Both drugs can lower blood pressure through different pathways. Amlodipine relaxes your blood vessels, while tramadol can affect the central nervous system and occasionally cause 'orthostatic hypotension' (a drop in blood pressure upon standing). Additionally, both are processed by the liver, which can sometimes lead to one drug affecting the levels of the other.
This is a companion discussion topic for the original article at https://patient.info/medication-interactions/amlodopine-and-tramadol-interaction