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Flashcards in CVS Deck (45)
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Digoxin: Mechanism of Action

It is negatively chronotropic as it slows conduction at the AV node by increasing vagal tone.
It is positively intotropic as it inhibits Na+/K+ pumps. This causes an increase in intracellular sodium, and therefore reduces Ca2+ excretion so Ca2+ accumulates in the myocytes and their contractility is increased.


Digoxin: Indications

AF and atrial flutter, though a B blocker or CCB is usually more effective
In severe heart failure, as 3rd line treatment after B blocker and ACEI and spironolactone/ARB


Digoxin: Adverse Effects

Bradycardia, GI upset, rash, dizziness, visual disturbance.
It is pro-arrhythmic


Digoxin: Warnings and Interactions

Low therapeutic index. OD can cause weird and wonderful arythmias.
It is contraindicated in those at risk of ventricular arrhythmia or heart block
It is really excreted so dose should be reduced in renal impairment
Hypokalaemia and hypercalcaemia increase the risk of digoxin toxicity

Interacts with loop/thiazide diuretics as they can cause hypokalaemia


Digoxin: Prescription

Oral or IV
Large volume of distribution so loading dose is required
Cardiac monitoring!


Diuretics, Loop (Furosemide): Mechanism of Action

Inhibit Na/K/2Cl transporter in ascending limb. Also causes dilation of capacitance veins.


Diuretics, Loop (Furosemide): Indication

Acute pulmonary oedema
Chronic heart failure
Other oedematous states


Diuretics, Loop (Furosemide): Adverse effects

Dehydration, hypovolemia, loss of electrolytes
Hearing loss at high doses


Diuretics, Loop (Furosemide): Warnings and Interactions

Contraindicated in dehydration or hypotension, and hypokalaemia
Can worsen gout as they inhibit uric acid excretion

Increase levels of renal excreted drugs
Increase ototoxicity of ahminoglycosides
Cause digoxin toxicity by hypokalaemia


Diuretics, Loop (Furosemide): Prescription

Oral and IV
Periodic monitoring of electrolytes for safety


CCBs (Amlodipine): Indications

Non-dihydropyridine drugs (verapamil) are anti-arrhythmic and can be used to treat SVT, AF and flutter


CCBs (Amlodipine): Mechanism of Action

Decrease Ca2+ entry, so decrease smooth muscle contractility. They also slow conduction, especially across the AV node.


CCBs (Amlodipine): Adverse Effects

Ankle swelling, flushing, headache and palpitations
Verapamil can cause bradycardia


CCBs (Amlodipine): Warnings and Interactions

Verapamil SHOULD NOT be prescribed alongside a B blocker as this can cause dangerous bradycardia or even ayststole
Should be avoided in unstable angina as they can increase myocardial oxygen demand


CCBs (Amlodipine): Prescription

Taken orally (except verapamil can be given IV for acute arrhythmia)
Amlodipine has a long half life so can be given once daily
Monitering is based on symptoms and BP measurements


Lidocaine: Indications

Local anaesthetic
Uncommonly as anti arrhythmic for VT and VF that cannot be cardioverted


Lidocaine: Mechanism of Action

Na+ channel blocker, so prevents initiation and propagation of action potentials
In the heart it reduces the duration of the action potential, slows conduction and increases the refractory period


Lidocaine: Adverse Effects

Drowsiness, tremor, fits
Effects more pronounced when used systemically
OD can cause hypotension and arrhythmia


Lidocaine: Warnings and Interactions

Dose reduction in patients with reduced CO
Beneficial interaction with adrenaline (local vasoconstrictor)


Lidocaine: Prescription

Maximum dose is based on body weight
(Foundation doctors should not prescribe it systemically)


Amiodarone: Indictions

A wide range of tachyarrhythmias e.g. AF, SVT, VT, VF...
Generally when other treatments have been ineffective


Amiodarone: Mechanism of Action

It is a Class III drug so blocks K+ channels (It actually also blocks Ca2+, Na+ and antagonises adrenoreceptors)
This reduces spontaneous depolarisation, decreases conduction velocity and increases resistance to depolarisation


Amiodarone: Adverse Effects

When taken chronically: pneumonitis, hepatitis, bradycardia


Amiodarone: Warnings and Interactions

Actually quite a dangerous drug, so consider risks and benefits
Avoid in thyroid disease, hypotension or heart block
It interacts with lots and lots of drugs; especially digoxin and verapamil


Amiodarone: Prescription

Requires senior input
Continous cardiac monitoring


Beta Adrenoceptor Blockers: Indications

Ischaemic Heart Disease
Chronic Heart Failure
Atrial Fibrillation
HTN, when ACEIs and CCBs have not worked


Beta Adrenoceptor Blockers: Mechanism of Action

Then antagonise B1 receptors. They are negatively chronotropic and inotropic
They also increase the refractory period at the AV node
They reduce renin secretion


Beta Adrenoceptor Blockers: Adverse Effects

Hypotension, cold peripheries, GI upset, fatigue, headache


Beta Adrenoceptor Blockers: Warnings and Interactions

Should be avoided in asthmatics (bronchospasm)
In heart failure, start at a low dose and slowly increase as they can initially impair cardiac function
AVOID with VERAPAMIL as this is bad (bradycardia, asystole)


Beta Adrenoceptor Blockers: Prescription

Monitoring is based on symptoms and heart rate
Timing doesn't matter