"(11) The Minister shall only make regulations under this section to provide for a prohibition and exception to the prohibition referred to in subsection (2)(l) if the Minister, after having had regard to the nature and purpose of the medicinal product, or class of medicinal products, concerned (including any deleterious effects which may arise from the misuse thereof), is satisfied that the prohibition and exception to the prohibition is in the best interests of the persons to whom the medicinal product, or class of medicinal products, as the case may be, is usually administered.