Receptor Antagonists (LTRAs) – Block leukotrienes that cause inflammation.
   • Examples: Montelukast, Zafirlukast
3. Mast Cell Stabilizers – Prevent histamine release from mast cells.
   • Examples: Cromolyn Sodium, Nedocromil
4. Biologic Therapy (Monoclonal Antibodies) – Target specific immune pathways in asthma.
   • Examples: Omalizumab (anti-IgE), Mepolizumab (anti-IL-5)

C. Mucolytics and Expectorants (Clear Mucus from Airways)

1. Mucolytics – Break down thick mucus.
   • Examples: Acetylcysteine, Carbocisteine
2. Expectorants – Increase secretion clearance.
   • Examples: Guaifenesin, Ammonium Chloride

D. Antitussives (Suppress Cough)

1. Opioid Cough Suppressants – Suppress cough reflex via central action.
   • Examples: Codeine, Dextromethorphan
2. Non-Opioid Antitussives – Reduce irritation without opioid effects.
   • Examples: Benzonatate, Pholcodine

E. Respiratory Stimulants (Stimulate Breathing in Apnea)

• Examples: Doxapram, Caffeine Citrate (for neonatal apnea)

F. Antihistamines (Control Allergic Reactions)

• Examples: Loratadine, Cetirizine, Diphenhydramine

G. Decongestants (Reduce Nasal Congestion)

• Examples: Phenylephrine, Pseudoephedrine, Oxymetazoline

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2. Importance of Respiratory Drugs in Clinical Practice

• Bronchodilators are the mainstay of treatment for asthma and COPD.
• Corticosteroids and leukotriene inhibitors help prevent inflammation and recurrent attacks.
• Mucolytics and expectorants aid in clearing airway secretions in chronic respiratory conditions.
• Antitussives and decongestants provide symptomatic relief in upper respiratory infections.
• Biologic therapy is used in severe allergic asthma where conventional treatments fail.

Nurses play a critical role in administering respiratory drugs, monitoring therapeutic effects, educating patients, and managing adverse reactions to ensure effective respiratory disease management.

Pharmacology of Commonly Used Anti-Asthmatic Drugs

Introduction

Asthma is a chronic inflammatory disease of the airways characterized by bronchoconstriction, airway inflammation, and excessive mucus production. The main goals of asthma treatment are bronchodilation, inflammation control, and prevention of exacerbations.

Anti-asthmatic drugs act by relaxing airway smooth muscles, reducing inflammation, and preventing bronchial hypersensitivity.

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1. Classification of Anti-Asthmatic Drugs

A. Bronchodilators (Relieve Bronchospasm)

1. Beta-2 Adrenergic Agonists
   • Examples: Salbutamol, Terbutaline, Salmeterol, Formoterol
   • Action: Stimulate β2 receptors, relaxing airway smooth muscles.
2. Anticholinergics (Muscarinic Antagonists)
   • Examples: Ipratropium, Tiotropium
   • Action: Block muscarinic (M3) receptors, preventing bronchoconstriction.
3. Methylxanthines
   • Examples: Theophylline, Aminophylline
   • Action: Increase cAMP, leading to bronchodilation.

B. Anti-Inflammatory Agents (Control Inflammation)

1. Inhaled Corticosteroids (ICS)
   • Examples: Budesonide, Fluticasone, Beclomethasone
   • Action: Suppress inflammation, decrease eosinophil activity.
2. Leukotriene Receptor Antagonists (LTRAs)
   • Examples: Montelukast, Zafirlukast
   • Action: Block leukotrienes, preventing airway inflammation.
3. Mast Cell Stabilizers
   • Examples: Cromolyn Sodium, Nedocromil
   • Action: Prevent mast cell degranulation, reducing histamine release.
4. Monoclonal Antibodies (Biologics)
   • Examples: Omalizumab (anti-IgE), Mepolizumab (anti-IL-5)
   • Action: Target specific immune mediators, preventing inflammation.

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2. Pharmacology of Common Anti-Asthmatic Drugs

1. Salbutamol (Short-Acting Beta-2 Agonist – SABA)

Composition

• Salbutamol (Albuterol) sulfate

Action

• Stimulates β2 receptors → Bronchodilation and reduced airway resistance.

Dosage and Route

• Inhalation (MDI/Nebulizer): 100–200 mcg every 4–6 hours as needed.
• Oral (Tablet/Syrup): 2–4 mg three times daily.
• IV (Severe Cases): 250–500 mcg IV every 6–8 hours.

Indications

• Acute asthma attack
• Exercise-induced bronchospasm
• Chronic obstructive pulmonary disease (COPD)

Contraindications

• Severe cardiac disease (risk of tachycardia).
• Uncontrolled hypertension.

Drug Interactions

• Beta-blockers (e.g., Propranolol) reduce its effect.
• Diuretics, steroids increase hypokalemia risk.

Side Effects

• Tremors, palpitations, headache.

Adverse Effects

• Tachycardia, arrhythmias, paradoxical bronchospasm.

Toxicity

• Overdose Symptoms: Severe tachycardia, muscle cramps, seizures.
• Management: Beta-blockers (e.g., Propranolol), IV fluids, ECG monitoring.

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2. Ipratropium Bromide (Short-Acting Muscarinic Antagonist – SAMA)

Composition

• Ipratropium bromide

Action

• Blocks M3 receptors, preventing bronchoconstriction.

Dosage and Route

• Inhalation (MDI/Nebulizer): 20–40 mcg every 6–8 hours.

Indications

• Acute asthma attack (adjunct therapy)
• COPD (first-line therapy)

Contraindications

• Glaucoma, prostatic hyperplasia (risk of urinary retention).

Drug Interactions

• Increases effects of beta-agonists (synergistic bronchodilation).

Side Effects

• Dry mouth, blurred vision.

Adverse Effects

• Paradoxical bronchospasm, urinary retention.

Toxicity

• Overdose Symptoms: Tachycardia, delirium.
• Management: Supportive care, IV fluids.

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3. Theophylline (Methylxanthine)

Composition

• Theophylline, Aminophylline (IV form)

Action

• Inhibits phosphodiesterase (PDE) → Increases cAMP → Bronchodilation.
• Stimulates the central nervous system (CNS) → Improves respiratory drive.

Dosage and Route

• Oral: 200–400 mg once or twice daily.
• IV (Emergency): 5 mg/kg loading dose, then 0.5 mg/kg/hour.

Indications

• Chronic asthma, COPD
• Apnea in preterm infants

Contraindications

• Epilepsy (lowers seizure threshold).
• Severe heart disease (risk of arrhythmias).

Drug Interactions

• Caffeine increases toxicity risk.
• Fluoroquinolones, macrolides increase theophylline levels (risk of toxicity).

Side Effects

• Nausea, insomnia, tremors.

Adverse Effects

• Severe arrhythmias, seizures, hypotension.

Toxicity

• Overdose Symptoms: Seizures, severe vomiting.
• Management: Activated charcoal, IV beta-blockers (for arrhythmias).

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4. Montelukast (Leukotriene Receptor Antagonist – LTRA)

Composition

• Montelukast sodium

Action

• Blocks leukotriene receptors → Reduces airway inflammation and bronchoconstriction.

Dosage and Route

• Oral: 10 mg once daily at bedtime.

Indications

• Asthma prophylaxis
• Exercise-induced bronchospasm
• Allergic rhinitis

Contraindications

• Acute asthma attacks (not for rescue use).

Drug Interactions

• Phenytoin, rifampin reduce montelukast levels.

Side Effects

• Headache, abdominal pain.

Adverse Effects

• Neuropsychiatric symptoms (aggression, depression, suicidal thoughts).

Toxicity

• Overdose Symptoms: Hyperactivity, dizziness.
• Management: Supportive care, IV fluids.

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5. Budesonide (Inhaled Corticosteroid – ICS)

Composition

• Budesonide, Fluticasone, Beclomethasone

Action

• Inhibits inflammatory mediators → Decreases eosinophil activity and prevents asthma exacerbations.

Dosage and Route

• Inhalation (MDI/DPI): 100–400 mcg twice daily.

Indications

• Chronic asthma maintenance therapy
• COPD with frequent exacerbations

Contraindications

• Acute asthma attacks (not for immediate relief).

Drug Interactions

• NSAIDs increase risk of gastric ulcers.

Side Effects

• Oral thrush, hoarseness.

Adverse Effects

• Osteoporosis, growth suppression in children (long-term use).

Toxicity

• Overdose Symptoms: Cushing’s syndrome, adrenal suppression.
• Management: Tapering dose, calcium supplements.

Pharmacology of Bronchodilators and Salbutamol Inhalers

Introduction

Bronchodilators are drugs that relax airway smooth muscles, leading to bronchodilation and improved airflow. These drugs are primarily used to treat asthma, chronic obstructive pulmonary disease (COPD), and other respiratory conditions with bronchospasm.

Salbutamol (Albuterol) inhalers are among the most commonly used short-acting beta-2 agonists (SABAs) for the acute relief of asthma and COPD symptoms.

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1. Classification of Bronchodilators

A. Beta-2 Adrenergic Agonists (Stimulate β2 Receptors)

1. Short-Acting Beta Agonists (SABAs) – Used for quick relief.
   • Examples: Salbutamol (Albuterol), Terbutaline
2. Long-Acting Beta Agonists (LABAs) – Used for maintenance therapy.
   • Examples: Salmeterol, Formoterol

B. Anticholinergics (Muscarinic Antagonists)

1. Short-Acting Muscarinic Antagonists (SAMAs) – Used for acute relief.
   • Example: Ipratropium Bromide
2. Long-Acting Muscarinic Antagonists (LAMAs) – Used for chronic therapy.
   • Example: Tiotropium, Aclidinium

C. Methylxanthines (Increase cAMP for Bronchodilation)

• Examples: Theophylline, Aminophylline

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2. Pharmacology of Salbutamol Inhalers (Short-Acting Beta-2 Agonist – SABA)

1. Salbutamol Inhaler

Composition

• Salbutamol (Albuterol) Sulfate 100 mcg per puff
• Metered-dose inhaler (MDI) or dry powder inhaler (DPI)

Action

• Stimulates β2-adrenergic receptors in the lungs → Relaxation of bronchial smooth muscle → Bronchodilation
• Inhibits mast cell degranulation, reducing histamine release.
• Increases mucociliary clearance, improving airway function.

Dosage and Route

• Inhalation (MDI/DPI):
  • Acute asthma attack: 1–2 puffs (100–200 mcg) every 4–6 hours
  • Exercise-induced bronchospasm: 2 puffs, 15 minutes before exercise
  • Nebulizer (Severe Asthma): 2.5 mg every 6–8 hours
• Oral (Tablets/Syrup):
  • 2–4 mg three times daily (for maintenance therapy)

Indications

• Acute asthma exacerbations (Rescue inhaler)
• Exercise-induced bronchospasm (Preventive use)
• COPD with reversible airway obstruction

Contraindications

• Severe cardiac disease (risk of tachycardia, arrhythmias).
• Uncontrolled hypertension.
• Hyperthyroidism (may increase heart rate excessively).

Drug Interactions

• Beta-blockers (e.g., Propranolol) reduce the bronchodilator effect.
• Diuretics and corticosteroids increase risk of hypokalemia.
• Monoamine oxidase inhibitors (MAOIs) and tricyclic antidepressants increase cardiovascular side effects.

Side Effects

• Tremors
• Palpitations
• Headache
• Nervousness

Adverse Effects

• Tachycardia, arrhythmias
• Paradoxical bronchospasm
• Hypokalemia (with excessive use)

Toxicity

• Overdose Symptoms:
  • Severe tachycardia, muscle cramps, seizures
  • Hypokalemia (muscle weakness, ECG changes)
• Management:
  • Beta-blockers (e.g., Propranolol) for tachycardia
  • IV fluids, potassium supplementation for hypokalemia
  • ECG monitoring and oxygen support

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3. Nursing Responsibilities for Salbutamol Inhalers

A. Patient Assessment

• Assess respiratory status before and after inhaler use (e.g., peak expiratory flow rate, oxygen saturation).
• Monitor heart rate and blood pressure, especially in cardiac patients.
• Check for signs of overuse or dependence on inhaler.

B. Proper Administration Technique

• Instruct patients on correct inhaler use:
  • Shake inhaler before use.
  • Exhale fully before inhalation.
  • Inhale deeply while pressing the inhaler.
  • Hold breath for 10 seconds, then exhale slowly.
  • Wait 1–2 minutes before taking a second puff (if needed).
• Use a spacer device in children and elderly patients to improve drug delivery.

C. Patient Education

• Do not exceed prescribed dosage (to avoid tachycardia and tremors).
• Rinse mouth after inhalation to prevent oral irritation.
• Avoid caffeine and other stimulants that may worsen palpitations.
• Recognize signs of worsening asthma (increased use of inhaler, wheezing, breathlessness).
• Use a preventive inhaler (e.g., corticosteroids) for long-term asthma control.

D. Monitoring and Documentation

• Record frequency of inhaler use (frequent use indicates poor asthma control).
• Report serious side effects or treatment failure (may need medication adjustment).

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4. Summary Table of Salbutamol Inhaler Pharmacology

Parameter	Details
Class	Short-Acting Beta-2 Agonist (SABA)
Composition	Salbutamol sulfate (100 mcg per puff)
Mechanism of Action	Stimulates β2-receptors, causing bronchodilation
Dosage & Route	Inhalation: 100–200 mcg every 4–6 hours as needed
Indications	Acute asthma, exercise-induced bronchospasm, COPD
Contraindications	Severe cardiac disease, hypertension, hyperthyroidism
Drug Interactions	Beta-blockers reduce effect; diuretics & steroids increase hypokalemia risk
Side Effects	Tremors, palpitations, headache, nervousness
Adverse Effects	Tachycardia, arrhythmias, paradoxical bronchospasm, hypokalemia
Toxicity Symptoms	Severe tachycardia, muscle cramps, seizures
Toxicity Management	Beta-blockers (for tachycardia), IV fluids, ECG monitoring

Pharmacology of Decongestants

Introduction

Decongestants are drugs used to relieve nasal congestion caused by conditions such as common cold, allergic rhinitis, sinusitis, and upper respiratory tract infections. These drugs work by reducing swelling in nasal mucosa and improving airflow through the nasal passages.

Decongestants act primarily by vasoconstriction of the nasal blood vessels, reducing inflammation and mucus production.

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1. Classification of Decongestants

A. Sympathomimetic (Adrenergic) Decongestants

• Act on α-adrenergic receptors to cause vasoconstriction, reducing nasal congestion.
• Examples: Phenylephrine, Pseudoephedrine, Oxymetazoline, Xylometazoline

B. Corticosteroid Nasal Sprays

• Reduce inflammation and swelling in nasal passages for chronic allergic rhinitis.
• Examples: Fluticasone, Budesonide, Mometasone

C. Antihistamine Combination Decongestants

• Used for allergic rhinitis and cold symptoms.
• Examples: Loratadine + Pseudoephedrine, Cetirizine + Phenylephrine

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2. Pharmacology of Commonly Used Decongestants

1. Phenylephrine (Adrenergic Nasal Decongestant)

Composition

• Phenylephrine Hydrochloride

Action

• Selective α1-adrenergic receptor agonist → Vasoconstriction of nasal mucosa → Reduced swelling and congestion.

Dosage and Route

• Oral: 10 mg every 4–6 hours (max: 60 mg/day).
• Nasal spray: 1–2 sprays per nostril every 4 hours (max: 3 days use).

Indications

• Nasal congestion (cold, sinusitis, allergic rhinitis).
• Eustachian tube dysfunction (ear congestion).

Contraindications

• Uncontrolled hypertension, cardiac diseases.
• Hyperthyroidism (risk of increased heart rate).
• Use for more than 3 days (risk of rebound congestion).

Drug Interactions

• Monoamine oxidase inhibitors (MAOIs) – Risk of hypertensive crisis.
• Beta-blockers – May reduce decongestant effect.

Side Effects

• Increased heart rate, hypertension, nervousness, headache.

Adverse Effects

• Rebound congestion (rhinitis medicamentosa) after prolonged use.
• Severe hypertension, arrhythmias (with overdose).

Toxicity

• Overdose Symptoms: Severe hypertension, tachycardia, restlessness.
• Management: Supportive care, beta-blockers for hypertension, IV fluids.

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2. Pseudoephedrine (Systemic Nasal Decongestant)

Composition

• Pseudoephedrine Hydrochloride

Action

• Non-selective α and β adrenergic agonist → Vasoconstriction + Mild bronchodilation.

Dosage and Route

• Oral: 30–60 mg every 4–6 hours (max: 240 mg/day).

Indications

• Nasal congestion in colds, flu, sinusitis, allergic rhinitis.
• Adjunct in otitis media (ear congestion).

Contraindications

• Hypertension, heart disease, hyperthyroidism.
• Glaucoma (risk of increased intraocular pressure).

Drug Interactions

• Increases risk of hypertension with MAOIs, tricyclic antidepressants.
• May reduce antihypertensive effects of beta-blockers.

Side Effects

• Increased blood pressure, insomnia, dizziness.

Adverse Effects

• Severe hypertension, cardiac arrhythmias, agitation.

Toxicity

• Overdose Symptoms: Tremors, palpitations, seizures.
• Management: Activated charcoal, IV beta-blockers, sedation if needed.

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3. Oxymetazoline (Topical Nasal Decongestant)

Composition

• Oxymetazoline Hydrochloride 0.05%

Action

• Direct α1 and partial α2 agonist → Vasoconstriction of nasal mucosa → Immediate relief of nasal congestion.

Dosage and Route

• Nasal Spray: 1–2 sprays per nostril every 10–12 hours (max: 2 doses per day).

Indications

• Short-term relief of nasal congestion in colds, sinusitis, and allergic rhinitis.

Contraindications

• Use beyond 3 days (rebound congestion).
• Hypertension, cardiovascular diseases.

Drug Interactions

• MAOIs and sympathomimetics increase hypertensive effects.

Side Effects

• Dry nose, mild stinging, sneezing.

Adverse Effects

• Rebound congestion (rhinitis medicamentosa).
• Tachycardia, elevated BP if absorbed systemically.

Toxicity

• Overdose Symptoms: Bradycardia (from α2 stimulation), hypertension.
• Management: IV fluids, symptomatic treatment.

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3. Nursing Responsibilities for Decongestants

A. Patient Assessment

• Monitor BP and heart rate before administering systemic decongestants.
• Assess nasal congestion severity and duration of symptoms.
• Check for contraindications (e.g., hypertension, glaucoma).

B. Proper Administration Technique

• For nasal sprays:
  • Shake well before use.
  • Insert nozzle into nostril while tilting the head slightly forward.
  • Spray while inhaling gently, avoid sniffing deeply.
  • Limit use to 3 days to prevent rebound congestion.

C. Patient Education

• Avoid prolonged use of nasal sprays (risk of rebound congestion).
• Do not take with other stimulants (caffeine, energy drinks).
• Report any severe side effects like palpitations, high BP.
• Avoid in pregnancy unless prescribed (risk of fetal vasoconstriction).

D. Monitoring and Documentation

• Monitor for overuse symptoms (e.g., worsening congestion).
• Document BP, HR, and response to treatment.
• Report any adverse drug reactions.

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4. Summary Table of Decongestant Pharmacology

Drug	Mechanism	Route & Dose	Indications	Side Effects	Adverse Effects	Toxicity Management
Phenylephrine	α1-Agonist → Vasoconstriction	Oral: 10 mg Q4-6h, Nasal: 1-2 sprays Q4h	Cold, sinusitis	Headache, nervousness	Rebound congestion, hypertension	Beta-blockers, IV fluids
Pseudoephedrine	α/β-Agonist → Vasoconstriction & Bronchodilation	Oral: 30-60 mg Q4-6h	Nasal congestion, otitis media	Insomnia, dizziness	Severe hypertension, arrhythmias	Activated charcoal, beta-blockers
Oxymetazoline	α1, α2 Agonist → Nasal vasoconstriction	Nasal spray: 1-2 sprays Q10-12h	Short-term nasal congestion relief	Dry nose, sneezing	Rebound congestion, BP elevation	IV fluids, symptomatic care

Pharmacology of Expectorants, Antitussives, and Mucolytics

Introduction

Expectorants, antitussives, and mucolytics are commonly used in the management of cough and respiratory conditions involving excessive mucus production, such as bronchitis, pneumonia, asthma, and chronic obstructive pulmonary disease (COPD).

• Expectorants: Help in thinning and loosening mucus for easier clearance.
• Antitussives: Suppress cough reflex, useful in dry cough.
• Mucolytics: Break down thick mucus to improve expectoration.

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1. Classification of Expectorants, Antitussives, and Mucolytics

A. Expectorants (Increase Mucus Secretion and Clearance)

• Examples: Guaifenesin, Ammonium chloride, Potassium iodide
• Action: Increase fluid secretion in airways, making mucus easier to expel.

B. Antitussives (Suppress Cough Reflex)

1. Opioid Antitussives (Act on the central nervous system)
   • Examples: Codeine, Pholcodine
2. Non-Opioid Antitussives (Peripheral or central action)
   • Examples: Dextromethorphan, Benzonatate

C. Mucolytics (Break Down Thick Mucus)

• Examples: Acetylcysteine, Carbocisteine, Bromhexine, Erdosteine
• Action: Decrease viscosity of mucus, improving expectoration.

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2. Pharmacology of Commonly Used Expectorants, Antitussives, and Mucolytics

1. Guaifenesin (Expectorant)

Composition

• Guaifenesin (Glyceryl guaiacolate)

Action

• Increases respiratory tract secretions, reducing mucus thickness.
• Facilitates mucus clearance by ciliary movement.

Dosage and Route

• Oral (Syrup/Tablets):
  • Adults: 200–400 mg every 4–6 hours (Max: 2400 mg/day).
  • Children: 100–200 mg every 4–6 hours.

Indications

• Productive cough in colds, bronchitis, pneumonia, COPD.

Contraindications

• Chronic dry cough (use antitussives instead).
• Severe renal impairment.

Drug Interactions

• Minimal interactions, safe for most patients.

Side Effects

• Nausea, dizziness, drowsiness.

Adverse Effects

• Excessive mucus production (rare).

Toxicity

• Overdose Symptoms: Nausea, vomiting, dizziness.
• Management: Supportive care, hydration.

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2. Codeine (Opioid Antitussive)

Composition

• Codeine Phosphate

Action

• Binds to opioid receptors in the brainstem, suppressing the cough reflex.

Dosage and Route

• Oral: 10–20 mg every 4–6 hours (Max: 120 mg/day).

Indications

• Dry, non-productive cough.

Contraindications

• Respiratory depression (COPD, asthma, neonates).
• History of opioid addiction.

Drug Interactions

• CNS depressants (alcohol, benzodiazepines) increase sedation risk.
• MAO inhibitors increase risk of severe respiratory depression.

Side Effects

• Drowsiness, dizziness, nausea, constipation.

Adverse Effects

• Respiratory depression, dependency, hallucinations (with long-term use).

Toxicity

• Overdose Symptoms: Severe drowsiness, hypotension, respiratory failure.
• Management: Naloxone (opioid antidote), respiratory support.

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3. Dextromethorphan (Non-Opioid Antitussive)

Composition

• Dextromethorphan Hydrobromide

Action

• Acts on the cough center in the medulla, suppressing the cough reflex.

Dosage and Route

• Oral (Syrup/Tablets):
  • Adults: 15–30 mg every 6–8 hours (Max: 120 mg/day).
  • Children: 7.5–15 mg every 6–8 hours.

Indications

• Dry, irritating cough in colds, allergies, and mild respiratory infections.

Contraindications

• Asthma, COPD, productive cough.
• MAO inhibitors (risk of serotonin syndrome).

Drug Interactions

• Antidepressants (SSRIs, MAOIs) increase serotonin syndrome risk.
• Alcohol, CNS depressants increase sedation.

Side Effects

• Dizziness, nausea, dry mouth.

Adverse Effects

• Hallucinations (at high doses, abuse potential).

Toxicity

• Overdose Symptoms: Excitation, confusion, seizures.
• Management: Supportive care, benzodiazepines for seizures.

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4. Acetylcysteine (Mucolytic)

Composition

• N-Acetylcysteine (NAC)

Action

• Breaks disulfide bonds in mucus proteins, reducing mucus viscosity.
• Acts as an antioxidant, replenishing glutathione.

Dosage and Route

• Oral: 600 mg once daily or divided doses.
• Nebulization: 3–5 mL of 10% solution every 6–8 hours.
• IV (Paracetamol overdose antidote): 150 mg/kg loading dose over 1 hour, then maintenance infusion.

Indications

• Thick mucus in chronic bronchitis, COPD, pneumonia, cystic fibrosis.
• Acetaminophen (paracetamol) overdose.

Contraindications

• Active peptic ulcer (risk of gastric irritation).
• Severe asthma (may worsen bronchospasm).

Drug Interactions

• Enhances effect of nitroglycerin (hypotension risk).

Side Effects

• Nausea, vomiting, sulfur-like smell.

Adverse Effects

• Bronchospasm, anaphylactoid reactions (IV form).

Toxicity

• Overdose Symptoms: Severe nausea, respiratory distress.
• Management: Stop medication, give bronchodilators for bronchospasm.

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3. Nursing Responsibilities for Expectorants, Antitussives, and Mucolytics

A. Patient Assessment

• Assess type of cough (productive vs. non-productive).
• Monitor lung sounds, oxygen saturation, and respiratory rate.
• Evaluate for drug contraindications (e.g., opioids in respiratory depression).

B. Proper Administration and Monitoring

• Encourage increased fluid intake to aid mucus clearance.
• Monitor for signs of toxicity, overdose, or drug dependence.
• Ensure proper nebulizer use for mucolytics (avoid eye contact with acetylcysteine).

C. Patient Education

• Expectorants: Increase water intake for better mucus clearance.
• Antitussives: Avoid alcohol, operating machinery (CNS depression risk).
• Mucolytics: Warn about initial increase in cough before mucus clearance.

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4. Summary Table of Common Drugs

Drug	Class	Mechanism	Indications	Side Effects	Toxicity Management
Guaifenesin	Expectorant	Increases mucus secretion	Productive cough	Nausea, dizziness	Supportive care
Codeine	Opioid Antitussive	Suppresses cough reflex	Dry cough	Drowsiness, constipation	Naloxone, respiratory support
Dextromethorphan	Non-Opioid Antitussive	Acts on cough center	Dry cough	Dizziness, hallucinations	Benzodiazepines for seizures
Acetylcysteine	Mucolytic	Breaks mucus bonds	Thick mucus, COPD	Nausea, bronchospasm	Bronchodilators for bronchospasm

Pharmacology of Bronchoconstrictors and Antihistamines

Introduction

• Bronchoconstrictors are agents that narrow the airways by causing contraction of smooth muscles in the bronchi, leading to difficulty in breathing, wheezing, and shortness of breath. These substances include histamines, leukotrienes, acetylcholine, and environmental allergens that trigger bronchospasm in conditions like asthma, chronic obstructive pulmonary disease (COPD), and allergic reactions.
• Antihistamines counteract the effects of histamine and are used in allergic reactions, anaphylaxis, hay fever, urticaria, and motion sickness.

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1. Classification of Bronchoconstrictors and Antihistamines

A. Bronchoconstrictors (Cause Airway Narrowing)

1. Histamines – Released from mast cells during allergic reactions.
   • Examples: Histamine (H1 receptor activation causes bronchospasm).
2. Leukotrienes – Inflammatory mediators causing bronchial smooth muscle contraction.
   • Examples: Leukotriene D4 (LTD4), Leukotriene C4 (LTC4).
3. Acetylcholine (Cholinergic Stimulators) – Acts on M3 receptors leading to bronchoconstriction.
   • Example: Methacholine (used in bronchial provocation tests).
4. Environmental Irritants – Smoke, pollutants, allergens that trigger asthma.

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B. Antihistamines (Block Histamine Receptors)

1. H1 Receptor Antagonists (For Allergic Reactions)
   • First-Generation Antihistamines (Sedating, Cross Blood-Brain Barrier):
     • Examples: Diphenhydramine, Promethazine, Hydroxyzine, Chlorpheniramine.
   • Second-Generation Antihistamines (Non-Sedating, Peripheral Action):
     • Examples: Loratadine, Cetirizine, Fexofenadine, Desloratadine.
2. H2 Receptor Antagonists (For Gastric Acid Secretion)
   • Examples: Ranitidine, Famotidine, Cimetidine (used for acid reflux, ulcers).

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2. Pharmacology of Commonly Used Bronchoconstrictors and Antihistamines

1. Histamine (Bronchoconstrictor)

Composition

• Endogenous biogenic amine released from mast cells.

Action

• Stimulates H1 receptors in the lungs → Bronchoconstriction and inflammation.
• Increases capillary permeability, leading to swelling and mucus secretion.

Dosage and Route

• Histamine challenge test for bronchial hyperreactivity:
  • Inhaled 0.03–0.25 mg/mL of histamine aerosol.

Indications

• Used in provocation tests for asthma diagnosis.

Contraindications

• Asthma, COPD (risk of severe bronchospasm).
• Anaphylaxis history.

Drug Interactions

• Worsens bronchospasm if combined with allergens.

Side Effects

• Coughing, wheezing, shortness of breath.

Adverse Effects

• Severe bronchoconstriction, anaphylaxis.

Toxicity

• Overdose Symptoms: Hypotension, respiratory distress.
• Management: Epinephrine, oxygen therapy, antihistamines.

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2. Diphenhydramine (First-Generation H1 Antihistamine)

Composition

• Diphenhydramine Hydrochloride

Action

• Blocks H1 receptors, preventing bronchoconstriction, vasodilation, and inflammation.
• Crosses blood-brain barrier, causing sedation.

Dosage and Route

• Oral: 25–50 mg every 6–8 hours (Max: 300 mg/day).
• IV/IM (Severe Allergic Reactions): 10–50 mg every 4–6 hours.

Indications

• Allergic rhinitis, anaphylaxis adjunct, urticaria, motion sickness.

Contraindications

• Glaucoma (increases intraocular pressure).
• BPH (risk of urinary retention).

Drug Interactions

• Increases sedation with alcohol, benzodiazepines.
• Enhances effects of opioids and muscle relaxants.

Side Effects

• Drowsiness, dry mouth, dizziness.

Adverse Effects

• Confusion, hallucinations (in elderly patients).
• Severe anticholinergic effects (urinary retention, blurred vision).

Toxicity

• Overdose Symptoms: Extreme drowsiness, hallucinations, seizures.
• Management: Activated charcoal, IV fluids, benzodiazepines for seizures.

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3. Loratadine (Second-Generation H1 Antihistamine)

Composition

• Loratadine

Action

• Selectively blocks H1 receptors without significant CNS penetration → No sedation.

Dosage and Route

• Oral: 10 mg once daily.

Indications

• Seasonal allergic rhinitis, chronic urticaria.

Contraindications

• Severe liver disease (metabolized in the liver).

Drug Interactions

• Erythromycin, ketoconazole increase loratadine levels.

Side Effects

• Headache, dry mouth.

Adverse Effects

• QT prolongation (rare in overdose).

Toxicity

• Overdose Symptoms: Tachycardia, dizziness.
• Management: Supportive care, ECG monitoring.

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4. Leukotrienes (Bronchoconstrictors)

Composition

• Leukotriene C4 (LTC4), Leukotriene D4 (LTD4)

Action

• Activate leukotriene receptors → Bronchoconstriction, inflammation, mucus secretion.

Indications

• Bronchial provocation tests, involved in asthma pathology.

Contraindications

• Asthma, COPD (worsens bronchoconstriction).

Drug Interactions

• Leukotriene receptor antagonists (Montelukast) block their effect.

Side Effects

• Increased mucus production, airway hyperresponsiveness.

Adverse Effects

• Severe bronchospasm, hypoxia in asthma.

Toxicity

• Overdose Symptoms: Severe dyspnea, respiratory failure.
• Management: Oxygen therapy, leukotriene inhibitors (Montelukast).

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3. Nursing Responsibilities for Bronchoconstrictors and Antihistamines

A. Patient Assessment

• Assess history of asthma, COPD, and allergies before antihistamine use.
• Monitor respiratory function after exposure to bronchoconstrictors.
• Check ECG in patients using antihistamines (risk of QT prolongation).

B. Proper Administration and Monitoring

• Give first-generation antihistamines at bedtime (sedation risk).
• Monitor for paradoxical CNS stimulation in elderly patients.
• Avoid histamine-releasing foods (cheese, wine) in sensitive patients.

C. Patient Education

• Avoid driving after first-generation antihistamines.
• Use a second-generation antihistamine for daily allergy management.
• Recognize signs of antihistamine overdose (hallucinations, rapid heart rate).

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4. Summary Table of Bronchoconstrictors and Antihistamines

Drug	Class	Mechanism	Indications	Side Effects	Toxicity Management
Histamine	Bronchoconstrictor	H1 activation	Bronchial provocation test	Wheezing, dyspnea	Epinephrine, oxygen therapy
Diphenhydramine	H1 Antihistamine (1st gen)	Blocks H1 receptors	Allergy, motion sickness	Drowsiness, dry mouth	IV fluids, benzodiazepines for seizures
Loratadine	H1 Antihistamine (2nd gen)	Blocks peripheral H1	Allergic rhinitis	Headache, dry mouth	Supportive care, ECG monitoring
Leukotrienes	Bronchoconstrictor	Activates leukotriene receptors	Asthma pathophysiology	Airway inflammation	Montelukast, oxygen therapy

Role of Nurse in the Administration of Drugs Acting on the Respiratory System

Introduction

The respiratory system is responsible for oxygen exchange and removing carbon dioxide. Respiratory disorders such as asthma, chronic obstructive pulmonary disease (COPD), pneumonia, tuberculosis, and allergic reactions require pharmacological intervention.

Drugs acting on the respiratory system include bronchodilators, anti-inflammatory agents, mucolytics, expectorants, antitussives, decongestants, antihistamines, and respiratory stimulants.

Nurses play a vital role in administering, monitoring, and educating patients about respiratory drugs, ensuring safe and effective therapy.

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1. Nursing Responsibilities in Respiratory Drug Administration

A. Patient Assessment Before Drug Administration

• Assess respiratory status (rate, depth, breath sounds, oxygen saturation).
• Check vital signs (BP, heart rate, respiratory rate).
• Monitor for symptoms (wheezing, shortness of breath, productive or non-productive cough).
• Assess history of allergies and contraindications.
• Monitor peak expiratory flow rate (PEFR) in asthma patients.

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2. Nursing Role in the Administration of Specific Respiratory Drugs

A. Bronchodilators (Relieve Airway Obstruction)

1. Beta-2 Adrenergic Agonists (e.g., Salbutamol, Terbutaline, Salmeterol)

Nursing Responsibilities:

• Administer short-acting beta agonists (SABAs) for acute bronchospasm and long-acting beta agonists (LABAs) for maintenance therapy.
• Ensure proper inhaler technique (shake inhaler, deep inhalation, hold breath for 10 sec).
• Monitor for side effects: Tachycardia, tremors, palpitations.
• Educate patients:
  • SABAs are for acute relief, not for long-term control.
  • Avoid excessive caffeine intake (may worsen palpitations).

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2. Anticholinergics (e.g., Ipratropium, Tiotropium)

Nursing Responsibilities:

• Administer via inhalation to prevent bronchospasm in COPD and asthma.
• Monitor for dry mouth, blurred vision, urinary retention.
• Teach patients:
  • Rinse mouth after use to prevent oral dryness.
  • Do not swallow capsules (Tiotropium is for inhalation only).

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3. Methylxanthines (e.g., Theophylline, Aminophylline)

Nursing Responsibilities:

• Monitor serum theophylline levels (therapeutic range: 10–20 mcg/mL).
• Assess for toxicity symptoms: Seizures, tachycardia, nausea.
• Avoid giving with caffeine (risk of CNS stimulation).

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B. Anti-Inflammatory Agents (Reduce Airway Inflammation)

1. Corticosteroids (e.g., Budesonide, Fluticasone, Prednisolone)

Nursing Responsibilities:

• Monitor for side effects: Oral thrush, hoarseness, osteoporosis.
• Educate patients:
  • Rinse mouth after use to prevent fungal infections.
  • Do not stop abruptly (risk of adrenal insufficiency).
  • Use daily for asthma control, not for acute attacks.

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2. Leukotriene Receptor Antagonists (e.g., Montelukast, Zafirlukast)

Nursing Responsibilities:

• Administer orally in the evening for asthma control.
• Monitor for mood changes, suicidal thoughts (rare side effect).
• Educate patients:
  • Not for acute asthma attacks.
  • Report mood disturbances.

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3. Mast Cell Stabilizers (e.g., Cromolyn Sodium, Nedocromil)

Nursing Responsibilities:

• Administer before exposure to allergens (preventive therapy).
• Monitor for throat irritation and cough.
• Educate patients:
  • Takes 2–4 weeks for full effect.

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C. Mucolytics and Expectorants (Thin and Remove Mucus)

1. Mucolytics (e.g., Acetylcysteine, Carbocisteine)

Nursing Responsibilities:

• Use nebulized form for thick mucus conditions (COPD, bronchiectasis).
• Monitor for bronchospasm (may need bronchodilator pre-treatment).
• **Warn patients about the unpleasant sulfur odor.

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2. Expectorants (e.g., Guaifenesin, Ammonium Chloride)

Nursing Responsibilities:

• Encourage increased fluid intake to aid mucus clearance.
• Monitor for dizziness and nausea.
• Educate patients:
  • Drink plenty of fluids to help loosen mucus.
  • Used for productive cough, not for dry cough.

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D. Antitussives (Suppress Cough)

1. Opioid Antitussives (e.g., Codeine, Pholcodine)

Nursing Responsibilities:

• Monitor for drowsiness, respiratory depression, and constipation.
• Avoid in patients with COPD and sleep apnea.
• Educate patients:
  • Do not drive or operate machinery.

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2. Non-Opioid Antitussives (e.g., Dextromethorphan, Benzonatate)

Nursing Responsibilities:

• Monitor for dizziness and hallucinations (high doses).
• Avoid combining with MAO inhibitors (risk of serotonin syndrome).

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E. Decongestants (Reduce Nasal Congestion)

1. Adrenergic Decongestants (e.g., Phenylephrine, Pseudoephedrine, Oxymetazoline)

Nursing Responsibilities:

• Monitor for hypertension and tachycardia.
• Limit nasal spray use to 3 days (risk of rebound congestion).
• Educate patients:
  • Do not take with MAO inhibitors (risk of hypertensive crisis).

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F. Antihistamines (Block Histamine Receptors)

1. First-Generation (e.g., Diphenhydramine, Promethazine)

Nursing Responsibilities:

• Monitor for sedation, dizziness, and dry mouth.
• Avoid in elderly patients (risk of confusion, falls).

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2. Second-Generation (e.g., Loratadine, Cetirizine, Fexofenadine)

Nursing Responsibilities:

• Preferred for daily allergy treatment (less sedation).
• Monitor for headache and mild drowsiness.

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G. Respiratory Stimulants (Improve Breathing in Apnea)

1. Doxapram (Respiratory Stimulant)

Nursing Responsibilities:

• Administer IV for respiratory depression (post-anesthesia, drug overdose).
• Monitor respiratory rate and blood pressure.

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3. Summary Table of Nursing Responsibilities for Respiratory Drugs

Drug Class	Examples	Key Nursing Responsibilities	Patient Education
Bronchodilators	Salbutamol, Ipratropium	Monitor HR, teach inhaler use	Avoid overuse, rinse mouth
Corticosteroids	Budesonide, Prednisolone	Prevent thrush, taper dose	Rinse mouth, use daily
Mucolytics	Acetylcysteine	Watch for bronchospasm	Increase fluid intake
Expectorants	Guaifenesin	Encourage hydration	Used for wet cough
Antitussives	Codeine, Dextromethorphan	Monitor sedation	Avoid alcohol
Decongestants	Pseudoephedrine	Check BP, limit use	Avoid MAOIs
Antihistamines	Loratadine, Diphenhydramine	Watch for drowsiness	Avoid driving