That's so simple it's coded into all prescribing systems and even written in paper prescribing manuals. The issue is that while some interactions are harmful,

That's so simple it's coded into all prescribing systems and even written in paper prescribing manuals. The issue is that while some interactions are harmful, many are harmless and some even beneficial, but knowing the context that influences this range of effects is based on more than the contents of the prescription. Judgement and wider knowledge of the patient is required. People are still good at that but not infallible. I'm an ex pharmacist. Drug interactions, overdoses and plain wrong drug mistakes abound even in the age of computerised prescribing. One of my bosses has a photo of her and a child's prescription fixed to the wall of a paediatric consultant who would have a killed a child if a pharmacist, my boss, had not queried a prescription. Checking each other's work is essential in many industries but more so in healthcare.