A review recently published in the International Journal of Dermatology has shown that six natural supplements commonly recommended in dermatology (nicotinic acid [nicotinamide], polypodium leucotomos [heliocare], turmeric, horse chestnut seed extract, zinc, and N-acetylcysteine) have notable drug interactions.
For nicotinic acid, zinc, horse chestnut, and N-acetylcysteine, IBM Micromedex generated 11, 23, one, and two results, respectively. Further review of literature from PubMed identified two drug interactions with polypodium leucotomos, two with turmeric, and two more with zinc. Notable interactions included an increased risk of myopathy and rhabdomyolysis when nicotinic acid is taken by patients using statins, an increased risk of bleeding associated with horse chestnut seed, especially when used in combination with warfarin, and reduced plasma concentration in many drugs when taken with zinc.
N-acetylcysteine may interfere with concentrations of other medications used in the psychiatric setting, and polypodium leucotomos and turmeric may interfere with the CYP metabolic pathway, which may affect drugs metabolized by this pathway.