Cymbalta is not known to interact with caffeine. But too much caffeine can cause symptoms such as nausea, headache, and trouble sleeping. These are also possible side effects of Cymbalta ...

Cymbalta (duloxetine) can cause a range of side effects when you stop taking it, especially if you discontinue it abruptly. This is known as a withdrawal or antidepressant discontinuation syndrome ...

Due to the way Cymbalta works on your central nervous system, your body can become used to the drug. So if you suddenly stop taking it, you may start to experience uncomfortable side effects.