Melatonin partially eliminates the AIA/DDC-induced decrease in the activity of the gluconeogenic enzymes PEPCK and G6Pase. Melatonin favors a glucose-mediated down-regulating effect on AIA/DDC-induced ALA-S. Melatonin reduces AIA/DDC-increases in lipid peroxidation. Melatonin partially reverts the AIA/DDC-induced increase in ALA and PBG levels. The results obtained suggest the hypothetical use of Mel as co-treatment for acute porphyria.