According to MedlinePlus, ampicillin is a penicillin-like antibiotic that treats a variety of bacterial infections, including ear, skin and urinary tract infections, pneumonia and bronchitis. Drugs.com explains that ampicillin works by interfering with cell wall formation in bacteria. The cell walls of the bacteria become weak and rupture, causing the bacteria to die.
When taking ampicillin, Drugs.com states that it is important to take the full course of treatment to ensure that the infection clears completely. Failure to do this can lead to the infection returning or the bacteria becoming less sensitive to the antibiotic, making the infection more difficult to treat in the future. The most common side effects of ampicillin are inflammation and redness of the tongue, mouth or throat irritation, mild diarrhea, nausea, vomiting or another infection. Signs of severe reaction that warrant immediate medical attention include rash, hives, difficulty breathing, bloody stools, stomach pain, or swelling of the face, tongue or lips.
Drugs.com reveals that ampicillin is contraindicated in some people, including those who are taking a tetracycline antibiotic, those who have mononucleosis, or those who have received or plan to receive live oral typhoid vaccine. Other medications, vitamins and herbal supplements may interact with ampicillin by decreasing its effectiveness or increasing the risk of side effects.