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Cephalosporin offers extended spectrum of activity
Already a best-seller in Japan, Omnicef (cefdinir) was recently given the official nod to enter U.S. shores and take its rightful place as the tenth third-generation cephalosporin.
Manufactured by Warner-Lambert, the extended-spectrum, semisynthetic oral cephalosporin--approved for both adult and pediatric use--carries the following indications:
*Community-acquired pneumonia in adults
*Acute exacerbation of chronic bronchitis in adults
*Acute bacterial sinusitis in adults and children
*Pharyngitis and tonsillitis caused by Streptococcus pyogenes in adults and children
*Acute bacterial otitis media in children
*Uncomplicated skin and skin structure infections in adults and children
So which bugs fall prey to the new antibiotic? Of the gram-negative organisms, Haemophilus influenzae, H. parainfluenzae, and Moraxella catarrhalis have shown to be susceptible to cefdinir--including beta-lactamase-producing strains of those organisms. The drug's gram-positive coverage encompasses S. pyogenes, Staphylococcus aureus--including beta-lactamase-producing strains and excluding methicillin-resistant staphylococci--and penicillin-susceptible S. pneumoniae.
Unfortunately, penicillin-susceptible S. pneumoniae is becoming more of a rarity. Sujata Bhavnani, Pharm.D., Millard Fillmore Hospital, Buffalo, N.Y., cautioned that the bug is increasingly developing intermediate- and high-level resistance to penicillin and other drugs, including macrolides, chloramphenicol, and sulfonamides. Bhavnani was speaking at the ASHP's 32nd annual Midyear Clinical Meeting in Atlanta last month.
Jeff Kuper, Pharm.D., clinical assistant professor at Rutgers' College of Pharmacy, noted that last-resort vancomycin is usually the only option left for multidrug-resistant S. pneumoniae. This gradual decline of effective antibiotic options is alarming since S. pneumoniae is responsible for 3,000 cases of meningitis, 50,000 cases of bacteremia, 500,000 cases of pneumonia, and over seven million cases of otitis media yearly, according to Bhavnani.
What niche in therapy cefdinir will squeeze into has yet to be determined. The new cephalosporin will be competing with second- and other third-generation oral cephalosporins. Kuper noted that, typically, third-generation cephalosporins are reserved until other, less-expensive antibiotics fail in upper respiratory tract infections caused by S. pneumoniae. In cases where S. pneumoniae is not yet verified as the pathogen, a third-generation cephalosporin is employed as a first line of defense, since the class provides coverage against other respiratory tract-loving bugs, such as Haemophilus and Moraxella. If at that point a culture indicates that the infection is caused by S. pneumoniae and susceptibility testing suggests that the organism is sensitive to penicillin, the patient is switched.
How is the newest antibiotic tolerated? Generally well, according to results of clinical trials evaluating over 13,000 patients over a four-year period. Most common adverse effects occurring from cefdinir capsules in adults included diarrhea, vaginal moniliasis, nausea, headache, abdominal pain, and vaginitis. Discontinuations were usually due to diarrhea or nausea and, rarely, rash.
As with nearly all antibacterial agents, pseudomembranous colitis has been reported with cefdinir and may range in severity from mild to life-threatening. Diagnosis of the condition should be considered in treated patients who present with diarrhea.
Magnesium- or aluminum-containing antacids and iron supplements are known to interfere with absorption of cefdinir; therefore, the antibiotic should be taken at least two hours before or after those products. Food has not been shown to significantly affect the absorption of cefdinir.
Omnicef is available as 300-mg capsules and as an oral suspension containing 125 mg of cefdinir per 5 ml when reconstituted. The adult dosing recommendations for most infections is 600 mg given as either two capsules once daily or one capsule b.i.d. For pediatric patients, a dose of 14 mg/kg is administered once daily or divided into a b.i.d. regimen.