Drugs used to treat asthma & drugs affecting the respiratory system (L12) Flashcards
regulation of respiration
spontaneous rhythmic discharge
voluntary control
autonomic regulation
parasympathetic activation
bronchial and vascular smooth muscle and glands
M3 cholinergic receptors
stimulation results in bronchoconstriction and increased mucus secretions
sympathetic activation
adrenergic regulation
circulating adrenaline from the adrenal medulla acts on B2 receptors on chronicle smooth muscle
smooth muscle relaxation and bronchodilation
NANC innervation
nonadrenergic noncholinergic
inhibitory:
• NO on bronchial smith muscle
• smooth muscle relaxation and bronchodilation
excitatory:
• substance P, neurokinin A
• smooth muscle contraction and bronchoconstriction
disorders of respiratory function
asthma
cough
what is asthma?
recurrent reversible obstruction of the airways in response to stimuli which are not themselves noxious and do not cause the syndrome in non-asthmatics
pathology of asthma
acute airway obstruction caused by contraction of the airway smooth muscle
mucus hyper secretion and thickening
airway inflammation
symptoms of asthma
dyspnea
wheezing
coughing
2 phases of asthma
immediate phase
• bronchoconstriction on exposure to stimuli
late/delayed phase
• inflammation/damage in response to inflammatory mediators
immediate phase
bronchospasm
interaction with mast cells
• release of spasmogens - histamine and leuktreines
• bronchospasm
• release chemotaxis, LTB4 attraction of leukocytes
late phase
inflammation and hypertension
influx of cytokines releases lymphocytes and eosinophils
• long lasting damage to epithelium of bronchial tissue
• hyperactivity of bronchial tissue
what do asthma drugs do?
aim to prevent the release of bronchospasm from mast cells
what are some bronchodilators?
beta2 agonists
muscarininc (M) antagonists
xanthines
what do beta2 agonists do?
dilate bronchi
inhibits mediator released from mast cells
given by inhalation:
• short acting - salbutamol
• long lasting - salmeterol
side effects:
• tolerance
• tremor
action of salbutamol/salmeterol on beta2 adrenoreceptors
1) salbutamol/salmeterol acts on the receptor
2) activates adenyl cyclase
3) increase cAMP
4) smooth muscle relaxation
5) bronchodilation
6) it them dissipates from receptor
how is salmeterol different from salbutamol?
has a large lipophilic chain attached
when it dissociate it doesn’t go far as it is still attached to cell membrane
it doesn’t get metabolised as quickly as salbutamol which means they have different half lives
what do muscarinic antagonists do?
dilate bronchi
• block M3 mediated bronchoconstriction
decrease mucus secretion
eg. ipratropium
• given by inhalation
• relatively non-selective but not well absorbed
what do xanthines do?
bronchodilator
• block phosphodiesterase III and IV increasing cAMP leading to bronchodilation
anti-inflammatory properties
eg. theophylline
• well absorbed orally
• narrow therapeutic window
drugs used to treat bronchospasm
chromolyn
beta2 agonist
M antagonist
xanthines
glucocorticoids
what do glucocorticoids do?
effective in the treatment of the delayed phase
suppress the inflammatory response
• induces synthesis of lipocortin which inhibits phospholipase A2 so decreases production of inflammatory mediators
side effects:
• oral thrush
• cushings syndrome
chromolyn
mast cell stabiliser
• prevents release of histamine and inflammatory mediators
most recent drug used to treat asthma
cysteine-leukotriene (CysLT1) receptor antagonist
cysteine-leukotriene (CysLT1) receptor antagonist
treats both phases
effective for mild-persistent asthma
non as effective as glucocorticoids - not as many side effects
what is a cough?
reflex triggered by mechanical or chemical stimulation of the upper respiratory tract
serves to expel foreign bodies and unwanted material from the airways
regulation of cough
sensor components
central components - cough centre in hypothalamus
intercostal and phrenic nerves regulating respiratory muscle
drugs used in the reduction of sensory receptor sensitivity of cough
menthol vapour
eucalyptus oil
topical local anaesthetics - benzococaine and cocaine
drugs that target the cough centre in the brain
regulated by opioid receptors
opiod receptor agonists
eg. codeine and dextromethophan
