can involve skin, scalp
, nails and joints. It is quite common in psoriasis to find nail involvement. The horizontal ridging that you are having is a psoriasis induced change. It is seen in almost 50 percent cases of skin involvement. As far as severity is concerned, if nails are involved chance of joint involvement might be more.
I haven't heard of any medicine oxytinin in India. However it could be oxetine, an antidepressant given to calm mind.
Hope that answers your query. Take care.