Penicillin treats different illnesses by preventing the spread of bacteria, according to MedicineNet. It treats such ailments as middle ear infections, laryngitis, bronchitis and urinary tract infections.
MedicineNet mentions that penicillin is a mold that hampers bacterial growth. It was discovered in 1928 and was an effective medicine for soldiers during World War II. Since then, penicillin has been synthesized for intestinal absorption and to fight more infections. Wikipedia mentions extended-spectrum penicillin, which is the most effective type of penicillin for treating a broader range of diseases.
MedicineNet adds that penicillin does not kill bacteria but prevents them from dividing and forming protective cell walls. Since bacteria cannot survive without cell walls, they usually die from being unprotected. Penicillin can be taken in the form of injections, chewable tablets or capsules, and the dosage varies on the patient. Penicillin levels in the blood increase with the aid of probenecid, which slows down the kidney's ability to expel penicillin. It is also used so a lower amount of penicillin results in high blood levels.
MedicineNet claims that penicillin is considered safe to use for pregnant women, but it can get into the mother's nursing milk, which may result in allergic reactions or diarrhea in infants. However, it is used to treat infections in newborns. General side effects of penicillin include itching, vomiting, insomnia and rashes.