The management of cancer pain presents manifold challenges: even though background pain is adequately controlled, patients frequently experience episodes of acute pain exacerbation known as breakthrough cancer pain (BTcP). The characteristics of BTcP are a rapid onset, a short duration, and a severe intensity. An innovative sublingual fentanyl citrate formulation (Vellofent®) has been developed to target BTcP. The new formulation allows to increase the solubility of fentanyl and to provide optimal oromucosal conditions for rapid drug absorption, thus featuring a shorter time to onset of pain relief (from 6 minutes post-administration).