USE

USE[<amount>] "<Potion>" [<unit-id>]
USE[<amount>] "<Item>" [...]

Use the indicated alchemical potion.
The unit number may only be specified for duncebun.
Without specifying an amount, only one potion is used.
You can use a potion multiple times to extend the effects to more than 10 people or to increase the number of weeks the effect lasts.
For duncebun, the duration is limited to 10 weeks per person.

There are other items than potions that can be used.
These include Antimagic Crystal and some faction items (Christmas).
These can have additional parameters, which are specified in the item description.