OD News Articles

1st October 2009

Drugs—Is Newer Better?

by Mark Maraman, OD, MS Chehalis, Washington

Advances in antibiotics have certainly improved our ability to manage ocular infections. But is newer always better? Do we sometimes bow to external pressure and abandon older therapies that are equally effective and less expensive?

Introduction

In our search to provide patients with the best possible outcomes, our job is to be critical in our assessment. In doing so, we need to realize that the medical profession is susceptible to high-profile pundits and well-designed marketing campaigns.

As we try to decide which patients and circumstances will benefit from a new medication, we should ask ourselves:

  • Is it more effective with

~ bacterial coverage
~ resistance rates
~ tissue penetration

  • Is it being used to prevent vs. treat infection?
  • What is the cost vs. benefit?

Many times, we will determine that newer meds provide substantial advantages and improved outcomes. But there may be instances when purported benefits do not meet our needs—and more importantly the needs of our patients.

Our Recent Evaluation

At PCLI we see such a large number of surgery patients that we often re-evaluate our medication protocol. Sometimes, new drugs or new data cause us to rethink how we do things. With MRSA related infections on the rise, we recently reassessed our antibiotic regimen. An important first step was a review of current evidence.

 


Staphylococcus aureus isolates sensitive (MSSA) and resistant (MRSA) to Methicillin

 


 

Current Evidence

MRSA infections are on the rise—specifically in cases of keratitis following refractive surgery and endophthalmitis after cataract surgery. There is also growing concern that MRSA related endophthalmitis is harder to treat with worse outcomes than the typical coagulase-negative Staphylococcus infections.

Results from the Ocular TRUST study, the largest collection of eye infection data in the world, show alarming changes in MRSA rates.

Several other interesting findings of the study are listed below:

  • Fluoroquinolones were the most broadly active antimicrobial agent against pathogens tested (S aureus, S pneumoniae, and H influenzae).
  • Compared to other antibiotics tested, all S aureus strains (both MSSA and MRSA) showed higher rates of susceptibility to trimethoprim and tobramycin.
  • Trimethoprim was the only antibiotic to show a high rate of activity against MRSA.
Superior Drugs?

While many have used the Ocular TRUST study to tout effectiveness and superiority of 4th generation fluoroquinolones for prophylactic use with eye surgery, a closer look at the evidence shows a different story.

It is clear that 3rd and 4th generation fluoroquinolones are effective against a broad range of common ocular pathogens. And most of us have adopted their use to treat infections like bacterial conjunctivitis and keratitis. But 2 questions beg to be asked:

  1. Are there potential weaknesses that need to be evaluated when treating an active infection or trying to prevent one?
  2. Does pre and post-op use of these drugs correlate with reduced rates of endophthalmitis?
Weaknesses

The answer to question #1 is obviously yes. Every antimicrobial has weaknesses. Otherwise, we could use one type for everything. With fluoroquinolones, there is growing evidence that even the 4th generations have high rates of resistance to MRSA.

Endophthalmitis

What about question #2? Does pre and post-op use of topical antibiotics reduce the rate of endophthalmitis? Currently, there is no definitive evidence in the literature to confirm this fact. However, despite the lack of evidence, a recent market survey found that the vast majority of surgeons use anti-infectives—86.6% pre-operatively and 94.2% post-operatively.

Evidence Ignored

So why is there such broad use of topical antibiotics (mainly fluoroquinolones) with cataract surgery? Undoubtedly fear and pressure from several external sources come into play:

  • Expert and peer opinions
  • Medical-legal concerns
  • Pharmaceutical company influences
  • Real and perceived theoretical advantages
Conclusion

We are in a constant battle to stay ahead in the fight against endophthalmitis, MRSA and other resistant microbes. The ability of pathogens to mutate and escape our defenses emphasizes the need for continuous development of anti-infectives. But an important part of our job is to assess new medications and technologies and be advocates for our patients, utilizing all tools available (anti-infectives, surgical technique, and sterile protocol) based on sound medical evidence to achieve best outcomes. If we keep our patients in the forefront, we will make good decisions. We will ensure that they receive the benefit they deserve—not just the same result for a higher price.


Endophthalmitis—Incision Type Matters

There is strong evidence that cataract surgery performed with clear corneal incisions has higher rates of endophthalmitis than those performed with scleral tunnel incisions. Several studies have demonstrated a 2 to 15-fold increase with clear corneal incisions.
One published report shows that between 1992 and 2003, the rate of endophthalmitis was:

  • 19 in 10,000 cases with clear corneal incisions
  • 6 in 10,000 cases with scleral tunnel incisions
What Works for Us

PCLI surgeons perform about 18,000 cataract procedures a year and enjoy a very low rate of endophthalmitis—less than 1 in 10,000 cases. This is well below US and worldwide averages. Several techniques help achieve this:

  • perioperative povidone-iodine antisepsis
  • mini-scleral tunnel incisions for most cases
  • tobramycin post-op for uncomplicated cases

Click here to view a clear corneal incision vs. our preferred mini scleral-tunnel incision.