Reassure him that common ADD medications, like methylphenidate (Ritalin), have been around since the 1930s. The side effects are well known and, according to many doctors, after years of research, less harmful than those of aspirin.
Remind your husband that there is a side effect to not taking medication — unrelieved ADD symptoms that interfere with your life. Help educate your husband about your condition by buying him a copy of Driven to Distraction, by Ned Hallowell. You should also have him meet with your doctor, who can talk with him about living with untreated ADHD.