Has anyone experienced any negative side-effects from nizoral (ketoconazole)?

Certainly: All medications will have someone have a side effect that is less than desirable. It involves a lot of factors.....Ketooconazole should not be taken with erythromycin's and in some can cause liver problems. Most people do very well and it is safe enough to have the topical form over the counter. Oral is still a prescription. Talk to your prescribing doctor if you have concerns.