Recently several babies exposed to methadone and benzodiazapines have been overly sleepy with minimal interest in feeding, extremely gassy and are over a month of age and already off morphine and clonidine treatment for NAS.
to may no ledge there is no paper specifically address G-Tube placement in NAS. There are only prevalence studies vlbw infants, see.
Khalil, S. T. et al. (2017). Outcomes of Infants With Home Tube Feeding: Comparing Nasogastric vs Gastrostomy Tubes. Journal of Parenteral and Enteral Nutrition, 0148607116670621.
Hoogewerf M, Ter Horst HJ, Groen H, Nieuwenhuis T, Bos AF, van Dijk MWG. The prevalence of feeding problems in children formerly treated in a neonatal intensive care unit. J Perinatol. 2017;37(5):578-84.
To my knowledge opiate use or withdrawal syndrome were not systematically addressed. It would be a very interesting research question.