If your friend was cited for driving under the influence (DUI) while in your car then likely it will not affect your car insurance rates. He or she should have received the citation written out to them in their name so that the DUI will go on their record and not cause you any problems.

However if the person was in an accident with your car during this time then the resulting claims would go on your claims record and thus could affect your insurance premiums. Insurance typically follows a car first and driver second meaning that if your friend was driving drunk in your car then it would be your insurance policy that would be gone to primarily and the friend's insurance would be secondary or excess if your limits were exceeded.

Also as owner of the car you have vicarious liability normally for those that you allow to drive it so if all insurance limits were exceeded then in most states you and the driver may be held responsible for the damages he or she caused while operating your vehicle.