All drugs, regardless of whether they are illegal, prescription or over-the-counter (available without a prescription), change your body and can be potentially harmful. Some over-the-counter drugs can cause serious problems or even death if used incorrectly. The only safe way to take any over-the-counter medication is exactly as directed and for the specific problem for which it is intended.
The health risks of abusing OTC cough and cold remedies include: impaired judgement, nausea, loss of coordination, headache, vomiting, loss of consciousness, numbness, stomach pain, irregular heartbeat, seizures, panic attacks, cold flashes, dizziness, diarrhea, addiction, restlessness, insomnia, high blood pressure, coma, and death. Like any other drug, overdoes from over-the-counter medication can occur.
Get the facts. Read: DrugFacts: Prescription and Over the Counter Medications.