A 50-year-old woman experienced acute renal failure after receiving contrast dye for an imaging study. Her estimated creatinine clearance is now 20 mL/min. Her medications include:
* Piperacillin/tazobactam 4.5g intravenously every 8 hours
* Azithromycin 500 mg intravenously daily
* Famotidine 40 mg orally twice daily
* Enoxaparin 40 mg subcutaneously daily
* Metoprolol succinate 100 mg orally daily
Which drugs require dose reduction due to acute renal failure?