This brief report provides a practical overview of Medical Science Liaisons and Field Medical Affairs for advanced practice registered nurses. It describes MSLs as non-promotional scientific resources who support evidence-based clinical practice through scientific exchange, insight gathering, research collaboration and stakeholder engagement. The paper explains the firewall between MSLs and sales representatives, including differences in objectives, metrics and handling of off-label scientific questions. It then broadens the MSL role across professional organisations, academia, healthcare systems, payers, clinical-trial sites and internal cross-functional partners. For APRNs, the message is two-way: MSLs are resources that can support clinical practice, and advanced-practice clinicians may themselves bring highly relevant skills into Field Medical roles.