A medicinal product is granted special container status in cases where it's not practical to split an original pack.

Where the quantity ordered by the prescriber is less than the actual pack size and the product is considered a special container, you must supply the special container or a combination of containers nearest to the quantity ordered and endorse the prescription with the number and size of these containers.

If the quantity ordered falls exactly between 2 containers, you must dispense to the nearest complete container, rounding down unless the quantity ordered is more than halfway into the second pack size.

More information can be found in Part II, Clause 10B of the Drug Tariff