Unlikely but serious side effects of isorsobide mn are: more frequent or worsening chest pain, flushing, unusually slow or fast heartbeat, fainting. A serious allergic reaction to this drug is unlikely, but seeks immediate medical attention if it occurs. Symptoms of a serious allergic reaction include: rash, itching, swelling, severe dizziness, trouble breathing. If you notice other effects not listed above, contact your doctor or pharmacist immediately.