Fanny, if you take the medication to your pharmacy, they will destroy it safely. As has been said, they are not allowed to reuse them for health and safety reasons.
I often have to return unused medication, due to them being unsuitable. It is such a waste, but obvious why they can't be reused.
Although Methotrexate would probably have helped my RA, it is unsuitable for anyone with lung problems.
Those with both lung problems and RA , should have their lungs monitored, due to the possibility of a terminal condition called, Rheumatoid lung.
I have experience of this on a few occasions. Fortunately, much to my relief, it has just been a flare up of my lung conditions.