vasculitis
Amoxicillin Adverse Reactions
Hypersensitivity reactions are among the most frequent side effects of the penicillins. These reactions may include rash (unspecified), serum sickness, hypersensitivity-related rashes, and/or anaphylactoid reactions including anaphylactic shock. Hypersensitivity-related rashes include bullous rash, erythema multiforme, exfoliative dermatitis, maculopapular rash with erythema, toxic epidermal necrolysis, Stevens-Johnson syndrome, hypersensitivity vasculitis, and urticaria. These rashes occur more frequently with the aminopenicillins than with the other penicillins. The incidence of rash secondary to amoxicillin seems to be higher in patients with a history of allergy or atopy, or in those patients with viral illnesses such as mononucleosis, or in patients with lymphocytic leukemia. Interstitial nephritis or nephrotic syndrome resulting in oliguric renal failure has been reported in a small number of patients. Crystalluria has also been reported.
Hematologic effects seen with aminopenicillins include eosinophilia and hemolysis and are associated with hypersensitivity reactions. Other reactions seen include anemia (including hemolytic anemia), thrombocytopenia, thrombocytopenic purpura, neutropenia, agranulocytosis, and leukopenia. These adverse hematologic effects are generally reversible after discontinuation of the aminopenicillin. Platelet dysfunction, prolonged bleeding time, and prolongation of APTT have been reported in patients receiving amoxicillin and ampicillin.
Amoxicillin has been associated with acute generalized exanthematous pustulosis (AGEP). The nonfollicular, pustular, erythematous rash starts suddenly, is associated with fever above 38 degrees C, and is distinct from pustular psoriasis, although biopsy results in each reveal spongiform subcorneal pustules. Drugs are the main cause of AGEP. A period of 2 - 3 weeks after an inciting drug exposure appears necessary for a first episode of AGEP. Unintentional reexposure may cause a second episode within 2 days. Clinical presentation is diverse with cutaneous lesions beyond erythema and pustules present in half of the cases. For example, bullous lesions, edema, purpura, pruritus, and mucosal erosions are possible. The mean duration of the pustules is 9.7 days followed by an annular desquamation, as long as the causative drug or factor is discontinued. The physiopathological mechanisms of AGEP have not been determined but the pathological criteria of edema, leukocytoclastic vasculitis, eosinophil exocytosis, and keratinocyte focal necrosis are distinctive. Pustule confluence or very small pustules may lead a clinician to make an incorrect diagnosis of TEN, of drug-induced erythroderma, or of staphylococcal scalded skin syndrome.
Nausea/vomiting, anorexia, diarrhea, gastritis, and abdominal pain are commonly reported gastrointestinal side effects from antibiotics; however, amoxicillin, due to higher oral bioavailability, should cause less diarrhea than ampicillin. Amoxicillin has been rarely reported to cause esophagitis in some patients. Amoxicillin may be irritating to the esophagus if transit of the pill through the esophagus is delayed. Odynophagia, mid-chest pain, and dysphagia may be symptoms of esophagitis. Antibiotic-associated colitis, also known as pseudomembranous colitis can occur during use of or following discontinuance of amoxicillin, but this effect is rare.
Superinfection can occur with amoxicillin therapy. Prolonged or repeated therapy in particular can result in overgrowth by non susceptible bacteria or fungi. Candidiasis may occur as oral candidiasis (rare) or vaginal candidiasis.
More common central nervous system reactions include headache. On rare occasions, agitation or motor hyperactivity, confusion, dizziness, insomnia, or other behavioral changes have been reported. Seizures have been reported when large doses of penicillins were administered to patients with renal impairment. Appropriate dosage adjustments should be observed in these patients.
Hepatic dysfunction is a very rare side effect but has been reported as cholestatic jaundice, cholestasis, or acute cytolytic hepatitis. Other reported side effects of amoxicillin include elevated hepatic enzymes (e.g., moderate rises in AST and/or ALT).
Tooth discoloration (brown, yellow, or gray staining) has been rarely reported with amoxicillin therapy. The majority of reports have been in children. In most cases, discoloration was reduced or eliminated by brushing or dental cleaning. A follow-up study accessing fluoride intake and amoxicillin use reported a possible link to amoxicillin-associated dental fluorosis affecting permanent teeth. After adjusting for fluoride intake and otitis media, the study noted a significant increase in the risk of fluorosis with amoxicillin therapy.
[ Last revised: 10/19/2005 2:09:00 PM ]
References
. Nicholls PJ. Neurotoxicity of penicillins. J Antimicrob Chemother 1980;6:161 - 72.
. Beylot C, Doutre M, Beylot-Barry M. Acute generalized exanthematous pustulosis. Semin Cutan Med Surg 1996;15:244 - 9.
. Hong L, Levy SM, Warren JJ, et al. Association of amoxicillin use during early childhood with developmental tooth enamel defects. Arch Pediatr Adolesc Med 2005;159:943 - 948.
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