Respiratory Drugs

What receptors are stimulated by adrenaline on bronchial smooth muscle?

B2-adrenoceptors

What drug class target those receptors?

B2-adrenergic receptor agonists

Name the two types of B2-adrenergic receptor agonists and give examples

Fast acting/quick relief → Salbutamol, Formoterol
LABA → Salmeterol, Formoterol

What is the mechanism of action of B2-adrenergic receptor agonists? 3 points

Cause bronchodilation

Stabilize mast cells and inhibit inflammatory mediator release

Enhanced mucocillary clearance

What are some effects of B2-adrenergic receptor agonists?

Hypoxemia: V/Q mismatch

Tachycardia

Skeletal muscle tremor

Hypokalemia

Mechanism of tolerance to inhaled B2-adrenergic receptor agonists

Decrease in number of receptors with prolonged use of agonist drugs.

Down regulation of adrenergic receptors in inflammatory cells.

What receptors are stimulated by acetylcholine on bronchial smooth muscle?

M3 receptors

What drug class target those receptors?

Muscarinic acetylcholine receptor antagonists

Name the two types of Muscarinic acetylcholine receptor antagonists and give examples

Fast acting ‘reliever’ → Ipratropium
Long acting ‘preventer’ → Tiotropium

What is the mechanism of action of Muscarinic acetylcholine receptor antagonists? 3 points

Bronchodilation by antagonizing action of Ach from vagus nerve.

Decreased mucus secretion

Increased mucociliary clearance

Adverse effects of Muscarinic acetylcholine receptor antagonists

Dry mouth

Blurred vision

Paradoxical bronchoconstriction

Urinary retention

What is the receptor target of Methylxanthines

Adenosine receptors

Adverse effects of Methylxanthines (Theophylline)

Cardiovascular effects
Hypokalemia

CNS stimulation

Gastrointestinal disturbances

What is the mode of action of corticosteroids?

From adrenal cortex → cortisol

Diffuse into the cytoplasm and bind to receptors

Move to nucleus to modify transcription

Increase anti-inflammatory

Decrease pro-inflammatory mediators (e.g TH2 cytokines)

Adverse reactions of corticosteroids

Adrenal suppression
Osteoporosis
Cushings syndrome
Suppression of response to infection
GI upset
Hypertension

Treatment choice for asthma?

B2 adrenergic agonists (salbutamol and salmeterol)
Combined with anti-inflammatory e.g inhaled corticosteroid

An asthmatic student has an asthma attack. They try and use their blue asthma inhaler but get no effect. They are given oxygen and a nebulizer with salbutamol.

When asked later if they had taken any other drugs they said they were given propranolol because they had been very anxious.

Why didn’t their inhaler work?

Propranolol is a non-selective beta-blocker with blocks B2-adrenergic receptors in bronchial smooth muscle.

Salbutamol is a beta-2-agonists and works by stimulating B2 receptors to relax smooth muscle and open the airways.

Taking the propranolol antagonized the action of salbutamol, reducing or completely blocking its broncho dilatory effect.

A patient has been taking their blue asthma inhaler twice a day for the last few weeks and find that is no longer working well.

What other class of drugs should they be given.

What would you need to explain them regarding onset of action of the drug.

Why is this class of drug given as an inhaler rather than a tablet?

They should be given an inhaled corticosteroid like fluticasone.

This is a preventer medication that reduces inflammation and helps control asthma long-term. Salbutamol is a reliever used for immediate relief.

They should know that inhaled corticosteroid does not provide immediate relief and works by reducing inflammation over time so they must be taken daily - even when the patient feels well. It may take several days to a few weeks to feel a noticeable improvement in symptoms.

Inhaled corticosteroids need an inhaler to:

• Deliver medication directly to the lungs.

• Lower dose compared to tablets

• Minimize synthetic side effects.

What drugs are used to treat COPD?

Muscarinic ACH receptor antagonists
Long-acting bronchodilators

Oxygen therapy

What are leukotriene antagonist and give examples

Antagonists to leukotriene receptors
Montelukast, Zafirlukast

What do they do?

Decrease bronchoconstriction, vascular permeability and mucus production as well as eosinophil recruitment.

What are leukotriene antagonists used to treat?

Preventative for asthma
Seasonal allergic rhinitis