Schizophrenia. And does not take any.

My mother suffer from positive symptoms of schizophrenia for the past 30 years We have been able to get her on medicine on and off. Now she does not want to go to a doctor and seems to be behaving more irrationally and suspicious. Is there a medicine we can use which can not be detected and we can get her to a doc for treatment. We did get one such liquid 15 years back which made her sick and she herself asked to go to a doctor Please help as you can imagine our entire family is disrupted and we really want to help our mother but there is no way out. She gets abusive and uncontrollable at the mention of a problem and says she is fine and becomes adamant to the point of hysteria at the mention of doc She is suspicious of all medicines and does not take any.