Flecainide dosage

Serum flecainide levels are increased by amiodarone. The flecainide dosage should be reduced by between one-third and one-half. An isolated report describes a patient on amiodarone who developed torsade de pointes when given flecainide. 

Other authors have reported this interaction, and suggest reducing the flecainide dosage by between one-third to one-half when amiodarone is added. " Another study found that amiodarone raised steady-state flecainide plasma levels by 37% in extensive metabolisers, and 55% in poor me-tabolisers of dextromethorphan (a probe drug for CYP2D6 activity). In a later report of this study the authors concluded that these differences were nof clinically imporfanf, and that CYP2D6 phenotype does not affect the extent of the flecainide-amiodarone interaction. An isolated report describes torsade de pointes in a patient on amiodarone when given flecainide. ... 

An established interaction, but the documentation is limited. Reduce the flecainide dosage by one-fhird to one-half if amiodarone is added. The manufacturers of flecainide recommend a 50% reduction in dose if amiodarone is given, and advise that adverse effects and plasma flecainide levels should be monitored. There seems to be no need to treat extensive metabolisers differently from poor metabolisers. Remember that the interaction may take 2 weeks or more to develop fully, and also that amiodarone is cleared from the body exceptionally slowly so that this interaction may persist for some weeks after it has been withdrawn. 

An established but not extensively documented interaction. The clinical importance appears not to have been assessed, but be alert for the need to reduce the flecainide dosage if cimetidine is added. Caution is recommended in patients with impaired renal function, as the interaction is likely to be enhanced. ... 

Transfer to flecainide Theoretically, when transferring patients from another antiarrhythmic to flecainide, allow at least 2 to 4 plasma half-lives to elapse for the drug being discontinued before starting flecainide at the usual dosage. Consider hospitalization of patients in whom withdrawal of a previous antiarrhythmic is likely to produce life-threatening arrhythmias. 

Administration with amiodarone When flecainide is given in the presence of amiodarone, reduce the usual flecainide dose by 50% and monitor the patient closely for adverse effects. Plasma level monitoring is strongly recommended to guide dosage with such combination therapy. 

Hepatic function impairment Because flecainide elimination from plasma can be markedly slower in patients with significant hepatic impairment, do not use in such patients unless the potential benefits outweigh the risks. If used, make dosage increases very cautiously when plasma levels have plateaued (after more than 4 days). 

Side effects of flecainide therapy generally disappear with continued use or decreased dosage... 

Propafenone has some structural similarities to propranolol and possesses weak 3-blocking activity. Its spectrum of action is very similar to that of quinidine, but it does not prolong the action potential. Its sodium channel-blocking kinetics are similar to that of flecainide. Propafenone is metabolized in the liver, with an average half-life of 5-7 hours. The usual daily dosage of propafenone is 450-900 mg in three divided doses. The drug is used primarily for supraventricular arrhythmias. The most common adverse effects are a metallic taste and constipation arrhythmia exacerbation can also occur. 

Flecainide is very effective in suppressing premature ventricular contractions. However, it may cause severe exacerbation of arrhythmia even when normal doses are administered to patients with preexisting ventricular tachyarrhythmias and those with a previous myocardial infarction and ventricular ectopy (see The Cardiac Arrhythmia Suppression Trial). The drug is well absorbed and has a half-life of approximately 20 hours. Elimination is both by hepatic metabolism and by the kidney. The usual dosage of flecainide is 100-200 mg twice a day. 

In a review of 60 original articles detailing 1835 courses of intravenous and/or oral flecainide in both placebo-controlled and comparative studies as well as a large number of uncontrolled studies, unwanted cardiac events occurred in 8% of patients (7). The cardiac events were hypotension (1.3%), heart failure (0.4%), sinus node dysfunction (1.6%), bundle branch block (1.0%), atrial dysrhythmias (1.6%), and ventricular dysrhythmias (1.3%). However, in 8505 patients, 5507 of whom were administered flecainide for more than 4 weeks and most of whom took dosages of 100-300 mg/day, cardiac adverse effects occurred in only about 2% and non-cardiac effects in... 

At 30 weeks of gestation in a 41-year-old woman the fetus had hydrops, ascites, a pericardial effusion, and bilateral hydroceles. A supraventricular tachycardia with 1 1 conduction was treated by giving the mother oral flecainide 150 mg bd. However, during the next few weeks the mother developed evidence of hepatic cholestasis. The dosage of flecainide was reduced to 50 mg bd and the liver damage resolved. The child was born healthy but later required sotalol for a re-entry tachycardia. 

Flecainide is cleared partly by dose-dependent hydroxyla-tion and partly unchanged via the kidneys. Therefore, severe renal impairment and hepatic impairment both cause a reduction in its rate of clearance (57,58). Dosages should be reduced in these circumstances. 

Neff C A, Davis L E, Baggot J D 1972 A comparative study of the pharmacokinetics of quinidine. American Journal of Veterinary Research 33 1521-1525 Ohmura H, Nukada T, Mizuno Y et al 2000 Safe and efficacious dosage of flecainide acetate for treating equine atrial fibrillation. Journal of Veterinary Medical Science 62 711-715... 

Ohmura H, Hiraga A, Aida H et al 2001 Determination of oral dosage and pharmacokinetic analysis of flecainide in horses. Journal of Veterinary Medical Science 63 511-514... 

A premature baby being treated for refractory atrio-ventricular tachycardia with high doses of flecainide (40 mg/kg daily or 25 mg every 6 hours) developed flecainide toxicity (seen as ventricular tachycardia) when his milk feed was replaced by dextrose 5%. His serum flecainide levels ap-proximafely doubled, fhe conclusion being fhaf fhe milk had reduced the absorption. Milk-fed infants on high doses of flecainide may fherefore possibly need a reduced dosage if milk is reduced or stopped. Monitor the effects. 

A 69-year-old woman developed confusion and paranoia over several days. She was taking carvedilol 12 mg bd, warfarin 2 mg/day, folic add 1 mg/day, levothyroxine 100 micro-grams/day, pantoprazole 40 mg/day, paroxetine 40 mg/day, and flecainide 100 mg bd. The flecainide had been started 2 weeks before. The plasma flecainide concentration was 1.36 mg/1. Paroxetine was withdrawn and the dosage of flecainide was reduced to 50 mg bd. Her delirium resolved 3 days later. 

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