Your question illustrates well the many challenges of auxiliary/non-investigational medicinal products!
Whilst you have referenced Regulation (EU) No 536/2014, be aware that this is not yet in effect and that the current legislation is Directive 2001/20/EC and the national legislation put in place under this. The approach may need to vary from Member State to Member State. Further, the scope of Directive 2001/20/EC and Annex 13 is investigational medicinal products; they do not directly deal with non-IMPs. Regulation (EU) No 536/2014 will address this gap when it comes into effect. The further guidance “Guidance on IMPs/NIMPs”, should also be noted, however this is silent with regards to labelling requirements https://ec.europa.eu/health/sites/health/files/files/eudralex/vol-10/imp_03-2011.pdf
Given that Directive 2001/20/EC and Annex 13 do not cover non-IMPs, Chapter X and Annex VI of Regulation (EU) No 536/2014 are probably the best sources of information on EU regulatory expectations for the labelling of auxiliary/non-investigational products.
There is a general expectation that labelling particulars appear in the official language(s) of the Member State to which the product is supplied. This makes it difficult to centrally source non-IMPs intended to be supplied as commercial packs: Even if the product has a central EU authorisation, there will be different packs (with the appropriate language) intended for each Member State. It may be possible to use English labelling and SmPC (or PIL) if the non-IMP is dosed at the study site, but you would need to check national requirements. Under 2.1.6, Other issues, section 25 of CT-1 states that 25. “The Commission encourages national competent authorities to accept the English language in their communication with applicants and for documentation which is not destined for the public or the clinical trial participant, such as scientific documentation”. Which may be used to support use of English language documents
Both Regulation (EU) No 536/2014 and Directive 2001/20/EC are EU legislation and all references within them to ‘authorised product’ relate to product authorised within the EU.
If you provide product outside the EU, then the local requirements of the destination country need to be met, not those of the EU legislation.
Sorry for the lengthy reply!