Antiarrythmics Flashcards
where do the Class I antiarrythmic drugs act upon?
what are their names
what is the exact action of each group
Class I: Na+ channel blockers
- class I is further sub-divided into class Ia, Ib & Ic drugs depending on their potency: how WELL they are able to block sodium channels (class C being the most potent)
Class Ia (A = Double Quarter Pounder)
- Disopyramide
- Quinidine
- Procainamide
action of Class Ia
- slow condution velocity
- prolong refractoriness (risk of torsades) (class A = after — the repolarization takes longer, AFTER the normal)
- decrease automaticity
Class Ib ( B = Lettuce, Mayo)
- lidocaine
- mexiletine
Action of Class Ib
- minimal effect on condution velocity
- shorter refractory (less QT prolongation) (B = before the normal repolarization)
- decrease automaticity
Class Ic (most potent at stopping Na+ channels) (C = Fries, Please)
- Flecainide
- Propafenone
Action of Class Ic
- most potent Na channel blocker
- extremely slow conduction velocity
- do NOT affect refractoriness (no QT prolongation) becuase C = correct!!
- decrease automaticity
Where do Class II anti-arrythmic drugs work?
names?
electrical actions?
Class II: Beta Blocks
all the beta blockers (-olol)
Electrical Actions
- slow conduction
- act on the SA and AV node
- prolong refractory
- decrease automaticity
Where do the Class III anti-arrythmics work?
names
electrical actions?
Class III: work on the K+ channels to block them: most commonly used anti-arrythmics
Names ( ADDS)
- amiodarone
- dofetilide
- dronedarone
- sotalol
Electrical Action
- no effect on the velocity or automaticity of the cells
- significantly prolongs the QT during refractory
Where do the Class IV anti-arrythmics work?
names
electrical actions
Class IV: Calcium channel blockers
- block calcium channels
Names
- non-dihydropyradines (verapimil & diltiazem)
action
- work to slow rate!!
- act on SA and AV node
- slow conduction velcotiy
- prolong refractoriness
- decrease automaticity
indications for the use of Class Ib anti-arrythmics
adverse effects of Class Ib
Class Ib: sodium channel blockers; specifically lidocaine & mexiletine
- B = better: shorter QT
Lidocaine
- only used in ventricualr arrythmias
- V tach, Vfib
Mexiletine
- Vtach ONLY
Adverse Effects: Lidocine
- paresthesias
- slurred speech
- altered consciousness
- muscle twitch
- seizures
- only use up to 3 days max. & watch neuro symptoms
Thearpeudic range: 1.5-5mg/L
- monitor levels if infusion is > 24 hours (as it can accumulate)
indication for Class Ic drugs to be used
Class Ic: sodium channel blockers; which do not effect the QT interval
(C = continued use)
these are used once the pt. is STABLE and recovered from the afib/aflutter ot vtach – these are NOT meds used to get them out of the arrythmia
Flecainide
- for afib or aflutter or for Vtach
- Flec: “flekey hearts” aka those without structural heart disease
- cannot be sued in those with structural heart disease
Propafenone
- afib/aflutter or for vtach
- has additive b-blocker properties but non-specific for which beta (aka slows conduction through the AV node)
- in Afib specifically: “pro” hearts = aka those without structural heart disease
- cannot be used for those with structural heart disease– increased mortality
what is structrual heart disease
- left ventricular dysfunction (systolic or diastolic)
- cornary artery disease
- valvular disease
- left ventricualr hypertrophy (like chronicn HTN)
Adverse Reactions of the Class Ic anti-arrythmics
Flecainide Side Effects
- dizzy, HA
- tremor, blurry vision
- QRS interval prolongation because its slowing conductivity!!)
- worsen Herat failure (becuase its an negative inotrope: decreases the hearts ability to work)
- Proarrythmias!!! (doesnt CAUSE QT interval prolongation, so torsades not a side effect, but others can occur)
Propafenone Side Effects – because of the slow conduction
- bradycardia
- heart block
- HA, dizzy
- blurred vision
- taste disturbances
- worsening HF (because negative inotrope)
- nausea
- bronchospasm (acts on B2 a little – beta- blocker effect)
- QRS interval prolongation
- Proarrythmias!! (wont cause QT prolongation or torsades, but others)
Indications for use of the Class III anti-arrythmics
Class III: ADDS aka Amioderone, dofetilide, dronedarone, sotalol –> potassium channel blockers
remember MOA: potssium channel blocker aka prolongs the QT interval, no affect on automaticity or velocity of conduction
Indications: (All can be used for afib!)
Amiodarone
- Afib/Aflutter
- Vtach/Vfib
Dofetilide
- Afib/Aflutter
Dronedarone
- afib
Sotalol
- Afib/Aflutter
- Vtach
Amiodarone
- pharmacology (main action)
- indications for use
Main action = potassium channel blocker
(has other additive properties of sodium channel, beta blokcers and CCBs as well)
Indications
- a fib/aflutter, vtach/vfib
- safe to use in heart failure pts!! (can be used in structural heart disease)
- low incidence of proarrythmias
- no association with increased mortality
- in-patient or out-patient med
Amiodaone Side Effects
- Thyroid
- Lungs
- Liver
- GI
- Eyes
- Derm
- cardiac
- neurologic
amiodarone has a large Vd thus it gets everywhere (it also has a long half life of 60 days– stays arond for a long time)
Thyroid a big SE because amiodarone contains iodine
- hypothyroidism (more common)
- hyperthyroidism
- treatment = treat the thyroid disorder
Lungs
- pulmonary fibrosis – D/C drug IMMEDIATELY
- PF: cough, sob, fever, infiltrates on cxr –> corticosteroid
Liver
- increase LFTs (3-4x) monitor LFTS routinely
- if elevated –> decrease dose
GI
- N/V
- anorexia
- constipation
- often seen with higehr dose –> decrease dose to decrease
Eyes
- corneal microdeposits (doesnt change the vision so they’re okay)
- optic neuritis this DOES impact vision D/C drug immediately
Dermatologic
- photosensitive (wear sunscreen)
- blue-grey discoloration!!! (sunscreen!!!)
Cardiac
- bradycardia
- heart block
- decrease dose or pacemaker
Neurogenic
- tremor
- ataxia
- insomnia
- peripheral neuropathy
- manage via decreasing dose
Drug Interactions with Amiodarone
- what CYP
- what drugs
Amiodarone: is a CYP3A4 substrate and inhibitor
Phenytoin : will decrease amiodarone concentrations (inducer)
CYP3A4 inhibitor: will increase amiodarone concentratiosn (increase side effects)
Warfarin: Amiodarone will increase warfarin (becasue its an inhibitor at the substrate) leading to high warfarin doses combat this via decreasing warfarin dose by 30%
Statins: increase the statin concentration & increase myopathy side effects
max dose of lovastatin = 40 & simvistatin = 20
P-gylcoprotein inhibitor = digoxin!
- it will increase levesl of digoxin –> combat by decreasing the dogoxin level by 50%
Amiodarone Monitoring Guidelines
initally get a baseline for…
- chest xray
- PFT
- thyroid
- optho. exam
- LFTs
- EKG
If symptoms develop then get the appropriate…
- high-res CT (for pulm)
- PFT (for pulm fiberosis suspect)
- optho. (for eyes)
get every 6 months after baseline…
- thyroid function (TFT)
- LFTs (liver)
- EKG (3-6 months)
get annually…
- chest xray
Dofetilide
- indications for use
- monitoring
- FDA requirements
dofetilifde: Class III antiarrythmic (acts on the potassium channels)
Indications for use
- afib/aflutter
- can be used in those with structural heart disease
Monitoring
- drug interactions
- torsades de pointes risk!!: contraindicated if teh QT interval > 440 msec.
- renal function: dose adjustment for renal impairement
- contraindicated for CrCL < 20
FDA requirement
- due to the risk of developing torsades –> pts. must be hospitalized for > 3 days when started on this med & cannot be d/c within 12 hours of sync. cardioversion back to sinus
- in hosptial: monitor EKG conitinuously, watch renal impairment & resusicate if TDP occurs
Drug interactions with Dofetilide
all of these will INCREASE the level of dofetilide
- verapimil
- HCTZ
- timethorpim
- ketoconazole
- cimetidine (acid block OTC!)
- procholorperazine (nausea med)
- megestrol
- doultegravir
- QT-interval prolonging meds (quinolones, macrolides)
