Antibiotic Prescribing in Podiatric Medicine
I recently came across some fascinating data which breaks down the number of outpatient prescriptions written by podiatrists for all different classes of drug in 2010. Unlike various surveys that have been done over the years by different magazines, this is hard data based on the actual number of scripts. I would like to comment on some findings I find interesting in the use of antibiotics.
Antibiotics were the third most commonly prescribed class of drug following narcotic analgesics and NSAIDs with over 1.6 million scripts written. This is followed closely by antifungals at about 1.4 mil prescriptions. (Perhaps a topic for a future post?). I don’t think it would come as any surprise that cephalexin is the most prescribed (530,000) and is actually the second most common drug written by DPMs. The number two most common antibiotic would also probably not come as a big surprise, amoxicillin/clavulanic acid (Augmentin) down the line a bit at number 15 (177K). Although amox/clav is a good antibiotic with a favorable spectrum for more complicated lower extremity infections, it is probably a bit unnecessarily broad spectrum for everyday use. I have started to limit my use of this drug after I personally had to take it for an endodontic problem. First, the 875mg is an amazingly large pill which is not easy to swallow. Also, I always knew that the drug could be a bit hard on the GI tract and I knew to take it with food and a full glass of water. Despite those precautions, about 20 minutes after I took each dose, I found my stomach wanting to jump out of my abdomen! It is true what they say about how a physician can change his way of treating folks after he becomes a patient.
The third most commonly used antibiotic is trimethoprim/sulfamethoxazole (Bactrim/Septra) with 117K Rx’s. Not surprisingly, this drug’s use has increased dramatically over the past few years with as few as 34K scripts only 2 years before, a stunning increase in such a short period of time. Probably all of this usage is for the presumptive treatment of MRSA even before cultures have been returned. I have said it before; I will repeat is again here, I do NOT like to routinely use this drug. There are reasons this drug was rarely used before the MRSA epidemic we find ourselves facing. Although broad spectrum, generic and inexpensive it is not benign. Toxicities range from life threatening skin reactions, such as Stevens-Johnson syndrome to renal, neurologic, psychiatric and hematologic problems, not to mention sulfa allergy, drug-drug interactions with other sulfa based drugs and the inability to use in patients with a G6PD deficiency (and, YES, you will see this as I recently did in a patient with a multi-drug resistant Enterobacter cloacae where the ONLY drug to which the organism was reported as susceptible was TMP/SMX). Because of the lack of studies showing clinical efficacy against MRSA there is also some question as to how it should be dosed for MRSA infections. It has been suggested that the usual 1DS b.i.d. is insufficient and that should be routinely increased to 2DS b.i.d. thus potentially increasing the rate of adverse events even further. That is not to say I don’t use TMP/SMX, I just don’t routinely give it to every patient empirically to cover MRSA or even with a positive MRSA culture unless there are other reasons to use it, such as a mixed infection where the use of one drug obviates the need for combination therapy.
I often get asked the question; “if not TMP/SMX, then what oral antibiotic you using for your MRSA cases”. That depends on severity. For my more mild infections where most of you are probably using TMP/SMX, I much prefer doxycycline 100mg q12h. Minocycline can also be used. I find that there is more data to support their use and they are well tolerated even for longer courses of therapy such as in osteomyelitis. Interestingly, NEITHER of these antibiotics is found in the top 60 drugs written by podiatrists. I would like to see that change.
The next most commonly prescribed antibiotics drive me crazy! They are ciprofloxacin at 101K followed by levofloxacin at 75K. Those who have heard me lecture know that I have been preaching avoidance of quinolones, particularly ciprofloxacin since it was first released and people were sold a “bill of goods” about how broad spectrum it was and how wonderfully it penetrated bone. As time has gone on, my feelings have only intensified. If I am going to use a quinolone, it is levofloxacin rather than ciprofloxacin because of its better gram positive activity and the once daily dosing. The only time I see a use for ciprofloxacin is for a documented Pseudomonas infection, something that is extremely rare in lower extremity infections (see post on “Pseudomonaphobia”). Even then, there is no data to suggest that levofloxacin would not be equally efficacious. Another quinolone, moxifloxacin, has the advantage of better anaerobic coverage in the case of a diabetic foot infection. My quinolone usage is on a significant decline. As a class, these drugs can potentiate the development of MRSA infections, have significant toxicities and, probably most importantly, have been implicated in the development of multi-drug resistant (MDRO) gram negative infections. In fact, at Roxborough a recent antibiogram shows only about 50% of our E. coli still susceptible to ciprofloxaxin. Furthermore, I have been noticing lately that every patient who gets sent out on a quinolone invariably returns to the hospital but now with an organism resistant to the entire class. PLEASE, use these drugs sparingly and only when appropriate!!
The final drug on the list I would like to discuss is amoxicillin, currently being prescribed 28,000 times per year. This, I just don’t understand at all. Frankly, I don’t think I have ever written for straight amoxicillin nor do I see any reason to ever do so. Perhaps, if the patient presents with an infection solely caused by Enterococcus or a straight Streptococcal infection, then it may be a reasonable choice but these are extremely rare and I seriously doubt they are occurring 28K times. This leads me to believe that there is some inappropriate use of amoxicillin in the profession. Please remember that this drug is not beta-lactamase stable and is therefore ineffective against essentially all clinically relevant S. aureus.
These data reveals some interesting information about how lower extremity infections are being treated. Overall, I find the usage pretty reasonable however, when it comes to what I perceive as an overuse of TMP/SMX, quinolones and amoxicillin, we can always do better.