This code system http://smart.who.int/pcmt/CodeSystem/ProductRelationship defines the following codes:
Code
Display
contains
This relationship is used to represent some packaging packgaing, assemblage of kits or other physical containment of products. The Product contains the associated Products that are referenced
vial_contains
This relationship is a speciialization of the #package-contains concept which represents that the product is a vial
inner_pack_contains
This relationship is a speciialization of the #package-contains concept which represents that the product is an inner pack
case_contains
This relationship is a speciialization of the #package-contains concept which represents that the product is a case
pallet_contains
This relationship is a speciialization of the #package-contains concept which represents that the product is a pallet
equivalent
This relationship indicates tha product is equivalent to the referenced product, for example such as with duplicate entries in a catalogue for the same phtsical item.