One of the issues you are touching on is what we refer to as Medication Reconciliation. At least in the US, the standard of care is to verify the current medications a patient is taking at every visit - whether it be an office visit, ED visit, or a hospitalization. Our local pharmacies also play a part in checking for medication interaction. This does not extend to over the counter medications however.
The US is the same in that the patient owns their own information. However, private entities are charged with the responsibility with holding and securing that data. Unfortunately, there is no central repository for it here.
More advanced systems in the US do allow for data access via phone. But it is not uniformly available or applied.