L17- Anti dysrhythmic drugs 2 Flashcards
Name 2 antagonists of B adrenoceptors
Propranolol, atenolol
Which Vaughan- Williams class are beta blockers in?
Class 2
class 2 = BETA 1 ADRENOCEPTORS.
What are the pro-arrhythmogenic actions of the SNS activity in the heart? (that beta blockers block)
- Increased discharge of SAN
- Increased automaticity in atrial myocardium
- Improved conduction through AVN
- Increased automaticity in ventricular myocardium
What do B-blockers do to heart rate?
- Slows down depolarisation, slower to reach threshold
- Slows sinus rythm
- Slows conduction through the AV node
What can arrhythmias be cause by?
- excessive catecholamine release
- increased tissue sensitivity to catecholamines
- myocardial infarction- tissue damage- stress- overactive sinus
Give 5 unwanted effects of beta adrenoceptor antagonists?
- Bronchoconstriction- BAD FOR ASTHMA
- Precipitation of cardiac failure/ heart block
- Hypoglaecaemia- BAD FOR DIABETICS- covers warning signs of hypoglaecemic shock, reduce insulin secretion in type 2.
- Cold extremities
- Vivid dreams- propranolol because lipid soluble
Which diseases should not be given beta blockers?
Asthma, diabetes, most for heart failure
What’s th structure of Ca and Na iion channels?
6 TM domains in each subunit. 4 subunits.
4th TMD controls voltage stuff.
Extracellular dip between 5th and 6th.
Where do most Na channel blockers act from?
Inside the cell
What happens to the Na channels when the membrane is depolarized?
The voltage-sensitive part moves and the channels open, letting more sodium in. Na floods in depolarizing cell even more, more positive.
Whats a nociceptor?
A bare nerve ending that sense pain
What are the two types of pain fibres?
A delta fibres- fast transmission, sharp pain
C fibres- slow transmission, dull burning pain
Which channels open and close at start and end of AP?
sodium open
sodium close
potassium open
potassium close
How do local anaesthetics work?
They block sodium channels. so Block APs. so block nociception.
What is the structure of local anaesthetics?
Aromatic group
Linker (whats broken down in body)
Amine group
How can you determine which linker is present in a local anaesthetic?
If it has an i in the prefix, indicates an amide linkage.
EG lidocaine. amide linkage
What’s the suffix for local anaesthetics?
caine.
eg procaine, cocaine, lidocaine
In which conditions do local anaesthetics work best?
Alkaline conditions
Why do local anaesthetics work when injected into the cell?
They are use-dependent blockers. so only bind to open form of the channel. Doesn;t like closed state. Likes hydrophobic pathway through channel.
In what class of VW drugs are local anaesthetics in?
Class 1 drugs. Blocks sodium channels.
What are the clinical uses of class 1 drugs?
Ventricular arrhythmias
What are the potential side effects of class 1 drugs?
Potential problems with the CNS, as it involves lots os sodium channels. Increases risk of death after an MI.
Which drugs are in class 1a, 1b, 1c?
a. disopyramide, procainamide - arrhythmias
b. lidocain - arrhythmias
c. flecainide- WPW syndrome and arrhythmias
Which drug can treat wolff parkinson white syndrome?
Felcainide (class 1c)
What are class IV drugs?
Calcium antagonists
Whats an example of a class IV drug to treat dysrrhythmias?
Verapamil
What do class IV drugs do in the heart?
Block L type VSCC
Slow SAN and AVN conduction
Suppress ectopic pacemakers
What are the adverse effects of calcium anatgonists?
Dangerous in ventricular dysrrhythmias
hypotension
oedema
(something about WPW syndrome??)
WHat are the subtypes of calcium channels?
L- heart
T-heart
N- neuronal
P- neuronal
Which L type calcium blocker can’t be used to treat dyrhythmias? (exam Q likely!)
Nifedipine
It can trat hypertension and angine. not dyrhythmias
It’s not use dependent so blocks everything!
