These Regulations amend the National Health Service (General Medical Services Contracts) (Prescription of Drugs Etc.) (Wales) Regulations 2004 (S.I. 2004/1022 (W. 119)) (“the principal Regulations”), which make provision as to the drugs, medicines or other substances that may be ordered for patients in the provision of medical services under a general medical services contract (“GMS contract”) within the meaning of section 42 of the National Health Service (Wales) Act 2006 (c. 42).