Procainamide Gatifloxacin

Concurrent use of the fluoroquinolones with theophylline causes an increase in serum theophylline levels. When used concurrently with cimetidine, the cimetidine may interfere with the elimination of the fluoroquinolones. Use of the fluoroquinolones with an oral anticoagulant may cause an increase in the effects of the oral coagulant. Administration of the fluoroquinolones with antacids, iron salts, or zinc will decrease absorption of the fluoroquinolones. There is a risk of seizures if fluoroquinolones are given with the NSAIDs. There is a risk of severe cardiac arrhythmias when the fluoroquinolones gatifloxacin and moxifloxacin are administered with drains that increase the QT interval (eg, quini-dine, procainamide, amiodarone, and sotalol). 

Cardiac toxicity Moxifloxacin and gatifloxacin have been shown to prolong the QT interval of the electrocardiogram in some patients. Avoid in patients with known prolongation of the QT interval, patients with uncorrected hypokalemia, and patients receiving class lA (eg, quinidine, procainamide) or class III (eg, amiodarone, sotalol) antiarrhythmic agents. 

Clinically important, potentially hazardous interactions with abacavir, amiodarone, bretylium, chlorpromazine, ciprofloxacin, disopyramide, enoxacin, fluphenazine, gatifloxacin, lomefloxacin, mesoridazine, moxifloxacin, norfloxacin, ofloxacin, phenothiazines, procainamide, prochlorperazine, promethazine, quinidine, quinolones, sotalol, sparfloxacin, thioridazine, trifluoperazine... 

Ofloxacin and levofloxacin cause moderate increases in the serum levels of procainamide, whereas ciprofloxacin has a lesser effect However, the ECG appears to be unaltered in studies in healthy subjects given these quinolones with procainamide. An increased risk of torsade de pointes would be expected if procainamide is used with gatifloxacin, moxifloxacin, or sparfloxacin, and possibly levofloxacin. 

Of the quinolones used clinically, gatifloxacin, moxifloxacin, and sparfloxacin are known to prolong the QT interval (see Table 9.2 , (p.257)) and would be expected to increase the risk of torsade de pointes arrhythmias when used with procainamide. These quinolones should probably be avoided in patients on procainamide (see also Drugs that prolong the QT interval + Other drugs that prolong the QT interval , p.257). 

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