Quinidine side effects

Disopyramide, proprietary name Norpace, is used for maintenance of sinus rhythm in patients with atrial flutter and atrial fibrillation and for prevention of ventricular tachycardia and fibrillation. The mechanism of action of disopyramide is similar to that of quinidine, and the drug can be used as replacement therapy for quinidine when quinidine side effects are intolerable. 

Although quinine is a favored antimalarial for parenteral adrninistration, it is nevertheless hazardous by this route. Quinidine (64), has been shown to be even more effective in combatting the disease (Table 8). However, it has undesirable cardiac side effects that reduce its suitabiHty as an antimalarial. 

Further class IA drugs include the open state blockers procainamide and disopyramide with electrophysiolog-ical effects similar to those of quinidine procainamide lacks the antimuscarinic and antiadrenergic effects. Characteristic side effects of procainamide are hypotension and immunological disorders. 

The cardiac toxicity of quinidine includes A-V and intraventricular block, ventricular tachyarrhythmias, and depression of myocardial contractility. Ventricular arrhythmia induced by quinidine leading to a loss of consciousness has been referred to as quinidine syncope. This devastating side effect is more common in women than in men and may occur at therapeutic or subtherapeutic plasma concentrations. 

Nelfinavir (Viracept) is probably the most commonly used protease inhibitor because of its low incidence of serious adverse effects. Its most common side effects are diarrhea and flatulence these may resolve with continued use. In addition to the drugs contraindicated for use with all protease inhibitors, amiodarone, rifampin, and quinidine are contraindicated in patients taking nelfinavir. 

Artemisinins are also proving to have outstanding efficacy for the treatment of complicated falciparum malaria. Large randomized trials and meta-analyses have shown that intramuscular artemether has an efficacy equivalent to that of quinine and that intravenous artesunate is superior to intravenous quinine in terms of parasite clearance time and—most important—patient survival. Intravenous artesunate also has a superior side-effect profile compared with that of intravenous quinine or quinidine. Thus, intravenous artesunate will likely replace quinine as the standard of care for the treatment of severe falciparum malaria, although it is not yet widely available in most areas. Artesunate and artemether have also been effective in the treatment of severe malaria when administered rectally, offering a valuable treatment modality when parenteral therapy is not available. 

Quinidine is used for the maintenance of normal sinus rhythm in patients with atrial flutter or fibrillation. It is also used occasionally to treat patients with ventricular tachycardia. Because of its cardiac and extracardiac side effects, its use has decreased considerably in recent years and is now largely restricted to patients with normal (but arrhythmic) hearts. In randomized, controlled clinical trials, quinidine-treated patients are twice as likely to remain in normal sinus rhythm compared with controls. However, drug treatment was associated with a twofold to threefold increase in mortality. 

Adverse effects With chronic use, procainamide causes a high incidence of side effects, including a reversible lupus erythe-matosus-like syndrome that develops in 25 to 30% of patients. Toxic concentrations of procainamide may cause asystole or induction of ventricular arrhythmias. Central nervious system (CNS) side effects include depression, hallucination and psychosis. With this drug, gastrointestinal intolerance is less frequent than with quinidine. 

Procainamide and quinidine cdrnmonly cauie Gl upset (nausea, vomiting, diarrhea) and hj otension. Less commonly, procainamide is associated with agranulocytosis end iupus-Uke syndrome Additional side effects of quinidine include thrombocytopenia and cinchonism. ... 

Table 12.2 Management of the side-effects of quinidine therapy in the horse ...

Procainamide does not produce serious side-effects like quinidine and lidocaine (lignocaine) however, it is a negative inotrope and may cause hypotension QRS prolongation and ventricular arrhythmias can occur at high doses (Muir Mcguirk 1987). 

Lidocaine is indicated for the treatment of ventricular tachycardias (Fig. 12.4). Electrolyte abnormalities should be investigated and corrected prior to lidocaine administration. Lidocaine is administered as i.v. bolus doses of 0.5 mg/kg every 5 min, up to a total dose of 4 mg/kg (Table 12.3) (Muir Mcguirk 1987). Although lidocaine is used frequently in anaesthetized horses, quinidine gluconate or procainamide are preferred in conscious horses because they do not produce CNS side effects. 

Exert four actions similar to phenothiazines M block, alpha block, sedation, and decrease seizure threshold, plus greater cardiotoxicity ( quinidine-like ), a major mortality factor in OD. Triad ( 3 (is ) coma, convulsions, and cardiotoxicity. Autonomic side effects, additive sedation with other CNS depressants, and weight gain commonly occur with TCAs. 

Answer E. Increased sympathetic activity is a major problem in hyperthyroidism and is best managed by use of beta blockers, which can offset cardiac stimulatory effects. Propranolol has an ancillary action in thyrotoxicosis in that it prevents conversion of T to Tj via its inhibition of 5 deiodinase. Amiodarone causes difficult-to-predict adverse effects on thyroid function and would not be appropriate in a patient with hyperthyroidism. Quinidine is a class lA antiarrhythmic, which is associated with tachycardia as a side effect. Digoxin is not ideal because of its complex actions on the heart, which include both inhibition and stimulation. 

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