Examples

How It Works

Penicillins are antibiotics that kill bacteria.

Why It Is Used

Doctors use penicillins to fight many infections, including pneumococcal pneumonia, meningococcal meningitis, and some strains of Haemophilus influenzae. Penicillins are the antibiotics of choice in fighting uncomplicated infections caused by Streptococcus pneumoniae, the most common cause of pneumonia when the cause is identified.¹

How Well It Works

In general, all antibiotics used have a high cure rate for pneumonia. Cure rates are greater than 80%, meaning at least 80 people out of 100 are cured.²

Penicillins kill some types of bacteria that cause pneumonia, but do not work against all types of bacteria.

In some cases, bacteria are resistant to penicillins, so another type of antibiotic is needed.

Penicillin may be more effective when it is used with another medicine such as clavulanate.

Side Effects

The main side effects of penicillin are:

• Skin rashes.
• Nausea.
• Discolored or sore tongue.
• Mild diarrhea and upset stomach, especially if you take the medicine on an empty stomach.

People who are allergic to penicillins may have a severe reaction. If they have had such a reaction to penicillins in the past, they should take another kind of antibiotic. Signs of severe allergic reaction include difficulty breathing and a tight throat.

See Drug Reference for a full list of side effects. (Drug Reference is not available in all systems.)

What To Think About

Penicillins cannot always kill bacteria (antibiotic resistance), in part because they are used too much. You can help prevent antibiotic resistance by taking all of your medicine as directed, even if you feel better after a few days. If you stop taking your medicine too soon, bacteria that are not killed in the first few days of treatment can grow stronger and become resistant to the antibiotic.

Complete the new medication information form (PDF)(What is a PDF document?) to help you understand this medication.

References

Citations

1. Simon HB (2006). Pneumonia and other pulmonary infections. In DC Dale, DD Federman, eds., ACP Medicine, section 7, chap. 20. New York: WebMD.
2. Loeb M (2008). Community-acquired pneumonia, search date June 2007. Online version of BMJ Clinical Evidence: http://www.clinicalevidence.com.