Is Keflex (Cephalexin) Left Out Of Refrigerator Safe To Use?

In our latest question and answer, the pharmacist discusses how long Keflex (cephalexin) suspension is good if left out of the refrigerator.

Is Keflex (Cephalexin) Left Out Of Refrigerator Safe To Use?
May 31, 2018

Just asked

I left my sons Keflex (cephalexin) suspension out for 24, but not near the sunlight or high temperatures. The bottle says it needs to be refrigerated. Does it still work?


Pouring KeflexWhile the prescribing information for Keflex (cephalexin) suspension states that it must be refrigerated, most available data indicates that if left at room temperature inadvertently, it will still be stable and safe to use for at least 24 hours. However, be sure to return it to the fridge as soon as possible.

Is Keflex (Cephalexin) Suspension Stable At Room Temperature?

One source states that Keflex (cephalexin) suspension can be left out at room temperature for up to 24 hours with no effect on stability. Room temperature is defined as 68 to 77 °F.

Another large study tested the stability of Keflex (cephalexin) suspension in polypropylene oral syringes, stored at various temperatures (-4°, 39.2°, 77°, 104°,140°,176° Fahrenheit). The study found that at temperatures of -4°, 39.2° and 77° Fahrenheit, Keflex (cephalexin) suspension was stable and did not degrade over a 90 day period. The study concluded:

"Cephalexin monohydrate suspension reconstituted from powder as a suspension and repackaged in clear polypropylene oral syringes was stable for 90 days when stored under ambient, refrigerated, and frozen conditions."

Yet another study reported similar results regarding the stability of Keflex (cephalexin) suspension. They tested the stability of the suspension after 7 days of storage at room temperature and after 14 days of storage under refrigeration. In both cases, the suspension was tested and found not to have any appreciable degradation:

"From a clinical point of view, the storage conditions applied did not affect dissolution or chemical stability of [cephalexin] oral extemporaneous suspensions."

Based on the information available, leaving your Keflex (cephalexin) suspension out at room temperature for 24 hours will likely not affect the stability of the medication. It should be safe to use. Nevertheless, be sure to speak with your local pharmacist or doctor regarding your options.

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