Remove custom fields via API?

I've got a script that dynamically generates a set of custom fields and adds them via the api to devices. Is it possible to remove fields via the api - I don't see anything in the documentation about it.

For example I have a set of fields like Raid1=250GB RAID2=500GB. If we change the server to a single RAID array of 300 GB, then the script will of course update the RAID1 field to = 300GB but then there's RAID2=500GB still hanging around. it seems the simplest way (formthe scripts perspective) would be to remove all custom fields for a device and then just re-add them with new values. Is there any way to do this?