Side Effects Of Amoxicillin And How Often They Occur

Quicken asked

Can you tell me the possible side effects of amoxicillin and the likelihood of them happening?

Answer

Amoxicllin is a very popular and useful antibiotic that is a derivative of penicillin. Amoxicillin is in fact known as an "aminopenicillin" and is effective against many more strains of bacteria than penicillin is. Amoxicillin is used to treat many different types of infections including upper respiratory tract infections and urinary tract infections. While typically well tolerated, amoxicillin can cause side effects and unwanted adverse reactions. The most significant of these side effects is actually a type allergy known as a hypersensitivity reaction. We will discuss this and the other possible side effects below.

Hypersensitivity Reaction

Hypersensitivity reactions are the most common adverse reactions in patients taking penicillin type drugs. Hypersensitivity reactions occur in patients who have an allergy or sensitivity to the medication. It has been reported that as many as 5% of the general population have a sensitivity to penicillin drugs.

There doesn't seem to be one drug in the penicillin class that affects more patients than another. The most common symptoms of a hypersensitivity reaction are rash, fever, wheezing/trouble breathing and itching. The most serious hypersensitivity reactions that can occur are angioedema and anaphylaxis. Angioedema is the rapid swelling of the skin and anaphylaxis is a whole body allergic reaction that can be extremely serious. While both angioedema and anaphylaxis are not very common, patients who experience either must seek immediate medical attention. If a patient does experience any symptom of a hypersensitivity reaction, the medication should be stopped and the patient should contact their physician. It should be noted that if someone is allergic to one type of penicillin type drug, they should be considered to be allergic to all of the penicillin type drugs. For example, if a patient has a known sensitivity to penicillin, they should be not be given amoxicillin.

​Additional Side Effects

Gastrointestinal

Aside from hypersensitivity reactions, gastrointestinal side effects are the next most common for amoxicillin. Nausea, vomiting, diarrhea and abdominal pain may occur after taking the medication by mouth.

​Superinfection

The longer a patient is on an antibiotic therapy, the greater the chances of overgrowth of a bacteria or fungus that is not affected by the drug. A common example of this is with the bacteria clostridium difficile. This bacteria is a regular part of your digestive tract and is balanced out by all of the other bacteria that your gut contains. Clostridium difficile is not susceptible to the effects of amoxicillin and can overgrow/cause significant side effects when certain antibiotics are introduced that take care of the other bacteria in the gut. The overgrowth can cause significant cramping and diarrhea. A common preventative is to take probiotics while on antibiotic therapy. Probiotics helps balance out and maintain the bacteria in the GI tract.

In addition to the overgrowth of "bad bacteria", growth of fungus can occur. Women are particularly likely to get a fungal or yeast infection while taking antibiotics such as amoxicillin. Probiotics can again help prevent this.

Neurotoxicity

Neurotoxicity is not a common side effect of amoxicillin. Headaches, irritability, confusion, hallucinations and seizures are all reported side effects however. These have a low likelihood of happening and are typically associated with penicillin given by injection.​

Blood Effects

Very rarely, certain adverse reactions involving the blood can occur. Examples of this are anemia (a decrease in red blood cells and neutropenia (a decrease in neutrophils).

Tooth Effects

Tooth discoloration (color change to brown or yellow) has been reported extremely rarely. The vast majority of cases has been in children. In most cases, the discoloration was eliminated by continuous brushing and professional cleanings from a dentist.

Here is a chart listing how common each of the side effects are: