Do fluoroquinolones need to be renally dosed?

Depends on which one. Moxifloxicin (Avelox) no.

Ciprofloxacin and levofloxacin yes.

When GFR < 50. Decrease dose by 1/2. When GFR < 10. Decrease dose by 1/4.

Here's a GFR calculator, compliments of MD Calc, or as a general approximation, GFR < 50 when:

• female, > 70 y/o, Cr > 1.1
• male, > 70 y/o, Cr > 1.5
  

and < 10 when:

• female, > 70 y/o, Cr > 4.5
• male, > 70 y/o, Cr > 5.0

Of note, dialysis does not remove ciprofloxacin or levofloxacin.


Source

Hooper, David. "Fluoroquinolones" Up to Date. 1 Feb 2008.