Marked sodium channel blockers

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Chapter: Medicinal Chemistry : Antiarrhythmic Drugs

Antiarrhythmic Drugs : Marked sodium channel blockers : i. Flecainide (Tambocar) ii. Encainide HCl iii. Lorcainide HCl iv. Propafenone HCl (Rhythmonorm) v. Aprindine HCl vi. Indecainide HCl vii. Pilsicainide HCl - Synthesis and Drug Profile, Structure, Properties, uses, Synthesis, Assay, Storage, Dosage forms, Dose


SYNTHESIS AND DRUG PROFILE


Marked sodium channel blockers


i. Flecainide (Tambocar)


Properties and uses: It is a white or almost white crystalline powder, very hygroscopic, soluble in water and in ethanol, insoluble in dilute hydrochloric acid and soluble in dilute acetic acid. Flecainide represents the first fluorine containing newer group of antiarrhythmic drugs. It is indicated for use in patients with life threatening arrhythmias, such as sustained ventricular tachycardia.

Assay: Dissolve the sample in anhydrous acetic acid. Titrate with 0.1 M perchloric acid and determine the end point potentiometrically.

Storage: It should be stored in well-closed airtight containers and protected from light.

Dose: The usual dose is orally, 100 mg twice daily with an average daily maintenance doses from 200 to 600 mg.

Dosage forms: Flecainide injection B.P., Flecainide tablets B.P.

Synthesis



ii. Encainide HCl


Uses: It is used in the treatment of cardiac dysfunction.


iii. Lorcainide HCl


Synthesis


Properties and uses: Lorcainide proved to be effective in reducing ventricular arrhythmias and tachycardias.

Dose: The usual dose is 100 mg, 2 or 3 times/day.


iv. Propafenone HCl (Rhythmonorm)


Properties and uses: It exists as white crystals, which is soluble in hot water and in alcohol. It is slightly soluble in cold water. It is a class I-c antiarrhythmic drug and contains a chiral centre, and is marketed as the racemic mixture. The racemic mixture of propafenone produces effects that can be attributed to both (S) and (R) enantiomers. The (R) and (S) enantiomers exert similar Na+ channel-blocking effects,

Synthesis


the (S) enantiomers also produces a β-adrenergic blockade. As a result, the (S) enantiomer is reported to be 40-fold more potent than the (R) enantiomers as an antiarrhythmic agent. The enantiomers also display stereoselective disposition characteristics. The (R) enantiomer is cleared more quickly. It is useful in supraventricular and ventricular tachycardias and tachyarrhythmias. It resembles the β adrenoceptor blockers of aryloxy propanol amines.

Assay: Dissolve the sample in anhydrous formic acid and add acetic anhydride. Titrate with 0.1 M perchloric acid, determine the end point potentiometrically.

Dose: Initially 150 mg thrice/day which can be gradually increased to twice the initial dose.


v. Aprindine HCl


Synthesis


Properties and uses: Aprindine is a powerful antiarrhythmic drug that may reverse both supraventricular and ventricular arrhythmias.


vi. Indecainide HCl


Properties and uses: It has shown itself to be a highly efficacious and well-treated antiarrhythmic drug for the suppression of ventricular tachycardias.

Synthesis



vii. Pilsicainide HCl


Properties and uses: Pilsicanide hydrochloride is a new pyrrolizidine lidocaine derivative with antiarrhythmic activity. It is effective in the treatment of premature ventricular contraction.


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