Procainamide Levofloxacin

The OAT family of transporters can be inhibited by probenecid. If a substrate of this family of transporters, such as penicillin, is administered concomitantly with probenecid, the dmg can have decreased renal secretion, with a resulting increase in the plasma penicillin concentration. Cimetidine is an inhibitor of members of the OAT, organic cation transporter (OCT) and OATP families of transporters This inhibition has been shown to result in a decrease in the renal excretion of substrates such as procainamide and levofloxacin, resulting in increased plasma concentrations of these dmgs. 

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. 

The probable reason for the interaction is that levofloxacin, ofloxacin and to a lesser extent ciprofloxacin, inhibit the secretion of unchanged procainamide by the kidney tubules via renal drug transporters. Levofloxacin also appears to inhibit the secretion ofV-acetylprocainamide. 

Bauer LA, Black DJ, Lill JS, Garrisc J, Raisys VA, Hootc TM. Levofloxacin and ciprofloxacin decrease procainamide and N-acetylprocainamide renal clearances. Antimicrob Agents ChemoOter (2005) 49,1649-51. 

---