I had a friend who started taking Zantac for continual indigestion. A few days after starting to take them his heart beat became irregular, but it was okay of he exercised. He went to see his doctor who said he had an ectopic? heartbeat and sent him to a specialist. His ECG was abnormal and he was told to return in 3 days to have one of those 24 hour tape recorder ECG machines fitted. In the meanwhile he was also advised to stop taking Zantac and see if he returned to normal, which he did. After returning to the hospital he was again given an ECG which was normal and he said that within 24 hours of stopping the Zantac his symptoms had disappeared. Maybe this is giving some other pilots problems too.