Newer fluoroquinolones offer better broad-spectrum coverage

A retrospective analysis showed a four-fold decrease in cases of endophthalmitis when a switch was made from third-generation to fourth-generation drugs, according to Michael Jensen, RPh, MS, clinical associate professor of pharmacy practice, College of Pharmacy, University of Utah, and clinical pharmacy specialist in ophthalmology, John A. Moran Eye Center, Salt Lake City.

"While most patients experience an uneventful postoperative course following cataract surgery, endophthalmitis may still occur despite the use of antibiotics administered preoperatively and postoperatively," said Jensen. "Previous published reports indicated that the rate of endophthalmitis was approximately 0.1%; however, more recent reports have suggested that the rate of endophthalmitis may be higher than previously thought."

With this in mind, he and colleague Richard G. Fiscella, RPh, who is affiliated with the Department of Pharmacy Practice, University of Illinois, Chicago, used an infectious events database to review the rate of occurrence of endophthalmitis associated with the use of postoperative topical quinolones in patients who underwent phacoemulsification. They wanted to determine the differences in the rates of endophthalmitis between the administration of the third-generation and the fourth-generation fluoroquinolones. The period of the study was from January 1997 to February 2005.

Jensen developed an infectious events collection system, which tracked the occurrence of nosocomial endophthalmitis after cataract surgery. For each case reported, the following information was collected: patient name, medical record number, date of presentation of infection, type of surgery, date and location of initial surgery, and medical and surgical interventions undertaken. The reports of each case were entered into the nosocomial database.

The investigators reported that from April 1, 1997, to March 1, 2001, a total of 9,079 cataract surgeries were performed in which ciprofloxacin 0.3% (Ciloxan, Alcon Laboratories) was used in 4,538 cases and ofloxacin 0.3% (Ocuflox, Allergan) was used in 4,541 cases. During this time, 26 cases of endophthalmitis developed, for an incidence of 2.86 per 1,000 cases-22 cases in patients who had received ciprofloxacin, and four in patients who had received ofloxacin.

This development resulted in the exclusive use of ofloxacin from March 1, 2001, to June 30, 2002. Subsequent to this period, an additional 3,000 cataract surgeries were performed, and only one case of endophthalmitis developed postoperatively, for an incidence of 0.3 cases per 1,000 surgeries.

Ofloxacin continued to be used exclusively until August 30, 2003. After another 4,651 cataract surgeries had been performed, the rate of development of endophthalmitis rose to 1.29 per 1,000 cases, according to the investigators.

Fourth-generation drugs

"Due to a four-fold increase in endophthalmitis and the advent of fourth-generation fluoroquinolones, we decided to begin use of gatifloxacin 0.3% (Zymar, Allergan) and moxifloxacin (Vigamox, Alcon Laboratories) for an 18-month period of evaluation," Jensen explained.

Between Sept. 1, 2003, and Feb. 28, 2005, each drug was alternated exclusively every other month; moxifloxacin was used in 2,563 cases and gatifloxacin used in 2,765 cases of cataract extraction. The results showed that both drugs had similar rates of clinical efficacy and endophthalmitis prevention, with moxifloxacin having a rate of 0.39 per 1,000 cases and gatifloxacin a rate of 0.37 per 1,000 cases.

"The overall infectious rate using fourth-generation fluoroquinolones was 0.37 per 1,000 cases, which represents a four-fold decrease from the previous period in which a third-generation fluoroquinolone was used," Jensen stated.