Pack any regular medication in its original, labelled packaging, along with a letter from your vet stating the medication, dosage, and that it's for the named pet's own treatment. This single document resolves most questions at a border or airport check.
If the medication is a controlled substance — certain sedatives or strong pain relief, for instance — check Switzerland's import rules for that specific drug in advance, since controlled substances often require separate documentation beyond a standard vet's letter, and rules can differ from the EU's.
Pack enough medication to comfortably cover the full trip plus a few extra days, since finding an exact equivalent brand at a Swiss pharmacy or vet on short notice isn't guaranteed, even though the country's pharmacy network is excellent.