i found a pliva 563 in my little brothers room?
Dark Yellow, Round, Unscored, Pliva one side, 563 other side....10mg muscle relaxant
This pill is CYCLOBENZAPRINE 10 MG
a generic version of Flexeril
Imprint Code PLIVA / 563
Description yellow, round tablet
Cyclobenzaprine is a muscle relaxant is used to relieve pain, tenderness, and limitation of motion caused by muscle spasms.
Info at https://www.drugs.com/MTM/cyclobenzaprine.html