No, codeine can't be said to be bad for the user if prescribed by the chemist for the purpose it is meant for. As you must know codeine is a medicinal drug that is used for cough and catarh to help relief congested nasal passage.
Codeine as a cough syrup can be helpful in the aspect of health improvement, but on the other hand, it also has its side effects inspite the fact it been used medicinally. However, it can make one to fall asleep easily as it is known to be a drowsy drug(sleep inducer). That's why you are advised to only take it before going to bed.
Surprisingly, it must interest you to know that codeine can be abused as intoxicant,i.e, to provide some sort of euphoric effects as it with hard drugs. In other words, codeine can be used as an abusive drug whereby the the main purpose it was meant to serve is being compromised.