Amoxicillin (Amoxil), either alone or in combination as amoxicillin/clavulanic acid (Augmentin), is used to treat a wide variety of infections. Amoxicillin belongs to the penicillin class of antibiotics. It comes in several forms, including tablets, capsules and liquid suspensions. Although amoxicillin is generally safe, potential side effects include stomach upset, diarrhea, yeast infections and a variety of less common conditions, some of which can be serious.
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Common Side Effects
The most common side effects of amoxicillin are nausea, vomiting, stomach pain and diarrhea. These are typically short-lived and resolve once you stop taking the antibiotic. Although amoxicillin destroys infection-causing bacteria, it will also destroy the good bacteria that naturally reside in the body. This can lead to an overgrowth of yeast, which may not only produce diarrhea but also cause yeast infections, especially in the mouth and vagina. Oral thrush is a yeast infection that appears as a white coating in the mouth. A study in the January 2015 issue of the "Canadian Medical Association Journal" reported that yeast infections are about 7 times more common in people taking amoxicillin compared to people not taking any antibiotic.
Allergic and Hypersensitivity Reactions
Allergic reactions can happen with any antibiotic. Reactions may be minor, such as mild rashes or hives. Occasionally, amoxicillin can cause an anaphylactic reaction. This is a severe allergic reaction that includes a rapid onset of hives, swelling, difficulty breathing and dizziness or lightheadedness. It requires immediate medical attention. Other rare types of allergic or hypersensitivity reactions include Stevens-Johnson syndrome and serum sickness. Stevens-Johnson syndrome is characterized by fever, flu-like symptoms and a severe, peeling rash. Serum sickness occurs when the antibiotic causes an immune reaction in the body, leading to generalized symptoms such as fever, rash or joint pain. Discontinue amoxicillin and seek medical treatment immediately if you think you are having an allergic or hypersensitivity reaction.
Other Rare Side Effects
Other much less common side effects include disorders of the blood, such as low white blood cell counts, low platelet counts or anemia -- low red blood cell counts. Problems with the liver and behavior changes may also occur, but these are also rare. Occasionally, amoxicillin may cause pseudomembranous colitis, a severe form of diarrhea that usually requires hospitalization.
Special Considerations and Warnings
Amoxicillin is safe for children and breast-feeding mothers, but women should tell their doctor if they are pregnant prior to taking any antibiotic. Amoxicillin is only prescribed for bacterial infections and it will not help if you have a viral infection like the common cold. Tell your doctor about all your allergies and medications. Amoxicillin can interact with several other drugs. It can, for example, reduce the effectiveness of birth control pills and increase the risk of bleeding from blood thinners like warfarin. You should not receive amoxicillin if you are allergic to any other penicillin drugs or any type of cephalosporin antibiotics. Seek immediate medical attention if you have a rash, swelling, difficulty breathing or lightheadedness.
- DailyMed: Amoxicillin
- ToxNet LactMed: Amoxicillin
- Canadian Medical Association Journal: Common Harms From Amoxicillin: A Systematic Review and Meta-analysis of Randomized Placebo-Controlled Trials for any Indication
- Nelson Textbook of Pediatrics, 18th Edition; Robert Kliegman et al.