What Is Group I Antiarrhythmic Medicine?

Medical Video: Pharmacology - ANTIARRHYTHMIC DRUGS (MADE EASY)

Medications that prevent or treat arrhythmias are called antiarrhythmics. Antiarrhythmic drugs are classified according to the way they work in 5 groups, namely: group I includes drugs that reduce conduction and impact point-it is sodium channel, group II includes beta-blockers, group III drugs that extend the potential duration of action by slowing down efflux potassium, and group IV includes calcium-channel inhibitors.

The duration of the potential work method can be extended by inhibition efflux potassium, but also by extension influx sodium with slow sodium channels. Anomalies of these two mechanisms are the origin of the long-QT syndrome. According to the effects of repolarization associated with efflux potassium, group I antiarrhythmia is divided into 3 groups, Ia, Ib, Ic.

How do group I antiarrhythmic drugs work?

Class I antiaritmia inhibits influx sodium with voltage-gated channels, slowing the speed of phase 0 depolarization, which results in decreased conduction.

Class He. His class antiarrhythm, besides its effect on voltage-gated sodium channels, slowing down repolarization by inhibiting efflux. He class medicines include quinidine, hydroquinidine, disopyramide.

Quinidine. Quinidine is broad spectrum antiarrhythmics which is used on the basis of healing and prevention. Therapeutic use is treatment of supra-ventricular tachycardias. Use for the treatment of muscle cramps should be avoided because of the opposite effects that can occur.

Quinidine, an isomer of quinine, has a direct and indirect effect:

Direct action, related to action on voltage-dependent sodium channels: quinidine decreases the rate of conduction and slows diastolic depolarization. In addition, quinidine also prolongs the potential for action by inhibiting repolarization with potassium efflux, which extends the QT interval. This has a negative inotropic effect.
Indirect action: quinidine has an antimuscarinic effect and by inhibiting the effects of acetylcholine, quinidine tends to accelerate heart rate and facilitate atrioventricular conduction.

Hydroquinidine. Hydroquinidine has the same properties as quinidine.

Disopyramide. Disopyramide has properties similar to quinidine. Disopyramide also has an antimuscarinic effect.

Class Ib. Medicines in class Ib, besides their effects on sodium voltage-gated channels, also accelerates cell repolarization by increasing efflux potassium and decrease the duration of potential actions and periods refractory. Included in class Ib are lidocaine, phenytoin and mexiletine.

Lidocaine and mexiletine

Lidocaine and mexiletine, Mexitil, work on potential actions: slowing down, especially high doses, fast diastolic depolarization (phase 0) and shortening the duration of potential action by accelerating repolarization. Has a negative inotropic effect and the effects of vasodilator peripherals. Their actions are straightforward and of short duration.

Phenytoin. Phenytoin has the same properties as other Ib class products. Phenytoin is used in the form of a DILANTIN injection, but is slowly being replaced with phenytoin phosphate or fosphenytoine PRODILANTIN, which is hydrolyzed in the body as phenytoin.

Ic class. Ic class antiarrhythmi prevents voltage-dependent sodium channels and extend the polarization phase. The IC group includes flecainide, propafenone, and aprindine.

Flecainide. Flecainide, Tambocor *, reduces depolarization rate (phase 0), but does not modify the duration of the potential action because it has no effect on potassium channel.

Propafenone. Propafenone, Rythmol *, reduces the rate of depolarization (phase 0) and slow diastolic depolarization. Propafenone has activity beta-blocking which is low and only appears during an overdose.

Aprindine. Aprindine has an effect similar to flecainide and propafenone, but has adverse effects such as: leukopenia, agranulocytosis, cholestatic hepatitis reversible with interruptions in treatment.

Cibenzoline. Cibenzoline is usually incorporated into the antiarrhythmic Ic class, but has certain properties from class III and IV antiaritmias.

What are the side effects of group I antiarrhythmic drugs?

Side effects depend on the type of antiarrhythmic class I you use. class I antiarrhythmia has the same adverse effect, related to inhibition sodium channel. This effect is more or less marked according to the drug and the patient's condition, especially hydro-electrolytic equilibrium patient.

Class I antiaritmia can induce abnormal conditions at all levels: sinus, atrioventricular, and intra-ventricular.

Pro-arrhythmias or the arithmogenic effects of antiarrhythmics appear mainly in patients with abnormalities hydro-electrolytic, such as hypokalemia and hypomagnesemia.

Effect anticholinergic from class medicines he can produce tachycardia, dry mouth, urinary retention, blurred vision and constipation. Diarrhea, nausea, headache and dizziness are also common side effects of class I drugs. Quinidine increases digitalis toxicity, especially if there is hypokalemia. Quinidine, by delaying repolarization, can accelerate torsades de pointes (especially in patients with long-QT syndrome), ventricular tachyarrhythmia which occurs after depolarization. Disopryamide is contraindicated with patients with heart failure compensated by negative inotropic action; Propagenone can also suppress inotropy. IC compounds can increase the risk of sudden death in patients with a history of continuous myocardial infarction or ventricular arrhythmias.

What should be considered?

Always consult a doctor before using group I antiarrhytmic. Tell your doctor if you are or plan to become pregnant or are breastfeeding. Also tell the doctor what medications you use, including natural and herbal supplements. Tell your doctor if you have an allergy to group I antiarrhythmic treatment.

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What Is Group I Antiarrhythmic Medicine?

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