As with other cephalosporins, bactericidal action of cefixime results from inhibition of cell-wall synthesis. Cefixime is highly stable in the presence of beta-lactamase enzymes. As a result, many organisms resistant to penicillins and some cephalosporins due to the presence of beta-lactamases, may be susceptible to cefixime. Cefixime has been shown to be active against most strains of the following organisms both in vitro and in clinical infections.
Gram-positive Organisms: Streptococcus pneumoniae
, Streptococcus pyogenes
Gram-negative Organisms: Haemophilus influenzae
(beta-lactamase positive and negative strains), Moraxella
(most of which are beta-lactamase positive), Escherichia coli
, Proteus mirabilis
, Neisseria gonorrhoeae
(including penicillinase- and non-penicillinase-producing strains).
Cefixime chewable tablets are bioequivalent to oral suspension.
Cefixime chewable tablets, given orally, is about 40%-50% absorbed whether administered with or without food; however time to maximal absorption is increased approximately 0.8 hours when administered with food. Cefixime chewable tablets produce average peak concentrations approximately 25%-50% higher than the tablets, when tested in normal adult volunteers. Two hundred mg dose of cefixime chewable tablets produce average peak concentrations of 3 mcg/mL (range 1 to 4.5 mcg/mL), when tested in normal adult volunteers. The area under the time versus concentration after curve is greater by approximately 10%-25% with the cefixime chewable tablets than with the tablet after doses of 100 to 400 mg, when tested in normal adult volunteers. This increased absorption should be taken into consideration if the cefixime chewable tablet is to be substituted for the tablet. Because of the lack of bioequivalence, tablets should not be substituted for cefixime chewable tablets in the treatment of otitis media. Cross-over studies of tablet versus chewable tablets have not been performed in children.
Peak serum concentrations occur between 2 and 5 hours following a single administration of 200 mg of chewable tablets.
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Approximately 50% of the absorbed dose is excreted unchanged in the urine in 24 hours. In animal studies, it was noted that cefixime is also excreted in the bile in excess of 10% of the administered dose. Serum protein binding is concentration independent with a bound fraction of approximately 65%. The serum half-life of cefixime in healthy subjects is independent of dosage form and averages 3-4 hours but may range up to 9 hours in some normal volunteers.
In subjects with half moderate impairment of renal function (20 to 40 mL/min creatinine clearance), the average serum half-life of cefixime is prolonged to 6.4 hours. In severe renal impairment (5 to 20 mL/min creatinine clearance), the half-life increased to an average of 11.5 hours. The drug is not cleared significantly from the blood by hemodialysis or peritoneal dialysis.