Antiarrhythmics intravenous

QuinidJne. Quinidine, an alkaloid obtained from cinchona bark (Sinchona sp.), is the dextrorotatory stereoisomer of quinine [130-95-0] (see Alkaloids). The first use of quinidine for the treatment of atrial fibrillation was reported in 1918 (12). The sulfate, gluconate, and polygalacturonate salts are used in clinical practice. The dmg is given mainly by the oral (po) route, rarely by the intravenous (iv) route of adniinistration. It is the most frequentiy prescribed po antiarrhythmic agent in the United States. The clinical uses of quinidine include suppression of atrial and ventricular extrasystoles and serious ventricular arrhythmias (1 3). 

Class IB drugs like lidocaine, phenytoin or mex-iletine preferentially bind to the inactivated state. Lidocaine, a local anaesthetic, can be used intravenously for antiarrhythmic treatment. It is one of the classical dtugs used in emergency medicine for the... 

Dantrolene is the mainstay of MH treatment. It has long been available for the treatment of muscle spasm in cerebral palsy and similar diseases. It is a hydantoin derivative that was first synthesized in 1967, and reported to be effective in the treatment of porcine MH in 1975. Also in 1975, dantrolene was shown to be more effective than procainamide in the treatment of human MH, which until that time was the drug of choice. However, the intravenous preparation was not made available until November 1979. It significantly lowered mortality. The half-life of dantrolene is estimated to be 6-8 hr. Dantrolene s primary mode of action is the reduction in calcium release by the sarcoplasmic reticulum. Dantrolene also exerts a primary antiarrhythmic effect by increasing atrial and ventricular refractory periods. Side effects of dentrolene include hepatotoxicity, muscle weakness, ataxia, blurred vision, slurred speech, nausea, and vomiting. Dantrolene is not contraindicated in pregnancy, but it does cross into breast milk and its effect on the neonate is unknown. 

A 36-year-old male is seen in the ED with tachycardia, a respiratory rate of 26 breaths per minute (BPM), and EKG evidence of an arrhythmia. An intravenous bolus dose of an antiarrhythmic agent is administered, and within 30 s, he has a respiratory rate of 43 BPM and complains of a burning sensation in his chest. 

Antiarrhythmic treatment with intravenously administered phenytoin as well as correction of the electrolyte balance (K+, Ca " ", Na+) should be performed. AV block may require a temporary pacemaker. Digitalis antibodies may be used as a specific antidote. 

Adenosine reduces heart rate and AV conduction, although it is not a calcium antagonist. It is administered intravenously for the acute treatment of paroxysmal supraventricular tachycardia. Adenosine displays a rapid onset and short duration of action. Apart from its antiarrhythmic activity it is also a vasodilator, in particular in the coronary system. 

Amide-type agents include articaine, lidocaine, bupivacaine, prilocaine, mepivacain and ropiva-caine. These are metabolized in the liver by microsomal enzymes with amidase activity. The amide group is preferred for parenteral and local use. If by accident rapidly administered intravascularly these agents, especially bupivacaine but also lidocaine, can produce serious and potentially lethal adverse effects including convulsions and cardiac arrest. They can more easily accumulate after multiple administrations. Intravenous lidocaine is sometimes used for regional anesthesia, for infiltration procedures, for the induction of nerve blockade and for epidural anesthesia. However, it is also used as an antiarrhythmic. Bupivacaine is a long-acting local anesthetic used for peripheral nerve blocks and epidural anesthesia. 

In the USA, amiodarone is approved for oral and intravenous use to treat serious ventricular arrhythmias. However, the drug is also highly effective for the treatment of supraventricular arrhythmias such as atrial fibrillation. As a result of its broad spectrum of antiarrhythmic action, it is very extensively used for a wide variety of arrhythmias. Amiodarone has unusual pharmacokinetics and important extracardiac adverse effects. Dronedarone, an analog that lacks iodine atoms, is under investigation. 

The cardiac arrhythmias are life-threatening, so the patient must be closely monitored, with facilities available for possible resuscitation. Drugs such as quinidine and procainamide are contraindicated, but lidocaine, propranolol, or phenytoin has been used safely and effectively. The arterial blood gas levels, pH, and electrolyte concentrations should be monitored so that metabolic acidosis or hypokalemia can be identified that would further aggravate the arrhythmias. Electrical pacing may be required if the antiarrhythmic drugs fail. Hyperpyrexia is treated by cooling. Seizures may be managed by intravenous doses of diazepam. 

Stambler BS, Wood MA, Ellenbogen KA. Antiarrhythmic actions of intravenous ibutilide compared with procainamide during human atrial flutter and fibrillation electrophysiological determinants of enhanced conversion efficacy. Circulation 1997 96( 12) 4298-4306. 

Correct answer = B. Lidocaine is useful in treating ventricular arrhythmias. Lidocaine is given intravenously because of extensive first-pass transformation by the liver, which precludes oral administration. All of the antiarrhythmic drugs can exert a negative inotropic effect. 

Some antiarrhythmics are rapidly degraded in the body by cleavage (see arrows in B) these substances are not suitable for oral administration but must be given intravenously (e.g lidocaine). 

SAFETY PROFILE Poison by ingestion and intravenous routes. An experimental teratogen. Human systemic effects by ingestion hallucinations and distorted perceptions. Experimental reproductive effects. An antiarrhythmic agent. When heated to decomposition it emits toxic fumes of NOx. 

BrembiUa-Perrot B, Terrier de la Chaise A. Provocation of supraventricular tachycardias by an intravenous class I antiarrhythmic drug. Int J Cardiol 1992 34(2) 189-98. 

Kowey PR, Marinchak RA, Rials SJ, Bharucha DB. Intravenous antiarrhythmic therapy in the acute control of in-hospital destabilizing ventricular tachycardia and fibrillation. Am J Cardiol 1999 84(9A) R46-51. 

Katoh T, Ishihara S, Tanaka T, Kobagasi Y, Takada K, Shimai S, Seino Y, Tanaka K, Takano T, Hayakawa H. Hemodynamic effects of intravenous cibenzoline, a new antiarrhythmic agent. Jpn J Chn Pharmacol Ther 1988 19 707-16. 

Sedgwick ML, Rasmussen HS, Cobbe SM. Clinical and electrophysiologic effects of intravenous dofetilide (UK-68,798), a new class III antiarrhythmic drug, in patients with angina pectoris. Am J Cardiol 1992 69(5) 513-17. 

Falk RH, Poliak A, Singh SN, Friedrich T. Intravenous dofetilide, a class III antiarrhythmic agent, for the termination of sustained atrial fibrillation or flutter. Intravenous Dofetilide Investigators. J Am CoU Cardiol 1997 29(2) 385-90. 

Alternative intravenous antiarrhythmics that may be used for SuVT include procainamide and amiodarone. For maintenance, oral antiarrhythmics such as sotalol, procainamide, amiodarone, and quinidine are possible options. 

Repeated doses of activated charcoal may enhance elimination. Serum electrolytes should be monitored in all serious exposures. Intravenous administration of sodium bicarbonate may decrease toxicity. Hypotension can be treated with fluids and vasopressors if needed. Ventricular dysrhythmias can be treated with class IB antiarrhythmics such as phenytoin or lido-caine. Persistent bradycardia and third-degree heart block are indications for insertion of a temporary pacemaker. Seizures can be treated with diazepam. If seizures are uncontrolled, phenobarbital or phenytoin can be administered. 

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