Data on the effectiveness of Medicis Pharmaceutical Corp’s wrinkle-filler Restylane as a lip plumper may be unreliable, US-based drug reviewers said in documents released Monday ahead of a panel meeting to discuss the merits of the treatment.

The FDA staff cited concerns that included the lack of a control arm in study data that would help compare the drug’s efficacy with a placebo or a rival treatment, the small size of the study, and the use of a non-validated scale to assess the drug’s effectiveness.

The reviewers also expressed concern on whether the safety and effectiveness of Restylane for lip augmentation were adequately tested in people of color.

Restylane is already approved to fill out facial wrinkles, such as laugh lines, and is also used off-label to augment and contour lips.

The safety outcomes of the lip trial were consistent with the findings of the pivotal study, which formed the basis of the drug’s regulatory approval.