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9780521704632c14 CUFX213A/Peck 9780521618168 December 28, 2007 12:32
Section IIICardiovascular drugsOphthalmic examination is recommended annually for those on long-term treat-
ment.
Gut–during the loading dose a metallic taste may be noticed. Minor intestinal
upset is seen occasionally.
Neurological – peripheral neuropathy and rarely myopathy have been repor-
ted.
Dermatological – the skin becomes photosensitive and may remain so for a number
of months after finishing treatment. A slate-grey colour particularly of the face may
develop.
Interactions – the effects of other highly protein bound drugs (phenytoin, war-
farin) are increased and their doses should be adjusted. The plasma level of
digoxin may rise when amiodarone is added due to displacement from plasma
protein-binding sites and cause signs of toxicity. Caution should be exercised
when used with drugs that slow AV conduction (β-blockers, verapamil) and
it should not be given with other drugs that prolong the QT interval (phenoth-
iazines, TCAs, thiazides) for fear of precipitating torsades de pointes.
Miscellaneous – the intravenous preparation is irritant and should be administered
via a central vein.Kinetics
Amiodarone is poorly absorbed from the gut and has an oral bioavailability between
50% and 70%. In the plasma it is highly protein bound (>95%) and has a vol-
ume of distribution of 2–70 l.kg−^1 .Muscle and fat accumulate amiodarone to a
considerable extent. Its elimination half-life is long, varying from 20 to 100 days.
Hepatic metabolism produces desmethylamiodarone, which appears to have some
anti-arrhythmic activity. It is excreted by the lachrymal glands, the skin and biliary
tract.Flecainide
Presentation
Flecainide is available orally or intravenously and is an amide local anaesthetic with
class Ic properties. The oral dose is 100 mg bd (maximum 400 mg daily). When
used intravenously the dose is 2 mg.kg−^1 over 10–30 minutes (maximum 150 mg).
This may then be followed by an infusion, initially at 1.5 mg.kg−^1 .h−^1 ,which is
then reduced to 100–250μg.kg−^1 .h−^1 for up to 24 hours (maximum 24-hour dose is
600 mg).Uses
Flecainide has powerful anti-arrhythmic effects against atrial and ventricular tach-
yarrhythmias including WPW syndrome.