In this article an infectious diseases pharmacist discusses antibiotic myths.
Authored by: Timothy P. Gauthier, Pharm.D., BCPS, BCIDP
Article posted 27 October 2022
Have you ever seen the show MythBusters on the Discovery Channel? Well this blog post is not nearly as cool as that show, but it may be a fun read at least!
Here are 15 antibiotic myths to beware…
Myth 1: Stopping antibiotic courses early leads to antibiotic resistance
For decades major organizations have been saying “finish the course or you risk antimicrobial resistance” when in fact the evidence is to the contrary. Antibiotic use leads to antibiotic resistance. More use causes more resistance. Here is an article in BMJ that details the topic.
Myth 2: People can become resistant to antibiotics
Have you ever heard a statement such as “I am resistant to [insert antibiotic name]”? Well, this is not possible. Bacteria become resistant to antibiotics, not humans. People can become colonized with drug resistant bacteria, but they themselves cannot become antibiotic resistant.
Myth 3: Newer antibiotics are better
Someone once said “do not be the first to take a new antibiotic because you risk toxicity, do not be the last because you risk resistance.” New antibiotics coming to the market must have a reasonable degree of safety and efficacy to achieve FDA-approval. Antibiotics that are already on the market and widely used must maintain safety and efficacy to remain on the market. Many older antibiotics are excellent at treating infections, for example penicillin for syphilis.
While some newer antibiotics may offer some advantages, do not assume something is safer or more effective, just because it is new.
Myth 4: Antibiotics are non-toxic
To think taking antibiotics pose no risks would be a mistake. Every antibiotics comes with risks, including toxicity. This is a major reason to never take any medicine unless it is indicated. Here is a fun blog post to help memorize some antibiotic toxicities – from A to Z.
Myth 5: Intravenous antibiotics are more effective than oral antibiotics
It has been said that oral is the new IV – and I must agree. What matters when it comes to antibiotics is that the drug reaches the site of the infection in adequate concentrations to kill the bacteria. Once the bacteria are dead, it does not matter if the antibiotic was given oral or IV.
Giving IV antibiotics may be more dramatic, but that does not make it more effective for treating infections. In fact, it may actually be risker due to potential for line infections. If the gut works, use it! Here is a helpful blog post on considerations for going from IV to PO with antibiotics.
Myth 6: More expensive antibiotics are better than cheaper antibiotics
Many first-line antibiotics are cheap. For example amoxicillin prescriptions can be less than $10 and amoxicillin is an amazing drug for numerous infection types. Ciprofloxacin pills (which impressively can be given orally for Pseudomonas infection) cost only pennies.
Just because you are paying more, does not mean you are getting more or better care.
Myth 7: Old antibiotics are inexpensive
Several older antibiotics are much more expensive than you might expect. Aztreonam was approved in 1998 and still commonly costs over $100 per day. Oxacillin was approved back in the 1960s and is about $100 a day AWP today. Antifungal drug flucytosine is decades old but incredibly expensive.
Do not assume older antibiotics are cheaper. Yes it is true sometimes, but not always.
Myth 8: The antibiotic with the lowest MIC is the best
MIC stands for minimum inhibitory concentration and these MIC values are sometimes printed in susceptibility reports from microbiology laboratories. So if you are looking at a list of antibiotics and they are all marked “s” for susceptible, just pick the drug with the lowest MIC and you have the best drug, right? Wrong! These drugs and bugs are not all measured on the same scale, do not all have the same penetration to infection sites, and may not offer the same safety profile.
Antibiotic selection is complicated and while MICs can periodically guide antibiotic selection, many times they should not even be reviewed beyond S for susceptible, I for intermediate, or R for resistant.
Myth 9: Penicillin allergy labels are not a big deal
Approximately 10% of the US adult population has a penicillin allergy label and only about 10% of those labels represent true allergies. Penicillin-type antibiotics are commonly first-line antibiotics for treating infections. Inappropriate penicillin allergy labels are a scourge on our society and force us to use second- or third-line treatments. These treatments are not first-line because they are either more toxic or less effective.
Penicillin allergies are a big deal because they cause a ton of inappropriate antibiotic use. They are also a big deal because true penicillin allergies pose real dangers to patients and performing antibiotic desensitization (for a penicillin allergic neurosyphilis patient for example) is a substantial resource investment.
Myth 10: Broader is better
Antibiotics should be selected to target the most likely pathogen(s) causing infection, while also considering the patient’s risk for morbidity and mortality from the infection. Taking antibiotics not only pressures bacteria to become drug-resistant, it also negatively impacts the host’s microbiome and may lead to a C. difficile infection.
It may be surprising to hear that the most important skill of an infectious diseases physician is not knowing when to give antibiotics, rather it is knowing when not to give antibiotics.
Myth 11: When in doubt, change or add drugs
Many times an infection is not a patient’s only problem. A failure to respond is not always a failure to cover and may be due to other medical conditions or lack of source control.
When in doubt, it may be time to call in an infectious diseases expert’s consultation, rather than going right to changing the antibiotic regimen. Numerous antibiotic changes in a short period of time can easily do more harm than good.
Myth 12: Response implies diagnosis
Patients with non-infectious issues are often started on empiric antibiotic therapy. After all, it is not like a patient walks into an Emergency Room with their diagnosis written on their chest! However, once a patient is clinically improving it is essential to assess whether it was the antibiotics or controlling an alternative diagnosis that was the reason for clinical improvement.
Myth 13: Polymicrobial infections require multiple antibiotics
Almost all antibiotics kill a wide array of bacteria. If a patient has more than one pathogen causing infection, it is fairly often that a single antibiotic can do the job. Sometimes we do need more than one antibiotic for polymicrobial infections, but this is often not the case.
Myth 14: Bigger disease, bigger or newer drugs
Just because a patient has a severe infection, it does not mean they always need numerous antibiotics or newer antibiotics. In fact, many bacteria that cause severe infections are highly susceptible to some of our oldest antibiotics.
Examples of this include flesh eating bacteria (i.e., Streptococcus pyogenes aka beta-hemolytic Group A streptococci) and gas gangrene (i.e., Clostridium perfringens). The drug of choice for these bugs? Penicillin, which has been in routine clinical use since the 1940s!
Myth 15: Cidal is better than static for antibiotics
While at face value a bactericidal antibiotic would seem clinically superior to a bactericatstic antibiotic, but it turns out the evidence does not support this to be routinely true. Here is a blog post from the guru himself Dr. Brad Spellberg on this issue.
In the 1940s Alexander Fleming warned about antibiotic misuse leading to resistance in his Nobel Prize speech. Today we still struggle with heeding his warnings. Knowing myths helps us use antibiotics wiser. Hopefully this article about antibiotic myths was helpful, now go be an antibiotic ninja!
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