Hello and Welcome to ‘Ask A Doctor’ service. I have reviewed your query and here is my advice. One adverse effect of Atorvstatin is myositis , that is inflammation of the muscles. Erythromycin can potentially increase this side effect, i.e, slight more chances to cause myositis. However, its not very common, so you can start both.If you develop severe body ache then you should talk to your doctor. Your doctor will check for inflammation (this precaution need to be observed with Atorvastatin even if you do not take Erythromycin, but with it the risk is slightly increased). Otherwise these can be taken together. Hope I have answered your query. Let me know if I can assist you further.