Ani anti-depressant takes around three weeks to balance out in the pateint's system, and side-effects of varying degrees can crop up, and then subside.
It may be that this medication is not suitable for your uncle - it wasn;t for me - and not all AD's suit all people. i would certainly give it a chance to work, and sudden cessation will do more harm than good.
You should never alter medication without medical advice and agreement - so see your GP a.s.a.p. or at least have a conversation by phone.