In general, vitamins have been used extensively in cosmetic products for some time. One of the relatively newer entrants is niacinamide (nicotinamide) and the amide form niacin (nicotinic acid), water soluble members of the vitamin B complex. Physiologically, the primary biochemical function of dietary niacinamide and niacin is to be used as precursors for the biosynthesis of the key enzyme cofactors nicotinamide adenine dinucleotide (NAD) and the phosphorylated derivative (NADP). These cofactors play a critical role in serving as reducing and oxidizing equivalents for a host of enzymatically catalyzed biochemical reactions.
It has been hypothesized that formulations containing niacinamide can restore the reduced levels of NAD(P)H in keratinocytes and fibroblasts from older, aged, and photo- damaged skin to levels approximating those present in younger-aged skin [14]. This normalization to a homeostatic state is thought to allow cells to function at optimal capabilities, particularly as related to metabolic competence. While precisely how the dinucleotide cofactors might contribute to all these effects has not been elucidated, several specific actions of niacinamide have been described [15-17].
The published literature on topical niacinamide has shown the ability for it to elicit a range of effects [15-17] including reduction in the appearance of fine lines and wrinkles (Fig. 15.3), appearance of evening skin tone, reduction in pigmentation, and improvement in skin barrier. These data were obtained from double-blind, placebo-controlled, left-right randomized studies and was shown to reduce the overall appearance of skin fine lines/ wrinkling after 8-12 weeks of treatment.
While it would be anticipated that niacin and esters thereof should be able to mimic niacinamide, there are limitations to their topical usage due to the rapid and acute vasodilation that can be elicited. This onset of redness is a negative side effect for the cosmetic consumer. It is presumed that there is rapid hydrolysis of the esters, yielding free niacin. Since the mid-1990s, there have been several publications reporting the synthesis and biological properties of synthetic ester derivatives that can have varying water solubility properties. The longer chain esters (e. g., myristoyl-nicotinate) are apparently more resistant to
this hydrolysis, and thus appear to be more suitable for topical use. It has been reported that myristoyl-nicotinate can elicit a range of skin benefits at the 1-5% dose range [18].