Drugs used in asthma and COPD- beta-2-agonist Flashcards
how are b2 agonists split into?
dependants on their length of action, short and long acting
what are the 2 types of short acting drugs?
salbutamol and terbutaline
how long does it take to get maximum affect for a short acting b2 agonist?
30 mins for maximum and broncodilatery effects last about 4-6 hours
how do b2 agonists work?
having a direct effect on b2 receptors in the airways causes the rapid broncodilation patients require when experiencing symptoms or breathlessness.
why cant the long action b2 agonsits be used with a patient experiencing acute symptoms?
no rapid onset of broncodilators
why is formoterol an anomaly?
because it is both a long and short acting b2 agonist with dual action
which b2 agonists can ony be used for COPD?
indacaterol, olodaterol, vilanterol
what b2 agonists are used for long action?
indacaterol, olodaterol, vilanterol, salmerterol, formoterol, bambuterol
what b2 agonists are long acting that are available for asthma?
salmeterol and bambuterol
what doseage form does bambuterol come in ?
as an oral tablet, its rarer in practise as it is a prodrug of terbutaline.
what are some adverse effects of b2 agonists for systemic absorption?
- tremors
- nervous tension
- headache
- tachycardia/palpitations
- hypokalaemia
what percentage of the drug reaches the airways using an inhaled method?
10-20%, rest is deposited and then swallowed
Why may adverse effects occur?
When higher doses are being used
When may a patient be given a b-anatagonist?
If they have CV disease
What are some counselling points for short acting medications?
- reliever/rescue therapy
- carry all the time
- use before exercise
- doses per day use max salbutamol 8 times
- follow advice on hoe to take it
What are some counselling points for long acting medication?
- preventer therapy
- take regularly
What is MART therapy for asthma?
Uses formoterol and steroid combination, formoterol has both short and long acting components usually taken BD as preventer or used sometimes as rescue, has a rapid bronchodilater affect
What does LABA mean?
Long acting b2 agonist
What the difference between salbutamol and salmeterol with binding to active sites?
Salbutamol bind to the active site of the b2-adrenoreceptor but salmeterol will bind within the active site but with the exo-site
What type of cells are b2 adrenergic receptors?
G-protein couple receptors
Where does the b2 receptor bind to on the g protein?
B2 receptors couple with Gsa (g alpha s) sub unit
What is the role of Gsa?
It dissociates from the b-gamma and goes to active adenyl cyclase which catalyses the conversion of ATP to cyclic AMP this inhibits release of calcium and encourages calcium sequestation prevents smooth muscule contraction
When does desensitisation occur?
When there is continual stimulation between the agonist and receptor
Why might we stop seeing an effect when using b2 agonists?
If we repeatedly stimulate with b2 agonists a tolerance can form so our body wont be seeing an effect reason why we use these in combination with other medicines
