Though eflornithine is an effective and specific inhibitor of ODC, its efficacy is somewhat limited and variable, probably because of its low skin penetration, a poor target tissue accumulation, and the rapid turnover rate of ODC enzyme. The result is a wide range of efficacy from nearly no effect in some subjects to as much as 70% hair reduction in others. Because eflornithine is a highly hydrophilic molecule with no inherent affinity for penetrating the lipid-rich skin structure, various penetration enhancers have been evaluated to increase its penetration. Agents such as cis-fatty acids, fatty alcohols, fatty acid esters, select terpines, and nonionic surfactants have shown good penetration enhancement ability in in vitro human-skin model [62]. Whether this in vitro effect will translate into efficacy benefits in humans is yet to be studied.
A mean facial hair-growth reduction of 47% by Vaniqa [58] implies that women must use adjunctive hair-removal methods to maintain a hair-free look. The conventional hair – removal methods such as shaving, epilation, and depilatory creams only provide an adjunctive-use benefit without a true synergy. Further, this needed adjunctive use does not necessarily reduce the overall effort women must put into managing their facial hair. Laser hair removal with its own limitations, as a standalone modality, has the potential to provide synergy with Vaniqa in managing facial hair growth.