Dear Andy,
in the EMA appendix 1, there are three nitrosamines listed which are correlated with macrolides,
N-nitrosodesmethylazithromycin, N-nitrosoazaerithromycin and N-nitrosodesmethylclarithromycin. The first two has been charactarized as NMI (through in-vivo study). The same charactarization has been given also for the nitrosamine of clarithromycine but through read-across and weight of evidence approaches based on the N-nitrosodesmethylclarithromycin. Actually, as it has been reported in this forum before some time, this could be the beginning of setting AI limits for whole category of compounds using the in-vivo data of a representative surrogate.
regards,
Christos