Toxicity is the major issue in deciding whether to switch a drug from prescription to OTC status. Because almost any drug, if misused, can have some adverse side effect, one way to evaluate possible harm in switching is to consider the drug's overall margin of safety. The process of switching some antihistamines to OTC status can serve as an example of the procedure. Antihistamines are used to relieve symptoms of hay fever and other upper respiratory allergies. They may cause drowsiness, however, presenting a hazard if taken in circumstances where alertness is important.
Antihistamines also can be dangerous to patients with glaucoma, an enlarged prostate, or asthma.
The panel also recommended that the label warn patients not to take these products except with the advice and supervision of a physician if they have glaucoma, asthma, or difficulty urinating because of an enlarged prostate. Another consideration in deciding whether or not a drug should be available without prescription is whether the condition being treated can be self-diagnosed. Inability to self-diagnose a condition, however, does not automatically preclude OTC status for products intended to treat its symptoms. Most OTC drugs are labeled for the treatment of symptoms, such as sinus congestion, headache, pain, upset stomach, and itching. Consumers can readily recognize these symptoms and select an appropriate product to gain relief, but they may not know what underlying condition is causing the pain, cough or itch they are self-medicating.