What is it?
Amoxicillin is an antibiotic used to fight certain bacterial infections. It is completely ineffective against some bacteria as well as all viruses and fungi.
It is in the in the family of antibiotics known as Penicillins. Penicillins are in the broader class of antibiotics known as Beta-Lactams.
There are two big types of antibiotics known as bacteriocidal and bacteriostatic. Bacteriocidal antibiotics actually kill existing bacteria. Bacteriostatic antibiotics don’t actually kill existing bacteria, but instead inhibit the ability of the bacteria to reproduce. Thus, as existing bacteria die off (from “old age” and from attacks by the body’s immune system) the infection comes under control because new bacteria aren’t being produced to replace the dying ones. Though some antibiotics show both bacteriocidal and bacteriostatic activity, most antibiotics do one or the other. Penicillins (including amoxicillin) are bacteriocidal.
Penicillins kills susceptible bacteria by interfering with the way the bacteria makes it’s cell wall. Without a normal cell wall, the bacteria dies.
Some bacteria produce an enzyme known as Beta-Lactamase or Penicillinase which will inactivate and destroy penicillins. These bacteria are therefore very resistant to penicillins (as well as other Beta-Lactam antibiotics).
Sometimes other agents are added to the antibiotic to counteract this bacterial enzyme. A Common agent combined with Amoxicillin for this purpose is clavulonic acid. A common form of this is the brand name antibiotic Augmentin. In veterinary medicine there is a similar combination product known as Clavamox.
Amoxicillin tends to have much better absorption with oral dosing than most other Penicillins, and it is therefore commonly used in the outpatient setting.
Amoxicillin is not under any patent, and therefore it is available under many brand names and dosage forms. It is available as tablets, capsules, liquid suspensions etc.
Some common brand names in the united states include Amoxil and Trimox.
What is the normal dose?
There is a fairly wide dosage range in both adults and children, depending on the particular infection being treated.
Common adult doses might be anywhere from 250mg three times a day, to 2grams 2 times a a day.
In children it is frequently dosed according to the weight of the child. This is also the case in veterinary medicine.
What are some common side effects?
Like all medications, amoxicillin can have side effects. Probably the most common and most concerning side effects involve allergic reactions, which are fairly common with Penicillins. Patients may develop allergy symptoms ranging from mild rash and itch to full blown anaphylaxis (which is a severe and potentially fatal allergic reaction.).
Amoxicillin may also cause non-allergy related side effects including nausea, vomiting, diarrhea, mild rash or itch, black-hairy-tongue, elevations of liver enzymes, other blood disorders such as anemias or elevation of certain blood cells, seizures, and rarely liver or kidney damage.
Are there any interactions with other medicines?
Yes, there are potential interactions with lots of medicines.
In particular, amoxicillin should not be given with typhoid vaccination as it may inactivate the vaccine.
The medications Chloroquin and Exanatide may decrease the effect of Penicillins.
Amoxicillin may increase the concentration and/or effect of Methotrexate and Warfarin, and may decrease the effect of many oral contraceptive medications (so if you are a sexually active woman who doesn’t want to get pregnant and are prescribed amoxicillin, you should consider a course of abstinence or take other precautions against pregnancy).
In addition to these, there are many other medications that may have similar interactions. Therefore you should discuss any medications you are taking with your doctor and/or pharmacist prior to taking amoxicillin.
Are there any contraindications to taking Amoxicillin?
Yes. Amoxicillin should not be given to anyone with a history of allergy to Penicillins. It should be used with caution in anyone with a history of allergy to any cephalosporins (as they are also Beta-Lactam antibiotics and sometimes allergic cross-reactions can occur).
It should typically not be given to anyone with mononucleosis and should be used only with caution in anyone with Epstein Barr Virus or Cytomegalovirus. Also, caution should be used in any patient with decreased kidney or liver function or any PKU deficiency.
If you have, or thank you have any of these conditions, you should discuss them with your doctor or pharmacist before taking Amoxicillin.
Amoxicillin is generally considered safe in pregnant and nursing women, but obviously this should be discussed with your own personal physician if you are pregnant, think you might be pregnant, or are trying to become pregnant, or if you are nursing or planning to nurse a child.
