Greetings, and thank you for your question. Aspirin can lead to kidney damage if taken too long or at high doses. Lithium also has the possibility of causing renal damage, so the two together can work synergistically to harm the kidneys; kidney function should be monitored while on lithium, anyway, but especially when aspirin or medications like it are taken.
Ephedrine plus caffeine, or other stimulant medications, can lead to intravascular volume depletion, meaning you get more dehydrated. In persons taking lithium, this may cause the level of lithium to rise. If it rises enough, it may become toxic.
Hope this helps to get you started! Please let me know if you have other questions when you are online again.