In my experience, most plans require prior authorization for unlisted drug codes (J3490, J3590, J9999), generally because the codes are being used for new drugs with no utilization history. Did you try to obtain authorization initially and were told it wasn't needed? If so, I would enlist the payer rep's help to get these reprocessed and point out the staff giving out that information need to be re-educated. If you did not check the authorization requirements before treating, you can try to appeal based on medical necessity but your success will depend on your contract language. Either way, if this is a recurring treatment, you need to make sure your precert team contacts the insurance to get an approval in place for future treatment.