It must have been difficult for you and your family. I would concentrate briefly on the problem and then mention about interventions.
The prescription drug abuse(Benzos) is not uncommon but can equally problematic as the illicit substance abuse
. The benzodiazepines have two main problems. 1. Tolerance (the person develops tolerance to the drug,means he needs more strength to get the same effect after using for longtime) 2.Dependence (The person becomes dependant on the drug,making the person addicted to tot he drug, making it difficult to come off ).This is more common for short acting medications like Xanax because of the short half life which means the drug would stay in the body for short period making the person to crave for it more.
Coming to the management issues--
1. It is atmost important for all members of the family to be consistent in the message that it is NOT acceptable and try not to ignore or allow him to split the family opinion.
Discuss rules, expectations, and consequences in advance.
If a rule is broken, be sure to enforce the consequences. This teaches him to take responsibility for his actions.
Give praise when he follow rules and meet expectations.
2.Short discussions go a long way. Engage him in a conversation. Ask what he know, how he feel, and what he think about the issue. If he has been to the rehab before,I am sure he might have learnt some good techniques but putting them in to practice is the most important thing.
3.It is important to find out the source of medications. If he is abusing Benzodiazepines, it might be unlikely to get these from PCP on a regular basis. So, it is important to ask him because if he is buying off street the quality and safety is important thing to consider.
4.It is also important for him to be seen by a Psychiatrist to look for any co morbid psychiatric illness if present as sometimes the person might choose to self medicate than accepting the problem and seeking help.
5.Please note that both your parents might have to change their styles of interaction(one being strict and other being too soft . But it is not easy because it might be ingrained in the personality.so, at least what they can do is have a discussion between them about this specific issue,agree for a common strategy of action and stick to the plan, Not allowing him to manipulate them as can happen sometimes)
6.The positive news is if he is keen to seek help,wanting to change his behavior or drug seeking habit, it can be done with the help of PCP,Drug counselor and Psychiatrist if necessary. The extent of the problem would be assessed first,then the doctors would discuss with him and decide whether it is safe to wean him off gradually in the community with the help of the family or needs admission.
I am sure by now you might have noticed that all I have mentioned above have some for of involvement from him which is a key.
For you to choose writing letters might be fine but try not to attack the personality but be factual in the content of the letters,how it is effecting him and the family,how he was before all this,why you thought he relapsed and you would love to see the old brother who was a completely different person Etc.
Please do not hesitate to contact me if you require more information.
I wish him all the best.
I hope you had a lovely Christmas and happy new year.
Please be mindful that you are doing what you can.
If you find the answer helpful,please provide positive feedback.