Complexation of tetracyclines with metal ions in relation to photosensitization.

It has been shown by spectroscopy and by a Photosensitive Index method, involving measurements of interfacial tension, that Cu2+ and Ni2+ form 2:1 complexes with oxytetracycline and 1:1 complexes with demethylchlortetracycline. Fe2+, Zn2+, Mg2+ and Ca2+ form weaker 1:1 complexes with both drugs. The possibility is discussed of using metal ions to reduce photosensitization by tetracyclines in-vivo.