Never had a problem w any abx in this family until the prednisone. There's a good bit of data on spontaneous tendon rupture from abx but most of it is associated w fluoroquinolones.

The orthopedist said any abx can do it but less likely w the penicillin. Long term pred is a known risk factor for spontaneous tendon rupture.

"Classic risk factors for spontaneous rupture of tendons include steroid therapy, hypercholesterolemia, gout, rheumatoid arthritis, advanced age, long-term dialysis, and renal transplantation.[1,6-9] Since 1983, fluoroquinolones have also been reported to be associated with disruption of tendons.[7,9,10]"

I am the poster child for bad pred side effects thou.