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Related to penicillins: Cephalosporins




Penicillins are medicines that kill bacteria or prevent their growth.


Penicillins are antibiotics (medicines used to treat infections caused by microorganisms). There are several types of penicillins, each used to treat different kinds of infections, such as skin infections, dental infections, ear infections, respiratory tract infections, urinary tract infections, gonorrhea, and other infections caused by bacteria. These drugs will not work for colds, flu, and other infections caused by viruses.


Examples of penicillins are penicillin V (Beepen-VK, Pen-Vee K, V-cillin K, Veetids) and amoxicillin (Amoxil, Polymox, Trimox, Wymox). Penicillins are sometimes combined with other ingredients called beta-lactamase inhibitors, which protect the penicillin from bacterial enzymes that may destroy it before it can do its work. The drug Augmentin, for example, contains a combination of amoxicillin and a betalactamase inhibitor, clavulanic acid.
Penicillins are available only with a physician's prescription. They are sold in capsule, tablet (regular and chewable), liquid, and injectable forms.

Recommended dosage

The recommended dosage depends on the type of penicillin, the strength of the medicine, and the medical problem for which it is being taken. Check with the physician who prescribed the drug or the pharmacist who filled the prescription for the correct dosage.
Always take penicillins exactly as directed. Never take larger, smaller, more frequent, or less frequent doses. To make sure the infection clears up completely, take the medicine for as long as it has been prescribed. Do not stop taking the drug just because symptoms begin to improve. This is important with all types of infections, but it is especially important with "strep" infections, which can lead to serious heart problems if they are not cleared up completely.
Take this medicine only for the infection for which it was prescribed. Different kinds of penicillins cannot be substituted for one another. Do not save some of the medicine to use on future infections. It may not be the right treatment for other kinds of infections, even if the symptoms are the same.
Penicillins work best when they are at constant levels in the blood. To help keep levels constant, take the medicine in doses spaced evenly through the day and night. Do not miss any doses.
Some penicillins, notably penicillin V, should be taken on an empty stomach, but others may be taken with food. Check package directions or ask the physician or pharmacist for instructions on how to take the medicine.


Symptoms should begin to improve within a few days of beginning to take this medicine. If they do not, or if they get worse, check with the physician who prescribed the medicine.
Penicillins may cause diarrhea. Certain diarrhea medicines may make the problem worse. Check with a physician before using any diarrhea medicine to treat diarrhea caused by taking penicillin. If diarrhea is severe, check with a physician as soon as possible. This could be a sign of a serious side effect.
Penicillins may change the results of some medical tests. Before having medical tests, patients who are taking penicillin should be sure to let the physician in charge know that they are taking this medicine.

Special conditions

People with certain medical conditions or who are taking certain other medicines can have problems if they take penicillins. Before taking these drugs, be sure to let the physician know about any of these conditions:
ALLERGIES. People who have hay fever, asthma, eczema, or other general allergies (or who have had such allergies in the past) may be more likely to have severe reactions to penicillins. They should be sure their health care provider knows about their allergies.
Anyone who has had unusual reactions to penicillins or cephalosporins in the past should let his or her physician know before taking the drugs again. The physician should also be told about any allergies to foods, dyes, preservatives, or other substances.
LOW-SODIUM DIET. Some penicillin medicines contain large enough amounts of sodium to cause problems for people on low-sodium diets. Anyone on such a diet should make sure that the physician treating the infection knows about the special diet.
DIABETES. Penicillins may cause false positive results on urine sugar tests for diabetes. People with diabetes should check with their physicians to see if they need to change their diet or the doses of their diabetes medicine.
PHENYLKETONURIA. Some formulations of Augmentin contain phenylalanine. People with phenylketonuria (PKU) should consult a physician before taking this medicine.
OTHER MEDICAL CONDITIONS. Before using penicillins, people with any of these medical problems should make sure their physicians are aware of their conditions:
  • bleeding problems
  • congestive heart failure
  • cystic fibrosis
  • kidney disease
  • mononucleosis ("mono")
  • stomach or intestinal problems, especially ulcerative colitis
USE OF CERTAIN MEDICINES. Taking penicillins with certain other drugs may affect the way the drugs work or may increase the chance of side effects.

Side effects

The most common side effects are mild diarrhea, headache, vaginal itching and discharge, sore mouth or tongue, or white patches in the mouth or on the tongue. These problems usually go away as the body adjusts to the drug and do not require medical treatment unless they continue or they are bothersome.
More serious side effects are not common, but may occur. If any of the following side effects occur, get emergency medical help immediately:
  • breathing problems, such as shortness of breath or fast or irregular breathing
  • fever
  • sudden lightheadedness or faintness
  • joint pain
  • skin rash, hives, itching, or red, scaly skin
  • swelling or puffiness in the face
Other rare side effects may occur. Anyone who has unusual symptoms after taking penicillin should get in touch with his or her physician.


Birth control pills may not work properly when taken at the same time as penicillin. To prevent pregnancy, use additional methods of birth control while taking penicillin, such as latex condoms or spermicide.
Penicillins may interact with many other medicines. When this happens, the effects of one or both of the drugs may change or the risk of side effects may be greater. Anyone who takes penicillin should let the physician know all other medicines he or she is taking. Among the drugs that may interact with penicillins are:
  • Acetaminophen (Tylenol) and other medicines that relieve pain and inflammation
  • medicine for overactive thyroid
  • male hormones (androgens)
  • female hormones (estrogens)
  • other antibiotics
  • blood thinners
  • Disulfiram (Antabuse), used to treat alcohol abuse
  • antiseizure medicines such as Depakote and Depakene
  • blood pressure drugs such as Capoten, Monopril, and Lotensin

Key terms

Enzyme — A type of protein that brings about or speeds up chemical reactions.
Microorganism — An organism that is too small to be seen with the naked eye.
Mononucleosis — An infectious disease with symptoms that include severe fatigue, fever, sore throat, and swollen lymph nodes in the neck and armpits. Also called "mono."
The list above does not include every drug that may interact with penicillins. Be sure to check with a physician or pharmacist before combining penicillins with any other prescription or nonprescription (over-the-counter) medicine.
Gale Encyclopedia of Medicine. Copyright 2008 The Gale Group, Inc. All rights reserved.


An important group of antibiotic drugs. The original natural penicillin was derived from the mould Penicillium notatum but the extensive range of penicillins in use nowadays is produced synthetically. The original penicillins was penicillin G (Crystapen), which had to be given by injection. This was followed by the phenoxymethyl derivative, penicillin V, which could be taken by mouth. The semisynthetic penicillins followed from the discovery that 6-aminopenicillanic acid could be obtained from cultures of Penicillium chrysogenum . The penicillin molecule contains a beta-lactam ring and many organisms produce an enzyme, beta-lactamase, that can inactivate the drug by breaking this ring. Side chains are added to the basic molecule to try to frustrate the action of this enzyme. Penicillins act by interfering with the synthesis of the walls of bacteria.
Collins Dictionary of Medicine © Robert M. Youngson 2004, 2005

Patient discussion about penicillins

Q. is it possible to drink alcohol during taking penicillin antibiotic?

A. i know that it's probably bad to take antibiotics with alcohol but couldn't remember why. so i looked you question up until i found a Doctor's answer to it-

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References in periodicals archive ?
Penicillins can be separated into groups based on their antibacterial activity and how they are absorbed, distributed, metabolized, and excreted by the body.
The use of penicillins over many years for a wide variety of conditions should not stop us from continuing to identify the most appropriate dose which gives us the most effective outcomes.
The pharynx may be co-colonized by bacterial pathogens that can inactivate penicillins and make them ineffective against GABHS.
In fact, the risk that a patient with a history of penicillin allergy will experience a reaction to a first-generation cephalosporin is not more than 0.5%, to a second-generation cephalosporin, not more than 0.2%, and to a third-generation cephalosporin, practically nil.
We noticed a seemingly high prevalence of penicillin allergy among patients who were diagnosed with PTA in our ER.
Penicillin skin testing in patients with a history of penicillin allergy does not reliably predict allergy to a cephalosporin unless the side chain of the penicillin or ampicillin reagent is similar to the cephalosporin side chain being tested) The positive and negative predictive values of skin testing results for cephalosporins are not well established; if the haptens that cause cephalosporin allergy were known, cross-reactivity with penicillins could be assessed directly.
He has a penicillin allergy (rash on chest, back, and arms 25 years ago).
Among the earliest known clinical uses of penicillin was by Cecil George Paine, a pathologist at the Sheffield Royal Infirmary, who successfully used it in 1930 to treat gonococcal conjunctivitis in neonates.
Now, for the first time, experts at Newcastle University, whose study is published online today in Cell, have identified how lysozyme and penicillin could work in combination to cause recurrent infections.
The aim of this study was to compare the diagnostic value of two imunoglobulin E assays for penicillin in a group of patients with a history compatible with hypersensitivity reaction during penicillin treatment who exhibited positive skin testing and/or a drug provocation testing.
With routine performance of penicillin skin testing using standard methods in a consecutive series of inpatients with a self-reported history of penicillin allergy, roughly 80% were found to not in fact be allergic.

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