[outofsalt]

"Throw away any unused tetracycline (all cycline antibiotics) when it expires or when it is no longer needed. Do not take this medicine after the expiration date on the label has passed. Expired tetracycline can cause a dangerous syndrome resulting in damage to the kidneys." (Fanconi syndrome) https://www.drugs.com/tetracycline.html

[Wuli]

The initial case report, involving a form of the drug that is no longer used, was published in Annals of Internal Medicine in 1963.

There were a handful of subsequent incidents, leading to a longstanding warning about taking that drug when it is outdated.

A 2004 review of the literature on tetracycline and similar antimicrobials suggested that it might be difficult to determine when the kidney ailment is caused by such a drug.

https://www.ncbi.nlm.nih.gov/pubmed/15113987

[reformedliberal]

Expired tetracycline can cause a dangerous syndrome resulting in damage to the kidneys.” (Fanconi syndrome) https://www.drugs.com/tetracycline.html
_____________________
After extensive discussion w/colleagues, my vet said this is exaggerated and based on an inadequate study.

I have no pharmaceutical background, so IDK.