Session 9 Flashcards
(16 cards)
What are the two main mechanisms of action of antiarrhythmic drugs?
Reduce abnormal impulse generation - decrease slope in pacemaker cells, raise threshold
Slow conduction through tisssue - reduce conduction velocity, increase effective refractory period
Give the mechanism of action, examples, uses and side effects of class 1A anti arrhythmic agents
Sodium channel blockers affecting phase 0 of the cardiac action potential. Quinidine - maintain sinus rhythm in AF/flutter.
Side effects - hypotension, long QT (proarrhythmic), GI upset, confustion, seizures
Give the mechanism of action, examples, uses and side effects of class 1B anti arrhythmic agents
Sodium channel blockers that increase the threshold and decrease phase 0 conduction in fast beating ischaemic tissue. Lidocaine (IV only) - VT
Side effects - dizziness, GI upset, bradycardia
Give the mechanism of action, examples, uses and side effects of class 1C anti arrhythmic agents
Sodium channel blockers, substantially decrease phase 0, increase threshold and increase refractory period. Flecainide - AF/flutter, WPW syndrome
Side effects - proarrhythmic especially in chronic use and those who have a structural heart defect, CNS and GI effects
Give the mechanism of action, examples, uses and side effects of class II anti arrhythmic agents
Beta blockers - slows AV conduction (increases AP duration and refractory period), decreases phase 4 depolarisation. Propranolol/bisoprolol - sinus and catecholamine dependent tachycardia, slows AV conduction in AF/flutter
Side effects - bronchospasm, hypotension
Give the mechanism of action, examples, uses and side effects of class III anti arrhythmic agents
Potassium channel blockers - increase AP duration, refractory period and threshold, slow AV conduction.
Amiodarone - most arrhythmias and VF/VT. Side effects include pulmonary fibrosis, hepatic injury, thyroid disease, photosensitivity, transient blindness
Sotalol - also beta blocker action. Uses for SVT and VT. Side effects include proarrhythmic, fatigue, insomnia
Give the mechanism of action, examples, uses and side effects of class IV anti arrhythmic agents
Calcium channel blockers, slow AV conduction, increase refractory period and slows HR.
Verapamil - SVT. Side effects - GI problems, hypotension, asystole if AV block
Give the mechanism of action, uses and side effects of adenosine
Nucleoside that binds to A1 receptors activating potassium channels in AV and SA nodes. The hyperpolarisation reduces AV node conduction.
Converts SVT
Side effects - angina, dizziness, AV block, hypotension
Give the mechanism of action, uses and side effects of digoxin
Cardiac glycoside - inhibits Na/K ATPase. Increases contractility and slows AV node conduction. Used in maintenance of AF/flutter
Side effects - arrhythmias, yellow vision, dizziness, GI upset, narrow therapeutic range
Outline the pain pathway
Nociceptor -> Type A (myelinated) and type B (non myelinated) -> dorsal root of spinal cord (substantia gelantinosa) -> Thalamus and primary sensory cortex
Neurotransmitters; substance P and glutamate
What are the 3 major groups of endogenous opioids?
Enkephalins, endorphins, dynorphins
What are the 3 major types of opioid receptor?
Mu (MOP - where most exogenous opioids act), delta (DOP), kappa (KOP)
All GPCR
Name an agonist, partial agonist/antagonist and an antagonist of opioid receptors
Agonist - morphine (Mu)
Agonist/antagonist - nalbuphine. Partial agonist of delta and kappa, antagonist of Mu. Allows analgesia without euphoria
Antagonist - naloxone
Compare the pharmacokinetics of morphine with methadone
Methadone has a longer half life (1 day compared to 4-5 hours) and a higher oral bioavailability (90% compared to 25%)
Why doesn’t codeine achieve analgesia in 10% of the caucasian population?
It is converted to morphine in the liver to become active by a specific enzyme hat can be absent
(DIamorphine has half life of 5 minutes)
List some of the side effects of opioids
Respiratory depression, euphoria, confusion, miosis,
psychosis, coma, nausea and constipation.
