The antibiotic nafcillin is a member of the penicillin family that is prescribed to treat bacterial infections. Nafcillin is commonly used for infections stemming from staphylococcus, or staph, bacteria. Patients with pneumonia, meningitis or infections of the urinary tract, skin, blood or heart valves also are often prescribed nafcillin. The drug is usually injected into the body or administered through an intravenous drip, though it is also available as an oral medication in capsule or tablet form.
Like the similar oxacillin, nafcillin is considered a beta-lactam antibiotic, which works to restrict the growth of bacteria by inactivating enzymes in the bacterial cell membrane. Beta-lactam antibiotics are the most widely prescribed type of antibiotics. As such, they rank among the most widely used drugs of any type.
Nafcillin is injected into a large muscle, such as the hip or buttock, when the doctor has prescribed an intramuscular infusion of the drug. It is typically injected into a vein every four to six hours, according to the physician's instructions, when an intravenous infusion has been prescribed. When it is administered through an intravenous drip, the drug is added to a fluid that drips through a needle or catheter into a vein for 30 to 60 minutes, four to six times a day. As with all antibiotics, it is most effective when the amount of medication in the body is maintained at a constant level.
Patients who are taking nafcillin in capsule or tablet form are told to take it with a full 8 ounces (237 ml) of water on an empty stomach. Doctors should instruct their patients to avoid drinking alcohol while taking nafcillin to reduce the risk of stomach irritation. Patients should take the medication as instructed by their doctor, being sure to take all of it. Symptoms of the infection often clear up on the surface before the infection is fully treated, leading some patients to stop taking the medicine too soon and later suffer a harder-to-treat recurrence of the infection.
Before taking nafcillin, patients should inform their physician if they have asthma, kidney disease, liver disease or allergies to penicillin. Nafcillin is not effective in treating viruses, and it should not be prescribed for colds and flu. Women who are breastfeeding should talk to their doctor before taking nafcillin, because it can pass into breast milk and may harm a nursing baby. Possible side effects include diarrhea, headaches, nausea, vomiting, mouth sores and swelling or irritation at the site of the injection.