ODs have a lot to learn (and un-learn) about drugs

June 29, 2013

 

San Diego-The final day of Optometry’s Meeting kicked off with a special CEE course by Ron Melton, OD, and Randall Thomas, OD, MPH. In The State of Therapeutics on Eye Care, the doctors began by pointing out that the main cause of medicolegal misadventure is “doing nothing.” Failure to diagnose is the cause of more than 35% of lawsuits vs. improper management, which accounts for less than 5%, the presenters said.

Drs. Melton and Thomas covered a range of drug-related topics. Highlights included optometry’s need to stay breast of new systemic medications, such as those prescribed for multiple sclerosis (MS), the role of older drugs, new perspectives on penicillin allergy, and drug resistance.

Drug discovery sometimes seems to move at the speed of light, but optometrists must be prepared and educated when patients present. Oral fingolimod (Gilenya) is a new once-daily pill for relapsing forms of MS. Before starting Gilenya, patients need an eye exam, which means neurologists are referring their patients to optometrists for a baseline exam, per the medical insert. Since macular edema is a side effect of Gilenya, the presenters suggested that clinicians take a baseline OCT. Macular edema usually starts in the first 3-4 months after starting Gilenya.

Dr. Thomas said that the Ocular TRUST data altered the way he practices. This nationwide study looked at susceptibility patterns in ocular isolates. Trimethoprim with polymyxin B performed best against MSSA and MRSA. In a world in which drug costs are so high, it’s worth pointing out that this is a $4 medicine, the presenters said.

Regarding penicillin allergy, the speakers pointed out that about 90% of patients with documented IgE antibodies to penicillin tolerate cephalosporins with identical or very similar side chains. First generation cephalosporins have the potential for cross-reactivity, but the risk is less than the 10% rate that has been presumed, they said. In fact, the risk is closer to 0.5%. Most second or third generation cephalosporins, specifically cefuroxime (Ceftin), cefpodoxime (Vantin), ceftriaxone (Rocephin), and cefdinir (Omnicef) are unlikely to be associated with cross-reactivity, they said.

So what are the options for true penicillin allergy patients? Drs. Melton and Thomas provided these alternatives:

  • 2nd or 3rd generation cephalosporin

  • Sulfamethoxazole/trimethoprim (Bactrim or 
Septra)

  • A fluoroquinolone (Levofloxacin)

  • Doxycycline

  • Erythromycin

One of the most controversial parts of the morning’s discussion concerned drug resistance. Conjunctival S. epidermidis repeatedly exposed to fluoroquinolone or azithromycin antibiotics rapidly develop resistance, Dr. Thomas said. But, Gentamicin, Polytrim, doxycycline, and vancomycin remain very highly effective medicines in eradicating S. epidermidis, he added.

The presenters also referenced a 2011 AJO study in which Staph. Epi. was the most common pathogen. Some 97% of all isolates were sensitive to gentamicin and fluoroquinolone resistance ranged from 32% to 40%. The high prevalence of fluoroquinolone-resistant organisms raises concern with regards to the usefulness of topical fluoroquinolones, the presenters said. In many cases, they added, some of the older generation medications are now outperforming the newer fluoroquinolones.ODT