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.
I left my son's Keflex (cephalexin) suspension out for 24 hours, but not near the sunlight or high temperatures. The bottle says it needs to be refrigerated. Does it still work?
Jun 04, 2022- If Keflex suspension is left out at room temperature inadvertently, it will likely remain stable and safe to use for at least 24 hours.
- You should return the medication to the refrigerator as soon as possible after it has been left out.
- If you have concerns about whether your specific bottle is still safe to use, check with your pharmacist or doctor.
Hello and thanks for reaching out1
While 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."
Final Words
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.
Thanks again for your question!
References & sources
- Keflex Prescribing Information — AccessFDA
- Assessing palatability of medicines in children — ResearchGate
- Stability of cephalexin monohydrate suspension in polypropylene oral syringes — PubMed
- Dissolution Stability of Cephalexin Extemporaneous Suspensions During an Accelerated Stability Study — Dissolution Technologies
Glossary — Terms in This Answer
- Cephalexin
- An antibiotic medication belonging to the cephalosporin class used to treat bacterial infections.
- Suspension
- A liquid medication form where solid particles are mixed throughout the liquid but may settle over time.
- Stability
- The ability of a medication to maintain its strength and effectiveness under specific storage conditions.
- Refrigerated
- Kept at cold temperatures, typically between 36-46°F, to preserve medication quality.
- Polypropylene oral syringes
- Plastic measuring devices used to deliver liquid medications by mouth.
- Degradation
- The breakdown or weakening of a medication's chemical structure and effectiveness over time.
- Reconstituted
- Mixed back together with liquid to create a usable medication from its original powder form.
- Extemporaneous
- Prepared or made up at the time it is needed, rather than pre-manufactured.
Dr. Brian Staiger, PharmD
Doctor of Pharmacy, board certified clinical pharmacist (BCPS), American Herbalist Guild, Medication Therapy Management certified
Brian Staiger, PharmD, BCPS, is a licensed pharmacist with more than 13 years of experience across retail pharmacy, clinical pharmacy, medication safety, pharmacy program development, and healthcare administration. He is the founder of HelloPharmacist.com, where he helps patients...
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