Respiratory Drugs Flashcards by Rachel Anderson

Beta-2 Agonist Examples

Salbutamol
Salmeterol
Formoterol
Terbutaline

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Beta-2 Agonist Indications

Asthma
COPD
Hyperkalaemia

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Beta-2 Agonist mechanism of action

Beta-2 receptors found in smooth muscle of bronchi, GIT, uterus and blood vessels.

Agonisation leads to smooth muscle relaxation - improves airflow.

Stimulates Na+/K+ pumps on cell surface membranes, causing K+ to move into cell

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Beta-2 agonist contraindications

May cause tachycardia - caution in cardiac disease as can promote angina / arrhythmias

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Beta-2 agonist side effects

Stimulates sympathetic “fight or flight response” = tachycardia, palpitations, anxiety, tremor. Promote glycolysis = increased glucose.

Long-acting can produce muscle cramps.

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Beta-2 agonist interactions

Beta-blockers: efficacy reduced

Corticosteroids: hypokalaemia

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Antimuscarinic examples

Tiotropium, Ipratopium

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Antimuscarinic indications

COPD: short-acting relieves SOB, long-acting prevents SOB and exacerbations.
Asthma: short-acting adjunct during acute exacerbation, long-acting added to high-dose inhaled corticosteroids and beta-2 agonists in step 4 of treatment ladder

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Antimuscarinic mechanism of action

Competitively inhibit acetylcholine at muscarinic receptor. Muscarinic receptors stimulate parasympathetic system. Receptor blockade =

increased heart rate
smooth muscle relaxation (bronchodilation)
reduce glandular secretions in resp and GI tracts
relax pupillary constrictor = dilated pupils
relax ciliary muscles = prevents accomodation reflex

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Antimuscarinincs contraindications

Caution in patients with:

Angle-closure glaucoma: increase IOP
Arrhythmias

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Antimuscarinics side effects

Dry mouth

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Antimuscarinics interactions

None as have low systemic absorption

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Corticosteroids examples

Prednisolone, hydrocortisone, dexamethasone

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Corticosteroids indications

Allergic / inflammatory disorders: asthma, anaphylaxis
Suppression of autoimmune disease: IBD, arthritis
Cancer treatment - as part of chemo or to reduce tumour swelling
Hormone replacement in adrenal insufficiency or hypopituartism

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Coricosteroid mechanism of action

Mostly glucocorticoid effects:
Modify the immune response
Up-regulate anti-inflammatory genes
Down-regulate pro-inflammatory genes e.g. cytokines, TNF-alpha
Suppress eosinophils and monocytes
Increase gluconeogenesis

Some mineralocorticoid effects:

Stimulate Na+ and water retention
Promote K+ and H+ excretion

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Corticosteroid administration

Systemic: oral, IV, IM

Acute asthma: oral, 40mg daily

Corticosteroids Contraindications

Caution in:

Infection
Children - suppress growth

Corticosteroids side effects

Immunosuppression: risk and severity of infection and alters host response
Metabolic effects: DM, osteoporosis
Increased catabolism: proximal muscle weakness, skin thinning, easy bruising, gastritis
Mood changes: insomnia, confusion, psychosis, suicidal ideation
Mineralocorticoid: hypertension, hypokalaemia, oedema
Adrenal atrophy as suppresses ACTH secretion, switching off stimulus for normal adrenal cortisol production.
Sudden withdrawal = Addisonian crisis with cardiovascular collapse.
Symptoms of chronic glucocorticoid withdrawal include fatigue, weight loss and arthralgia.
Cushing’s sydnrome

Corticosteroid interactions

NSAIDs: Increase risk of peptic ulceration and GI bleed
Enhance hypokalaemia: beta-2 agonists, theophylline, loop or thiazide diuretics.
Cytochrome P450 inducers may reduce efficacy
Reduce immune response to vaccines

Corticosteroids patient information

Take in morning to mimic circadian rhythm.

Mucolytics examples

Carbocisteine

Mucolytics indications

COPD and Bronchiectasis - reduction of sputum viscosity

Mucolytics MOA

Reduces goblet cel hyperplasia therefore reducing amount and viscosity of mucus glycoprotein secreted by respiratory tract

Mucolytics adminisatration

Oral

Mucolytics contraindications

1. History of peptic ulcer, as may disrupt gastric mucosal barrier 2. First trimester of pregnancy

Mucolytics side effects

Mostly rare. 1. GI bleed 2. Eryhtmea multiforme 3. Stevens-Johnson syndrome

Mucolytics interactions

Should not be used with antitussives (cough suppressants) or medicines that dry up bronchial secretions

Theophylline indications

Asthma and COPD - treatment of symptoms

Theophylline MOA

1. Relaxes smooth muscle of bronchial airways: inhibits enzyme responsible for breaking down cAMP --> muscle relaxation = bronchodilation 2. Reduces airway response to hisatmine / methacholine / adenosine and allergens. Prevents bronchoconstriction.

Theophylline administration

Oral

Theophylline contraindications

Narrow therapeutic index. Caution in cardiac and hepatic failure and viral infections as concentration increased. Concentration decreased in smokers and alcohol consumption.

Theophylline side effects

Arrhythmias, tachycardia + palpitations, CNS stimulation, convulsions, GI upset, headache, insomnia

Theophylline interactions

1. Metabolised by CP450 enzymes - concentration increased by inhibitors and decreased by inducers. Narrow therapeutic index. 2. Hypokalaemia if combined with Beta-2 agonists, so caution required in severe asthma.

Oxygen indications

1. Increase tissue oxygen delivery in states of hypoxaemia. 2. Accelerate reabsorption of pleural gas in pneumothorax 3. Reduce half-life of carboxyhaemoglobin in carbon monoxide poisoning

Oxygen MOA

1. Hypoxaemia: increases Pao2 in alveolar gas, so more o2 diffuses into blood, allowing more o2 to be delivered to tissues while underlying cause corrected. 2. Pneumothorax: reduces fraction on nitrogen in alveolar gas - accelerates diffusion of nitrogen out of body. Pleural air composed mainly of nitrogen, meaning it is reabsorbed faster. 3. CO poisoning: oxygen competes CO to bind haemoglobin - shortens half life of carboxyhaemoglobin

Oxygen administration

1. Reservoir / non-rebreathe mask: bag continuously filled at 15L/min. Critical illness with sats <85%. 2. Venturi mask: blends oxygen with air at fixed ratio, used for COPD patients 3. Nasal cannulae: variable concentration (24-50%), at a flow of 2-6L/ min. 4. Simple facemask - few advantages

Oxygen Side effects

``` Mask discomfort Dry throat (lack of water vapour) - improved by using humidification system ```

Oxygen contraindications

In chronic type 2 respiratory failure (severe COPD), there are adaptive changes to persistent hypoxaemia and hypercapnia. If exposed to high O2 concentrations, adaptive state disturbed, causing rise in blood Co2. This leads to respiratory acidosis, depressed consciousness and worsened hypoxia. Aim for 88-92% saturations in these patients.