Is it permissible to perform ghusl while wearing a contraceptive patch, by analogy with the rulings on splints, knowing that it is a necessary medicine and remains on the body for a week?

Using contraception is permissible when there is a need, subject to legitimate Islamic guidelines. If the contraceptive patch covers a part of the outer body, it must be removed when performing ghusl (definition) (ritual bath) after menstruation or janabah (definition) (state of impurity requiring a full bath) to ensure that water reaches all parts of the body. It does not take the ruling of a jabirah (splint/bandage) because there is no harm in removing it and washing the skin underneath.