Part XVIIIA of the Drug Tariff contains a list of drugs, medicines and other substances that cannot be ordered under the NHS.
The list is made up of specific products and not generic drugs. Only those items specified would be disallowed if prescribed.
Items in Part XVIIIA are also referred to as Schedule 1 drugs.
The decision to add a product to Part XVIIIA is made by the Department of Health and Social Care and published in Schedule 1 of the National Health Service (General Medical Services Contracts)(Prescription of Drugs etc.) Regulations 2004.
This is reproduced in Part XVIIIA of the Drug Tariff.