The present invention provides a formulation comprising a lipid matrix; at least one thiolated antioxidant; at least one bioactive agent; and optionally at least one chelating agent. The bioactive agent may be a gonadotrophin-releasing hormone (GnRH) agonist; a gonadotrophin-releasing hormone (GnRH) antagonist; a luthenizing hormone releasing hormone (LHRH); and/or a luthenizing hormone releasing hormone (LHRH) related peptide.