Pre Reg MONITORING INTERACTIONS COUNSELLING1 1 
THE ULTIMATE PRE REG BNF NOTES
IMPORTANT MONITORING DRUGS
1. AMIODARONE
Treatment of arrhythmias
Loading Dose: 200mg tds for 7 days, then 200mg bd for 7 days then 200mg daily maintenance.
Important side effects: Nausea, Vomiting, Taste disturbance, Pulmonary toxicity, Reversible corneal micro-deposits, Phototoxicity, Slate grey discolouration, Tremor, Sleep disorder, Hypo/hyperthyroidism, Jaundice.
Monitoring: LFTs, Thyroid function tests required before treatment, then every 6 months. Measure serum potassium concentration before treatment. Chest x-ray required before treatment. ECG monitoring and resuscitation facilities must be available during intravenous use.
A very long half life – there is potential for drug interactions to occur for several weeks (or even months) after treatment has stopped.
The Drugs
The Interaction
Amiodarone and Warfarin
Amiodarone inhibits Warfarin metabolism – enhanced anticoagulant effect
Amiodarone and β Blockers
Increased risk of bradycardia, AV block and myocardial depression
Amiodarone and Lithium
Risk of ventricular arrhythmias
Amiodarone and Digoxin
Plasma conc. of Digoxin increased by Amiodarone
2. DIGOXIN
A cardiac glycoside – used in AF, tachycardias and heart failure.
A positive inotrope – increases the force of myocardial contraction and reduces conductivity within the AV node.
Desired serum concentration: 1-2mcg/L (1.5mcg-3mcg/L indicates toxicity)
Monitoring: Serum electrolytes (especially potassium) and Renal function.
A narrow therapeutic index, Possibility of Digitalis toxicity, made worse by hypokalaemia. Managed by giving potassium sparing diuretic or potassium supplements. Note: Elderly more susceptible to digitalis toxicity.
Important side effects: Nausea, Vomiting, Diarrhoea, Dizziness, Blurred vision.
The Drugs
The Interaction
Digoxin and Amiodarone
Plasma conc. of Digoxin increased by Amiodarone
Digoxin and Erythromycin
Plasma conc. of Digoxin increased by Erythromycin
IMPORTANT MONITORING DRUGS
1. AMIODARONE
Treatment of arrhythmias
Loading Dose: 200mg tds for 7 days, then 200mg bd for 7 days then 200mg daily maintenance.
Important side effects: Nausea, Vomiting, Taste disturbance, Pulmonary toxicity, Reversible corneal micro-deposits, Phototoxicity, Slate grey discolouration, Tremor, Sleep disorder, Hypo/hyperthyroidism, Jaundice.
Monitoring: LFTs, Thyroid function tests required before treatment, then every 6 months. Measure serum potassium concentration before treatment. Chest x-ray required before treatment. ECG monitoring and resuscitation facilities must be available during intravenous use.
A very long half life – there is potential for drug interactions to occur for several weeks (or even months) after treatment has stopped.
The Drugs
The Interaction
Amiodarone and Warfarin
Amiodarone inhibits Warfarin metabolism – enhanced anticoagulant effect
Amiodarone and β Blockers
Increased risk of bradycardia, AV block and myocardial depression
Amiodarone and Lithium
Risk of ventricular arrhythmias
Amiodarone and Digoxin
Plasma conc. of Digoxin increased by Amiodarone
2. DIGOXIN
A cardiac glycoside – used in AF, tachycardias and heart failure.
A positive inotrope – increases the force of myocardial contraction and reduces conductivity within the AV node.
Desired serum concentration: 1-2mcg/L (1.5mcg-3mcg/L indicates toxicity)
Monitoring: Serum electrolytes (especially potassium) and Renal function.
A narrow therapeutic index, Possibility of Digitalis toxicity, made worse by hypokalaemia. Managed by giving potassium sparing diuretic or potassium supplements. Note: Elderly more susceptible to digitalis toxicity.
Important side effects: Nausea, Vomiting, Diarrhoea, Dizziness, Blurred vision.
The Drugs
The Interaction
Digoxin and Amiodarone
Plasma conc. of Digoxin increased by Amiodarone
Digoxin and Erythromycin
Plasma conc. of Digoxin increased by Erythromycin