Amiodorone and k level

[ark-two]

What exactly happens when a patient is on amiodorone and they have a low potassium level? The reason I ask, a patient was on 400 mg of amiodorone (bolus dose), for conversion of a-fib. For me, the was sinus brady and asyptomatic. Hr 54-56. Bp fine, amiodorone q 6 hrs and atenolol ordered. I held both and wrote in progress noted I held and why. Did the low K level with the amiodorone cause the brady? And also the next am her k level was even lower with additional 40 meq po of k. Does amiodorone affect k level? My drug book does not go into detail about this. That night I did not have much time to look up at work.

[dianah, ASN]

I got this from http://www.anaesthetist.com/icu/drugs/manage/heart/amiodarone (I added the bold type) :

Interactions

Common interactions:

There is an erratic interaction with oral anticoagulants (warfarin) - if the two must be given together, perhaps halve the warfarin dose and watch the INR carefully;

Any drugs that cause bradycardia may be potentiated: beta blockers, calcium channel blockers; the metabolism of some beta blockers such as propranolol and metoprolol may be interfered with, potentiating their effects. Amiodarone + diltiazem may be particularly bad news.

Amiodarone increases digoxin levels (markedly reduce the digoxin dose and watch levels; or stop it)

Drugs that deplete the body of potassium (e.g. diuretics) should be avoided, or the potassium should be monitored and replaced Amiodarone may increase phenytoin levels

If amiodarone is combined with Vaughan Williams class I agents then proarrhythmic effects (even polymorphic ventricular tachycardia) may be potentiated. This has been seen with propafenone, disopyramide and mexiletine. Marked QT prolongation may indicate high risk! Quinine and procainamide levels may also be increased on amiodarone therapy. Try and avoid using amiodarone with any class I agent.

Rifampicin increases amiodarone levels [ Pharmacotherapy 1999 Feb;19(2):249-51 ]

Agents that cause hypotension (eg inhalational anaesthetics) may be potentiated - several studies suggest that patients on amiodarone are at increased risk of severe intra-operative complications, especially related to cardio-pulmonary bypass. Dysrhythmias and bradycardias were particularly evident e.g. complete heart block or pacemaker dependency up from 17% to 66%.

As it is an antiarrythmic, it doesn't deplete the body of K+. IF the pt is also taking diuretics, the K+ levels must be closely monitored. Abnormal K+ value will affect how well the cells will depolarize and repolarize, possibly interfering with the effects of the amiodarone (and possibly causing lethal arrythmias).

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