There can be a facilitation of spirit meddler possession through heavy narcotization of a person, which is not uncommon when there are painful, chronic illnesses reaching the lethal stage. But keep in mind that it is almost certain that all such individuals are already highly infested, having undergone such a long period of difficulty, and struggle, and despair, and fear, from facing their eventual fate. And often the emotional turmoil of their prior life leading up to the onset of their illness in the first place, was likely to favor spirit possession and make them vulnerable.
So this should never be an overriding consideration to withdraw medication from someone that can keep them from suffering, as that is a cruelty inflicted on a hapless sufferer that will have karmic consequences. This is often happening with over-concern about prescription drug use and abuse, with the pendulum swinging back and forth, to allow excess and then unnecessary over-constraint, to avoid the semblance of frivolous use and its risks, and reckless disregard for potential harm, and the impression of indulging in those who seek the experience of pleasure and have no true medical need, and thereby causing an ongoing sense of confusion and backlash, harming many individuals, in both directions.
This is a quite difficult challenge to manage with accuracy, and an ideal balancing of the issues at stake. Things can always be improved, but denial of pain relief, solely to prevent a potential abuse, is harming the person before the fact, and in a quite grievous way. Protecting people from themselves is often the choice of governments and their regulations, and their sense of entitlement to be the arbiter of many human undertakings, and they often cause harm with the good, by being arbitrary, ill-advised, or ill-equipped to understand the nuances of human need. And so many will suffer needlessly through over management. This will improve with more insight and a higher-level perspective when more are in divine alignment.