My wife has been using a compound containing 2% Lidocaine as one of the components for neck pain. Most recently she has experienced a rash, apparently in reaction to the compound. A doctor suggested trying a Lidocaine ointment with 5%, instead of the compound. She is taking medication for heart arrythmia and has a pacemaker. Is there any greater risk involved with this percentage of Lidocaine? Months ago she used a Lidocaine patch on her back while recovering from small spinal fractures without adverse effects.