It would depend on the medication. The meds should have a recommendation.
You should also be monitoring the water quality just in case you need to do one to get parms under control.
Agree with above, meds should have a schedule and instructions on back, for instance, furan-2 has you do 2 doses over a 24 period and then a 25 percent water change after another 24 hours, just depends on the meds, also, as stated above you also need to monitor water quality, ammonia and such.
Agreed— follow typical med-manufacturer’s instructions for water changes. For copper, however, if you are doing your own tests for ammonia, you will need a SeaChem Ammonia Badge (about $7 on Amazon) as the copper will throw off other ammonia tests (such as API).