Respiratory Drugs Flashcards
Beta-2 Agonist Examples
Salbutamol
Salmeterol
Formoterol
Terbutaline
Beta-2 Agonist Indications
- Asthma
- COPD
- Hyperkalaemia
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
Beta-2 agonist contraindications
May cause tachycardia - caution in cardiac disease as can promote angina / arrhythmias
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.
Beta-2 agonist interactions
Beta-blockers: efficacy reduced
Corticosteroids: hypokalaemia
Antimuscarinic examples
Tiotropium, Ipratopium
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
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
Antimuscarinincs contraindications
Caution in patients with:
- Angle-closure glaucoma: increase IOP
- Arrhythmias
Antimuscarinics side effects
Dry mouth
Antimuscarinics interactions
None as have low systemic absorption
Corticosteroids examples
Prednisolone, hydrocortisone, dexamethasone
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
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
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
- History of peptic ulcer, as may disrupt gastric mucosal barrier
- First trimester of pregnancy
Mucolytics side effects
Mostly rare.
- GI bleed
- Eryhtmea multiforme
- 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
- Relaxes smooth muscle of bronchial airways: inhibits enzyme responsible for breaking down cAMP –> muscle relaxation = bronchodilation
- 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
- Metabolised by CP450 enzymes - concentration increased by inhibitors and decreased by inducers. Narrow therapeutic index.
- Hypokalaemia if combined with Beta-2 agonists, so caution required in severe asthma.
Oxygen indications
- Increase tissue oxygen delivery in states of hypoxaemia.
- Accelerate reabsorption of pleural gas in pneumothorax
- Reduce half-life of carboxyhaemoglobin in carbon monoxide poisoning
Oxygen MOA
- Hypoxaemia: increases Pao2 in alveolar gas, so more o2 diffuses into blood, allowing more o2 to be delivered to tissues while underlying cause corrected.
- 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.
- CO poisoning: oxygen competes CO to bind haemoglobin - shortens half life of carboxyhaemoglobin
Oxygen administration
- Reservoir / non-rebreathe mask: bag continuously filled at 15L/min. Critical illness with sats <85%.
- Venturi mask: blends oxygen with air at fixed ratio, used for COPD patients
- Nasal cannulae: variable concentration (24-50%), at a flow of 2-6L/ min.
- 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.
