Pharmacological properties : תכונות פרמקולוגיות

Pharmacodynamic Properties

5.1 Pharmacodynamic properties
Pharmacotherapeutic group: Cardiac therapy. Antiarrhythmic Class Ic.
ATC code: C01BC04.

Tambocor tablets is a class 1c antiarrhythmic agent with negative inotropic activity. It binds to the sodium channels of muscle membranes, producing a potent slowing of cardiac impulse conduction and a suppression of spontaneous premature ventricular complexes.
Within the heart Tambocor tablets binds strongly to fast sodium channels and so slows the rate of depolarisation and conduction in the atria, atrio-ventricular node, ventricular and Purkinje fibres is decreased. The most profound effect is observed upon the Purkinje fibres.
Its actions may be reflected in the ECG by prolongation of the PR interval and widening of the QRS complex. The effect on the JT interval is insignificant.

Pharmacokinetic Properties

5.2 Pharmacokinetic properties

Following oral administration, the absorption of Tambocor tablets is almost complete (90%), and peak plasma concentration occurs after 3-4 hours. It is weakly plasma bound (40%). In patients, 200 to 600 mg Tambocor tablets daily produced plasma concentrations within the therapeutic range of 200-1000 μg/L. Protein binding of
Tambocor tablets is within the range 32 to 58%. Oral absorption does not appear to be affected by either food or antacids.

In healthy subjects the plasma half-life of Tambocor tablets is 12-13 hours after a single oral dose. However, the plasma half-life is prolonged after multiple oral doses (16 hours) and in patients with ventricular arrhythmia's (20 hours).

After oral absorption Tambocor tablets is metabolised by the liver and undergoes extensive biotransformation. Approximately 86% of a dose is excreted in the urine, 27% as unchanged flecainide acetate and 59% as metabolites. The two major urinary metabolites are meta-O- dealkylated flecainide acetate and meta-O-dealkylated lactam of flecainide acetate. (Only 5% of an oral dose is excreted in the faeces). These metabolites have no clinically significant antiarrhythmic effects.

The rate of Tambocor tablets elimination from plasma is reduced in the presence of renal failure, liver disease and congestive heart failure. The urinary excretion of Tambocor tablets is reduced in patients with renal failure and significantly so in patients with severe renal failure.