Molecular and Cellular PharmacologyInteraction between ciprofloxacin and melanin: The effect on proliferation and melanization in melanocytes

There have been described serious adverse events caused by ciprofloxacin in pigmented tissues. It is known that some fluoroquinolones bind well to melanin rich tissues, but the relation between their affinity to melanin and the skin or eye toxicity is not well documented. The aim of this study was to examine whether ciprofloxacin binds to melanin, and how this interaction affects the proliferation and melanization in melanocytes. We have demonstrated that complexes which ciprofloxacin forms with melanin possess at least two classes of independent binding sites. Their association constants are K1 ~ 105 M− 1 and K2 ~ 102 M− 1, respectively. Ciprofloxacin has induced evident concentration-dependent loss in melanocytes viability. The value of ED50 was found to be ~ 0.5 mM. It has also been shown that ciprofloxacin reduces melanin content, and decreases tyrosinase activity in human skin melanocytes. The ability of ciprofloxacin to interact with melanin and its inhibitory effect on melanization in melanocytes in vitro may explain a potential role of melanin in the mechanisms of ciprofloxacin toxic effects in vivo.

The demonstrated effect of ciprofloxacin on cell viability and melanization process in pigmented cells in vitro can imply the role of melanocytes and melanin in vivo in the mechanisms of undesirable side effects of this drug on pigmented tissues.81