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Overview of Nervous Systems and Drug Classifications

  • The nervous system is classified into two main parts:

    • Sympathetic Nervous System (SNS)

    • Activates 'fight or flight' responses.

    • Increases heart rate, dilates airways (bronchodilation).

    • Parasympathetic Nervous System (PNS)

    • Activates 'rest and digest' responses.

    • Decreases heart rate, causes bronchoconstriction.

Bronchodilators

  • Bronchodilators are primarily used to stimulate the sympathetic nervous system.

    • They promote bronchodilation to relieve symptoms of respiratory conditions.

  • Common bronchodilators include:

    • Albuterol (short-acting beta agonist, SABA)

    • Targets beta-2 adrenergic receptors in the lungs.

    • Mechanism: Stimulates beta-2 receptors causing relaxation of bronchial smooth muscle, leading to bronchodilation.

    • Zopanex can also be classified similarly as a beta-2 agonist.

    • Albuterol is more specific for beta-2, while some may target alpha and beta-1 receptors as well.

Anticholinergic Drugs

  • Anticholinergic drugs work by blocking the actions of the parasympathetic nervous system.

    • They prevent bronchoconstriction by inhibiting acetylcholine from binding to its receptors.

  • Role in COPD:

    • Common for COPD patients to use these drugs.

    • While SABAs provide quick relief, they do not last long, so longer-acting agents are used for maintenance.

    • Long-acting agents are often combined with anticholinergics for sustained airflow.

  • Example of anticholinergic medication:

    • Ipratropium Bromide:

    • Derived from atropine, delivered via metered-dose inhaler (MDI) or nebulizer.

    • Synergistic effect: When combined with albuterol, enhanced bronchodilation occurs.

    • Commercial names include DuoNeb (nebulizer) and Combivent (MDI).

    • Glycopyrrolate:

    • Primarily used to reverse neuromuscular block and has off-label use in aerosol form to reduce secretions.

    • Caution: Not suitable for patients with thick sputum.

    • Tiotropium Bromide (Spiriva):

    • Administered in a dry powder form for long-term control.

Mechanism of Action

  • Both bronchodilators and anticholinergics interact with the nervous system differently:

    • Beta-2 agonists activate bronchodilation via the sympathetic pathway.

    • Anticholinergics block signals from the parasympathetic nervous system, thus preventing bronchoconstriction.

  • Relationship to neurotransmitters:

    • PNS primarily utilizes acetylcholine (for bronchoconstriction and secretions).

    • SNS utilizes norepinephrine (for bronchodilation).

Clinical Applications

  • COPD Management:

    • Regular use of ipratropium and albuterol can improve pulmonary function tests (PFTs), particularly the FEV1 % ratio.

  • Asthma Context:

    • Anticholinergics may be used in specific asthma scenarios, e.g., nocturnal asthma or in patients on beta-blockers, though primarily meant for COPD management.

    • Combination therapies can enhance results.

  • Administration Protocol:

    • Administer beta agonists first for rapid bronchodilation, followed by anticholinergics to maintain open airways.

    • Monitor response pre- and post-treatment through breath sounds, assessment of peak flow rates, and patient feedback.

Side Effects and Considerations

  • Anticholinergics are known as antimuscarinics and may cause various side effects beyond respiratory effects, including pupil dilation and potential effects on the cardiac and gastrointestinal systems.

  • When using these medications, awareness of their focused action on the lungs and minimizing systemic effects is crucial.

Closure

  • The next session will involve evaluating understanding with a quiz covering the nervous systems, pharmacology terminology, and specifics of bronchodilators and anticholinergics.

  • Emphasis on continuous learning and engagement with clinical experiences is provided.

  • Encourage exploring various clinical scenarios to enhance learning and decision-making in respiratory therapy.

Practical Lessons

  • Case Study Discussion:

    • A serious incident involving tracheostomy management illustrates the importance of alertness and knowledge in emergency situations.

    • Highlighting the potential for airway complications and the necessity of understanding airway anatomy and physiology.

Key Reminders

  • Focused study of the pharmacology modules is essential for success, including ongoing clinical experiences.

  • Maintaining a balance between study and rest is vital for effective learning and retention.