Lesson 121- respiratory disease drugs

Lesson Overview

Topic: General treatment concepts of common respiratory diseasesInstructor: Arno H. Werners, DVM MEd PhD DECVPTContact: awerners@sgu.edu

Learning Objectives

  • Define therapeutic goals in animals with respiratory diseases, emphasizing the importance of improving quality of life and minimizing symptoms.

  • Identify therapeutic targets in animals with respiratory diseases, including pharmacological and non-pharmacological interventions.

  • Compare indications, mechanisms, therapeutic effects, and adverse effects of various drugs used in respiratory disease treatment, facilitating informed decision-making.

Case Study: German Shorthair Pointer

Patient Profile: 4-year-old intact femaleContext: Linked to exercise and excitement; recently boarded, leading to potential stress-related reactions.Question: What is the therapeutic goal?

Pathogenesis of Respiratory Diseases

Causes of Respiratory Diseases:

  • Pathogens: Identifying the role of bacteria, viruses, parasites, and fungi in initiating respiratory diseases.

  • Immune-mediated: Examining allergies and immune responses, exemplified by allergens causing conditions such as asthma in various animals.

  • Toxicities: Investigating the impact of environmental pollutants and irritants on airway health.

  • Neoplasia: Distinguishing between primary tumors and metastatic disease affecting the respiratory system.

Common Respiratory Diseases

  1. Respiratory Infections:

    • In-depth analysis of bacterial, viral, fungal, and parasitic infections and their specific treatments.

  2. Allergic Responses:

    • Exploring allergic rhinitis in dogs, and asthma presentations specifically in cats and horses, including triggers and management strategies.

Pathophysiological Changes

Consequences of Respiratory Diseases:

  • Infection leading to complications like pneumonia.

  • Irritation of airways causing coughing and significant discomfort.

  • Inflammation and bronchoconstriction, influencing airflow and gas exchange negatively.

  • Destruction of epithelial cells, leading to pus accumulation and excess mucus production, complicating respiratory function.

Treatment of Respiratory Infections

Bacterial Infection Management:

  • Importance of determining if the infectious agent is known (whether single or multiple isolates present).

  • Tailoring antibiotic choice according to infection location and the calculable volume of distribution for optimal effect.

Clinical Cases

  • Example 1: Foal with pneumonia

    • Symptoms: Fever, labored breathing, cough.

    • Diagnosis: Positive culture for Rhodococcus equi, necessitating specific antimicrobial therapy.

  • Example 2: Calves with respiratory disease

    • Symptoms: Nasal discharge, increased respiratory effort, gauntness, and fever.

    • Diagnosis: Identified with Bovine Respiratory Disease Complex, requiring a multifaceted treatment approach.

Cough Classification

Types of Cough:

  • Purposeful: A protective cough beneficial for expelling material, crucial in presentations of bacterial pneumonia.

  • Warning: Cough as an indicator of serious conditions, such as pulmonary edema, necessitating urgent care.

  • Nuisance: Cough that is chronic and unnecessary, requiring suppression (e.g. chronic bronchitis) to enhance patient comfort.

Treatment Targets for Cough Reflex

Receptor Considerations:

  • NK receptor antagonists, Opioids: (e.g., hydrocodone, codeine) for effective cough control.

  • Sodium channel blockers: (e.g., lidocaine) for their analgesic properties and potential to provide relief.

Inflammation Management in Airways

Drug Groups for Inflammation Treatment:

  • COX-1 and COX-2 inhibitors: Non-steroidal anti-inflammatory drugs (NSAIDs) aimed at reducing inflammation.

  • Steroids: Corticosteroids used for their potent anti-inflammatory effects.

  • Leukotriene antagonists: Targeting specific pathways involved in allergic reactions and inflammatory responses.

Specific Case: Boxer Dog with Rhinitis

Symptoms: Nasal discharge, epistaxis, breathing problems.

  • Diagnosis: Idiopathic lympho-plasmacytic rhinitis requiring a tailored therapeutic approach.

  • Goals: Establish clear therapeutic objectives and the appropriate drug classes for treatment.

  • Glucocorticosteroids: Utilized for their efficacy in managing inflammation across various animal types.

Indications by Animal Type:

  • Cats: Effective management of feline asthma through appropriate corticosteroid use.

  • Dogs: Chronic bronchitis treatments such as prednisone and fluticasone to control inflammation.

  • Horses: Management of equine asthma through targeted therapeutic strategies.

Bronchodilation Treatment Options

Receptive Actions:

  • β2-agonists: (e.g., terbutaline, albuterol) used to relax bronchial smooth muscle and improve airflow.

  • Muscarinic antagonists: Helping to reduce airway resistance and ease breathing in asthmatic cases.

  • Adverse Effects: Notable effects include excitement, increased heart rate, and sweating in horses requiring careful monitoring.

Methylxanthines as Bronchodilators

Primary Drug: Theophylline (oral administration) is effective but requires monitoring for side effects.

  • Adverse Effects: Include nausea, cardiac stimulation, and CNS effects, emphasizing the need for dosage regulation.

Conclusion and Key Takeaways

  • Therapeutic Strategy: Must be tailored based on the unique pathophysiology of respiratory diseases in individual patients.

  • Pharmacokinetic Requirements: Critical for ensuring the correct antibiotic choice in treating lung infections effectively.

  • Asthma Management: Requires consideration of multi-drug therapeutic strategies for effective long-term control of chronic respiratory conditions.