anatomical therapeutic chemical classification system apotex asia bapta bioavailability biological half-life cas registry number canada chelation therapy chemspider chemical formula deferasirox deferoxamine digital object identifier dimercaprol dimercaptosuccinic acid drug drug metabolism edta europe excretion hospital for sick children iron kidney lipoic acid oral penicillamine pentetic acid pubchem regulation of therapeutic goods researcher route of administration simplified molecular input line entry specification united states