Most catfish and loaches (including Corydoras) don't have a swim bladder.
There's no such thing as swim bladder medication. Any shop trying to sell you specific swim bladder medication is selling you snake oil.
Post a video of the fish so we can see it swim.
Most swim bladder issues are caused by air in the fish's intestine that cause the fish to float when it stops swimming. This occurs when fish are fed a lot of dry food or food that floats on the surface. The fish take in air when eating dry food or food at the surface and swallow the air. The air goes through their digestive tract and can cause them to float around the tank. Eventually the air passes out the fish's butt (yes fish fart) and the fish swims normally again.
On occasions fish will have a swim bladder problem that causes them to float when they stop swimming. However, this is uncommon. If you think this is the issue, stop feeding dry food for a week and offer the fish live or frozen (but defrosted) foods. If the problem is fixed after a few days without dry food, then it was caused by air. If the problem still occurs after a week without dry food, then it probably has a swim bladder problem.
If a fish that has a swim bladder, sinks to the bottom when it stops swimming, then there is a swim bladder issue.