Prajmaline

Mechanism

Prajmaline causes a resting block in the heart. A resting block is the depression of a person's Vmax after a resting period. This effect is seen more in the atrium than the ventricle. The effects of some Class I antiarrhythmics are only seen in a patient who has a normal heart rate (~1 Hz). This is due to the effect of a phenomenon called reverse use dependence. The higher the heart rate, the less effect Prajmaline will have.

Uses

The drug Prajmaline has been used to treat a number of cardiac disorders. These include: coronary artery disease, angina, paroxysmal tachycardia and Wolff–Parkinson–White syndrome. Prajmaline has been indicated in the treatment of certain disorders where other antiarrhythmic drugs were not effective.

Administration

Prajmaline can be administered orally, parenterally or intravenously. Three days after the last dose, a limited effect has been observed. Therefore, it has been suggested that treatment of arrhythmias with Prajmaline must be continuous to see acceptable results.

Pharmacokinetics

The main metabolites of Prajmaline are: 21-carboxyprajmaline and hydroxyprajmaline. Twenty percent of the drug is excreted in the urine unchanged.

Daily therapeutic dose is 40–80 mg. Distribution half-life is 10 minutes. Plasma protein binding is 60%. Oral bioavailability is 80%. Elimination half-life is 6 hours. Volume of distribution is 4-5 L/kg.

Side Effects

There are no significant adverse side-effects of Prajmaline when taken alone and with a proper dosage. Patients who are taking other treatments for their symptoms (e.g. beta blockers and nifedipine) have developed minor transient conduction defects when given Prajmaline.

Overdose

An overdose of Prajmaline is possible. The range of symptoms seen during a Prajmaline overdose include: no symptoms, nausea/vomiting, bradycardia, tachycardia, hypotension, and death.

Other Potential Uses

Due to Prajmaline's sodium channel-blocking properties, it has been shown to protect rat white matter from anoxia (82 +/- 15%). The concentration used causes little suppression of the preanoxic response.

References

References

1. (1995). "[Antiarrhythmic effects of prajmaline (Neo-Gilurythmal) in stable angina pectoris in light of Holter electrocardiographic monitoring]". Przegląd Lekarski.
2. (June 1990). "Differential analysis of the frequency-dependent effects of class 1 antiarrhythmic drugs according to periodical ligand binding: implications for antiarrhythmic and proarrhythmic efficacy". Journal of Cardiovascular Pharmacology.
3. (1990). "Clinical course and outcome in class IC antiarrhythmic overdose". Clinical Toxicology.
4. (February 1984). "Class 1 antiarrhythmic drugs--characteristic electrocardiographic differences when assessed by atrial and ventricular pacing". European Heart Journal.
5. (July 2000). "The structure of the ring-opened N beta-propyl-ajmaline (Neo-Gilurytmal) at physiological pH is obviously responsible for its better absorption and bioavailability when compared with ajmaline (Gilurytmal)". Die Pharmazie.
6. (February 1990). "Comparative analysis of the action of class I antiarrhythmic drugs (lidocaine, quinidine, and prajmaline) in rabbit atrial and ventricular myocardium". Journal of Cardiovascular Pharmacology.
7. (November 1992). "Reverse use dependence of antiarrhythmic class Ia, Ib, and Ic: effects of drugs on the action potential duration?". Pacing and Clinical Electrophysiology.
8. (1984). "Acute haemodynamic effects of ajmaline and prajmaline in patients with coronary heart disease". European Journal of Clinical Pharmacology.
9. (1985). "Effects of oral prajmaline bitartrate on exercise test responses in patients with coronary artery disease". European Journal of Clinical Pharmacology.
10. Stys PK. (May 1995). "Protective effects of antiarrhythmic agents against anoxic injury in CNS white matter". Journal of Cerebral Blood Flow and Metabolism.
11. (March 2005). "Differential effects of Na-K-ATPase pump inhibition, chemical anoxia, and glycolytic blockade on membrane potential of rat optic nerve". Brain Research.