having four such rings, e.g. porphine derivatives, bilirubin, biliverdine (hemin, hematin A61K31/555)

Full Title

Medicinal preparations containing organic active ingredients > Heterocyclic compounds > having nitrogen as a ring hetero atom, e.g. guanethidine or rifamycins > having five-membered rings with one nitrogen as the only ring hetero atom, e.g. sulpiride, succinimide, tolmetin, buflomedil > having four such rings, e.g. porphine derivatives, bilirubin, biliverdine (hemin, hematin A61K31/555)