Is it considered forbidden or usury to pawn gold for a certain amount, then reclaim it for a larger amount?

The transaction mentioned is usury (riba), and the questioner must repent from it. It is not permissible for him to pay usury, which is the amount exceeding the original debt, due to the hadith: "Allah has cursed the one who consumes usury and the one who feeds it to others." Paying the usurious increase falls under "the one who feeds it to others." He should strive to release his pledge without paying usury.