The Q-Wave: Bugs and Drugs

By February 27, 2019 No Comments
The Q-Wave Newsletter

Welcome to The Q-Wave, where our whole goal is promoting clinical excellence and discussing the issues that are pertinent to clinical practice. If you love our monthly newsletter, you’ll love our live conferences and podcast just as much.

In 2019, we have three conferences. They’re four-day conferences where you’ll spend half the day in the classroom and half the day enjoying these awesome destinations.

Vital Emergency Medicine is coming to Key West in April. This is a foundational curriculum for anyone who practices emergency medicine. It’s going to focus on diagnostics; we’ll make sure you’re really good at your labs, chest radiographs and EKGs. This is designed for practitioners who take care of sick people: chest pain, shortness of breath and abdominal pain.

Urgent Care Summit will be held in Alaska in July. This conference will be talking about the patients you don’t expect to get admitted. It’s the earaches, sore throats, lacerations, orthopedics, superficial infections and mild head injuries. Our whole goal is to optimize your confidence and competence. We want to teach you how not to get burned in this high-risk environment.

Critical Access Emergency Medicine is taking place in Yellowstone in October. This is an advanced emergency medicine curriculum. Make no mistake about it: this is for critical access PAs (or those aspiring to get to that level) who take care of really sick people. If you take care of codes, intubation, central lines, LPs, DKA and septic patients with a systolic pressure of 60, then this conference is for you.

Welcome to Part 2 of our discussion on antibiotics. If you missed Part 1 of this series last month, visit our podcast, Talk EM. You can also watch Part 1 and Part 2 on YouTube!

If you’ve been following me, you know I have a theory, a philosophy, that advanced practitioners (myself included) are very weak on antibiotics and addiction. I’m trying to fix one of these big gaps with this series on antibiotics. You have to know the antibiotics and how they fit into clinical application.

Let’s start with an overview, which you can remember with this mnemonic: CVG MM TT. I want you to remember those letters using a picture in your mind of a man. His head is the letter C, he has a V-neck sweater and a pendant with the letter G. CVG stands for clindamycin, vancomycin and gentamycin. This man has two big, bulging muscles and those are the two Ms, which stand for Macrodantin (nitrofurantoin) and metronidazole. You can’t forget this man’s arms, which are two Ts. That stands for trimethoprim/sulfamethoxazole and tetracycline.

Then, we have four classes: penicillins, cephalosporins, fluoroquinolones and macrolides. You need to be able to have an intelligent conversation about each one of these 11 antibiotics.

Clindamycin

We’re going to start with clindamycin. It’s really good for gram-positives and anaerobes. When we talk about anaerobic infections, like aspiration pneumonia, your question should be, “Do you want to use clindamycin or metronidazole?” Clindamycin has anti-toxin effects, so it’s considered one of the better drugs for toxic shock syndrome and necrotizing fasciitis. It’s pretty reasonable for treating people who are really allergic to penicillin. Remember, if someone’s allergic to penicillin there’s a chance of cross-reactivity to cephalosporins. Textbooks note a rate of about 10%, but clinically, it’s lower than that.

Clindamycin is highly linked to C. Diff; they say about 10%, which I think is probably high. Overall, I don’t think you should use it.

Vancomycin

Vancomycin is for gram-positives. It’s the opposite of gentamycin, which is only for gram-negatives. Vancomycin is the heavyweight champion for MRSA and C. Diff. In fact, it’s now the first-line agent for C. Diff because oral vancomycin isn’t absorbed well. We like to use vancomycin if we have someone with healthcare-acquired pneumonia (vancomycin and Zosyn) or meningitis (ceftriaxone and vancomycin). When you treat with vancomycin, look for an allergic reaction that presents as a nasty rash referred to as red man syndrome.

Gentamycin

Gentamycin is nephrotoxic based on the duration of therapy. We’ll hit people really hard with gentamycin but try to get them off it as quickly as possible to avoid renal failure. There’s some ototoxicity associated with it – just a bad roll of the dice where you get one or two doses and you can’t hear so well.

Metronidazole

Metronidazole, or Flagyl, is really good for anaerobic infections like C. Diff, protozoans, giardia and trichomonas, and E. histolytica (liver abscesses). It’s one of the primary regimes for H. pylori. This is the drug of choice for most anaerobic infections.

Again, I use aspiration pneumonia as an example. If I see aspiration pneumonia, I make sure they’re put on metronidazole. As a general rule, if someone has an infection in their belly, Cipro Flagyl is a time-tested cocktail. Remember, there is an Antabuse reaction, so we try to avoid using metronidazole with alcohol. When you encounter trichomonas, remember this: if it’s flagellated, give them Flagyl. So, trichomonas gets two grams of oral Flagyl. You have to treat their partners too.

Macrodantin

Nitrofurantoin, or Macrodantin, is a broad spectrum antibiotic. It’s good for gram-positives and most gram-negatives. A seven-day course is really good for UTIs. It doesn’t work in pyelonephritis though. How do you know someone has pyelonephritis? I would say cystitis is to pyelonephritis what an STD is to PID. You have two superficial infections and one deep infection. Pyelo is a deep UTI, a deep upper general urinary infection, so we really wouldn’t use nitrofurantoin for that.

Trimethoprim/Sulfamethoxazole

Bactrim is the drug of choice for a patient with HIV positive status and bad pulmonary disease. You have to be concerned about Pneumocystis jiroveci pneumonia. Bactrim is reasonable for toxoplasmosis, which is typically acquired from cat droppings or Listeria.

We also use Bactrim for things like UTIs. You could use it for salmonella infections, and possibly for respiratory infections like bronchitis or otitis media. It’s reasonable for MRSA, where the dose is one to two double-strength tablets BAD. Most people only use one, but you can always do two DS tablets BAD and Sanford Guide talks about that. Don’t ever, ever, ever use it with warfarin. It will increase a patient’s INR to about seven or eight within two or three doses.

Tetracyclines

Here, we’re referring to doxycycline, which is the quintessential antibiotic. It’s great for community-acquired pneumonia, where we use a very invasive treatment: 100 BAD for 10 days. Doxycycline is reasonable for softened tissue infections where we’re thinking MRSA. It’s the drug of choice for Lyme disease. However, we want to avoid doxycycline in kids less than eight because it messes with calcium in their bones and teeth. It is photophobic and, as a pleurodesis agent, irritates the chest cavity.

If someone’s lung keeps collapsing from a pneumothorax, you want to keep it up. You’d use a little doxycycline. You have to be aware that it is inflammatory toward mucosal membranes. Therefore, it can cause difficulty swallowing

Penicillin

We use penicillin for strep or syphilis and that’s really it. Penicillin won’t touch the skin, because staph lives in the skin, and mold, where penicillin came from, is in the skin. You really have no effectiveness against staph. So, they made a new class of antibiotics to kill staph.

The second generation penicillins are your anti-staphylococcal penicillins: methicillin, nafcillin and oxacillin. This does cover non-MRSA staph, but no MRSA coverage. So, we use them for skin infections like cellulitis and osteomyelitis. If we’re concerned about endocarditis from IV drug use, we’d probably go to vancomycin, but penicillin is still an option.

The aminopenicillins are ampicillin and amoxicillin, where it’s a super potent amoxicillin. They have some gram-positive coverage and some gram-negative coverage but will not cover MRSA. We would never use aminopenicillins for a skin infection; it’s used for upper respiratory tract infections, such as sinusitis and otitis media, Listeria, UTIs and Lyme disease.

When it comes to the fourth-generation penicillins, Zosyn is our heavyweight champion. Piperacillin/tazobactam is powerful for gram-positives and gram-negatives, including Pseudomonas. It really is like a nuclear bomb, very potent. It’s the best one and I feel most PAs will use it. When I have someone who’s really septic and I don’t know why, they’re getting 3.375 or 4.5 grams of Zosyn. It usually doesn’t cover MRSA, but overall, vancomycin and Zosyn cover most of the really bad stuff.

Cephalosporins

There are a lot of cephalosporins. I believe you need to know the first generation and the third generation. Cefazolin or Ancef (IV) and cephalexin or Keflex (oral) are the two first-generation cephalosporins I think you need to know. They’re good for mild to moderate nonpurulent cellulitis if you don’t highly suspect MRSA. They do have some MRSA coverage. Cefazolin is typically used before surgery, especially hand surgery; cephalexin is really good for UTIs. Remember, E. Coli is the number one bug in UTIs and cephalexin covers E. Coli about 97% of the time. It’s also very safe in pregnancy.

The most important third-generation cephalosporin is ceftriaxone, or Rocephin. This is a great antibiotic for most gram-positives and gram-negatives, except Pseudomonas and anaerobes. We use ceftriaxone often for community-acquired pneumonia with azithromycin. That’s the same cocktail we use for an STD, with different doses and different frequency. Ceftriaxone is our heavyweight champion for treating meningitis.

Macrolides and Fluoroquinolones

Now, this is kind of cool; I think so at least. You have the macrolides and the fluoroquinolones. There are three primary ones in each class and the first antibiotic in the class wasn’t as good as the follow-ups. The first macrolide is erythromycin and the first fluoroquinolone is ciprofloxacin. Erythromycin is really good for gram-positives and atypicals, but no gram-negatives. Cipro is the opposite: really good for gram-negatives and not so much for gram-positives.

Macrolides, which also include azithromycin and clarithromycin, are pretty good for atypical organisms like chlamydia, mycoplasma and legionella. Erythromycin is not so good for gram-negatives. Most people think it’s the drug of choice for strep throat when the patient is highly allergic to penicillin. It does cover some gram-positive cocci and some gram-negative cocci, where the azithromycin is a more in-depth antibiotic. Even though the Z-Pak of azithromycin is a five-day course, it does stay in the body for about two weeks. It’s just not a very strong antibiotic. Clarithromycin is the strongest antibiotic in the macrolide class, hands down.

Fluoroquinolones, including ciprofloxacin, moxifloxacin and levofloxacin, do pretty much everything well. Cipro doesn’t cover gram-negatives well, but moxifloxacin and levofloxacin can be used for anything: gram-negatives, gram-positives, atypicals, anaerobes and Pseudomonas.

However, there are a lot of problems with this class. Colleagues, if you get nothing else from this newsletter, get this: try not to use them as a first line agent, because they cause QT prolongation, increased tendon rupture, and an increase in liver function. It’s teratogenic in kids, and there are some real dysglycemia issues between hypo- and hyperglycemia.

In 2018, the FDA published a report about fluoroquinolones, saying they’ve caused 67 life-threatening cases of hypoglycemia and coma with 13 deaths and 9 permanent disabilities. My advice is to use them gently as a second line agent. If you’re going to use fluoroquinolones, you need to document why you didn’t go with something without so many side effects.

My hope is that this is useful to you. Thank you for reading. Please share it with your colleagues if you feel they would benefit from this information. If there’s a newsletter topic you feel would be helpful, please let us know. We’ll use your suggestions for the Q-Wave, for podcasts or even a YouTube video.