Neutropenia is a type of blood disorder that is caused by a decrease in the number of neutrophils, which are a type of white blood cell. Penicillin is an antibiotic drug that is commonly used to treat bacterial infections. While penicillin is generally a safe medication, it can cause some side effects, including neutropenia. The type of penicillin that is most commonly associated with causing neutropenia is ampicillin. Ampicillin is a semi-synthetic penicillin that is used to treat a wide variety of bacterial infections. It is important to note that not all people who take ampicillin will develop neutropenia, but it is a possible side effect. If you are taking ampicillin and experience symptoms such as fever, chills, or a sore throat, it is important to contact your doctor right away, as these could be signs of an infection. Your doctor may order a blood test to determine if you have developed neutropenia.