Amoxicillin Side Effects

Amoxicillin

Amoxicillin Side Effects:  Brand names Amoxil, available in 250 mg., 500 mg, 850 mg capaules, 200, 400 and 250 mg chewable tablets, and 125 mg/ 5 ml, 200 mg/ 5 ml, 250 mg/ 5 ml and 400 mg/ 5 ml elixir.  Amoxicillin is in the penicillin class of medications, and was an early follow on drug to ampicillin with the benefit of better absorption from the gut when taken with food.  Amoxicillin remains a mainstay in the treatment of common respiratory infections despite increasing antibiotic resistance.  Most patients with allergy to other penicillins will also have this as an amoxicillin side effect, and like most antibiotics amoxicillin has diarrhea and risk of pseudomembranous colitis as possible side effects.

Common Amoxicillin Side Effects: The most common amoxicillin side effects are diarrhea and oral or vaginal candidiasis.  Other common gastrointestinal amoxicillin side effects include nausea and vomiting.  Urticaria is fairly common as an amoxicillin allergic rash, and eosinophilia, black hariy tongue and elevation of liver transaminases are also fairly common amoxicillin side effects.

Serious Amoxicillin Side Effects:   Allergic reactions to amoxicillin can be severe, incluging anaphylaxis, hypersensitivity, serum sickness-like reactions, Stevens-Johnson syndrome, toxic epidermal necrolysis, exfoliative dermatitis as well as the less serious rashes.  Serious hematologic amoxicillin side effects can include agranulocytosis, thrombotytopenia, leucopenia and anemia.  Both liver and kidney problems can occur as hepatotoxicity and interstitial nephritis.  Seizures are reported rarely.  As with most other antibiotics superinfection is a potential amoxicillin side effect.  Clostridium difficile infection causing diarrhea is an increasingly common serious problem with many antibiotics.  For more details and a complete list of potential amoxicillin side effects see the manufacturer’s prescriber details.

Cautions and Drug Interactions: Amoxicillin is nearly exclusively excreted unchanged in the urine, and so has no hepatic metabolism interactions with other drugs that use the liver for metabolism.  Warfarin may be the exception, but even this is usually minimal and alteration of warfarin anticoagulation effect is more likely due to alteration of the gut microflora than to alteration with hepatic metabolism. Among the most common issues with amoxicillin is the higher chance of pregnancy in oral contraceptive users who take amoxicillin.  Unplanned pregnancy due to this reduced contraceptive effectiveness is well documented, and back-up barrier contraception is recommended for birth control pill users who take amoxicillin.  In patients with infectious mono a rash is extremely common, and amoxicillin is best avoided in these patients.  Amoxicillin is contraindicated in patients who have recently received live BCG inoculation and oral typhoid vaccine.  The list of drugs where caution is advised is available from the manufacturer in the prescribing guidelines, but includes allopurinol, bupropion, tramadol, and the class of drugs known as proton pump inhibitors including omeprazole and others.

Unusual Amoxicillin Side Effects:  The extremely common rash in patients with infectious mononucleosis is quite unusual.  It is so common that in a patient with a severe sore throat that develops a reddish rash on amoxicillin mono should be considered.

Pregnancy and Lactation:  Amoxicillin is pregnancy category B and is felt to be safe for use in lactating women.