viral infection
Amoxicillin Contraindications and Precautions
Amoxicillin is a penicillin and should not be used in patients with a penicillin hypersensitivity. Amoxicillin should be used cautiously in patients with cephalosporin hypersensitivity or carbapenem hypersensitivity. These patients are more susceptible to hypersensitivity reactions during therapy with amoxicillin; the incidence of true cross-sensitivity has been estimated at roughly 3 - 5%. Patients with allergies or atopic conditions including asthma, eczema, hives, or hay fever may have a greater risk for hypersensitivity reactions to penicillins.
Amoxicillin should be used with caution in patients with renal impairment since the drug is eliminated via renal mechanisms. Amoxicillin dosage should be adjusted in those patients with CrCl <= 30 ml/min and in those patients with renal failure. Dosage adjustments are also recommended for patients receiving dialysis (see Dosage).
Penicillins should be used with caution in patients with a history of GI disease, especially colitis, because the adverse GI effects associated with penicillin therapy can exacerbate the condition.
Patients who develop diarrhea while taking or soon after discontinuing amoxicillin should be considered for differential diagnosis of antibiotic-associated pseudomembranous colitis. Antibiotic therapy can also result in overgrowth or secondary infection with non susceptible organisms, like Candida spp. Patients should be monitored closely during therapy.
Amoxicillin has been used to treat infections in infants <= 3 months of age, including neonates. However, dosages must be modified for these age groups compared to infants > 3 months of age because of incompletely developed renal function (see Dosage).
Based on manufacturer data, elderly patients (age > 65 years) do not respond differently to amoxicillin treatment than younger patients. However, a greater sensitivity to amoxicillin in elderly patients could not be ruled out. Amoxicillin is known to be substantially excreted via the kidney. Because elderly patients are more likely to have decreased renal function, the risk of adverse reactions to amoxicillin may be greater. Care should be taken in dose selection for elderly patients; renal function monitoring may be useful.
Amoxicillin is classified in FDA pregnancy category B. Animal data reveal no teratogenic effects, however, there are no adequate and well-controlled studies in pregnant women. While amoxicillin should be used with caution in pregnancy, penicillins are usually considered safe during pregnancy when clearly needed.
Amoxicillin is excreted in breast milk in small amounts. Penicillins may cause diarrhea (due to disruption of GI flora), candidiasis, and skin rash in breast-feeding infants. Unless the infant is allergic to penicillins, breast-feeding is generally safe during maternal penicillin therapy; the infant should be observed for potential effects. As with all drugs, the potential risk to the nursing infant should be considered versus the potential benefit in the mother.
Patients with phenylketonuria should be warned that the chewable tablets and the tablets for oral suspension (DisperMox™) contain phenylalanine. Amoxicillin chewable tablets contain phenylalanine in the amount of 1.82 mg per 200 mg tablet and 3.64 mg per 400 mg tablet. Each 200 mg DisperMox™ Tablet for oral suspension contains 5.6 mg phenylalanine and each 400 mg tablet contains 5.6 mg phenylalanine. The oral suspensions do not contain phenylalanine.
A false-positive reaction for glucose in the urine has been observed in patients receiving penicillins and using Benedict’s solution, Fehling’s solution, or Clinitest® tablets for urine glucose testing. However, this reaction has not been observed with Tes-tape® (glucose Enzymatic Test Strip, USP, Lilly) or Clinistix®. Patients with diabetes mellitus who test their urine for glucose should use glucose tests based on enzymatic glucose oxidase reactions while on amoxicillin treatment.
Amoxicillin should be used with caution in those patients with lymphatic leukemia, because these patients may be more likely to develop a drug rash. Patients with an active viral infection such as CMV, viral respiratory infection, and especially mononucleosis have a high incidence of reported rashes to the penicillins.
Antimicrobial agents used in high doses for short periods of time to treat gonorrhea may mask or delay the symptoms of incubating syphilis. All patients with gonorrhea should have a serologic test for syphilis at the time of diagnosis. Patients treated with amoxicillin should have a follow-up serologic test for syphilis 3 months after treatment for gonorrhea.
[ Last revised: 2/20/2006 2:22:00 PM ]
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