What Causes Addiction Towards Ibuprofen And Cocodamal?

hello my son who is 41 is addicted to I ibuprofen and cocodamal he hides the fact his taking these ,,we all so worried his been addited to other drugs like pain killers, athetimins over the years and alcohol ,,he uses different chemist throughout the area ,and get but up too 3 packs aday and takes around 16 at a time he also goes out for 3 or 4 hours at a time ,,and can just go sit in his car wile he takes these tablets ..we never know where he goes either ,I am in close contact with his girl friend so we know what his up to ..altho he denies and lies about his use of these pills ,,I have spoken to him in past about this and says his weaning himself off of them but that was over 2 years ago ,,,what can we do to help him as were so worried his going to end up killing himself ..I might add his taking antidepressants too off his doctor ..can you help please or advise us ..thanking mrs s hawes