TOPROL is the brand name of metoprolol.Atenolol and metoprolol are the drugs belong to the group called B-Blockers.There is not much difference between two drugs as both are specific b-2-blockers (subclass of B-Blockers).These are used to traet high blood pressure,chest pain(angina),heart failures and arrythmias.
Atenolol is excreted mainly by kidney while metoprolol is metabolised mainly by liver. Therefore, the dose of atenolol should be reduced in patients with renal impairment while the dose of metoprolol should be reduced in patients with liver impairment.
Both of them can be used to treat hypertension, but in different dose. They are pretty similar when it comes to side effects.