antibiotic coverage

[NO2Noctors]

i'm going to be an ms1 soon, which means that i haven't learned a whole lot about pharm yet. i'm very interested in the ins and outs of antibiotic coverage.

here's a for instance:
suppose a person is taking a 2 week course of levoquin as a precautionary measure for prostatitis. if he loses them after one week, he decides to take the 1 weeks worth of keflex he had. will it work as well? what about penicillin? what if a person is taking a zpak for strep or something, and he loses them, but has some amoxacillin on hand, will that work as well as the zpak? assuming that he has no antibiotic allergies. i understand the "rule" that a person should not take antibiotics unless prescribed, but in THEORY, would these work? another way to ask this question would be something like if you were stuck on a desert island and had access to a crapload of several different antibiotics, but only a few days worth of each, how could you put together a course of antibiotics that would make sure that you eradicated the bug? is there any way to go besides just by antibiotic family? (furthermore, is there an abbreviation for antibiotic? ab, maybe?)

how do docs decide to prescribe antibiotics? do they culture and prescribe based on gram stain? or if they prescribe b4 the culture comes back, i guess they give a broad spectrum... but what does that mean? is it that a broad spectrum will take care of a bunch of gram negs and pos, or is it that they give a broad spectrum based on what they think the infection is most likely and the broad spectrum is broad for either a gram neg OR a gram pos. i'm really curious about how this whole "broad spectrum" concept works. and i'm especially curious about the levaquin question that i asked above.

finally, does anyone know of any good graphics or charts that illustrate antibiotic coverage. i'm picturing a sort of bar graph that compares different antibiotics sort of like this:

bug A bug B Bug C Bug D Bug E Bug F
Drug A --------------------
Drug B -------------------------------------
Drug C ---- ------------ -----
Drug D -------------
Drug E ----------------------------------------


or something like that. does that make sense?

thanks from a curious med student.

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[radslooking]

Allright, I'll jump in here.

1. Keflex would be unlikely to treat prostatitis. Usually prostatitis is a gram negative bug and keflex only covers a selected spectrum of gram positives. Its possible, but unlikely. Also, prostatitis treatment is usually longer than 2 weeks.
2. Amoxicillin may or may not treat a streptococcal organism. It is commonly used to treat children with ear infections (which can be due to strep) and other non life threatening head and neck infections....pharyngitis, otitis media, sinusitis, etc. For a streptococcal pneumonia, however amoxicillin would be likely be inadequate as the number of strep organisms that would be resistant to amoxicillin would be unacceptably high. (its a life threatening infection, therefore even 5-10% resistance would be unacceptable).
3. Doctors prescribe antibiotics usually based on what the infection is and what the likely causative organisms would be.

In any infection, it is a good idea to ask "what bug or class of bugs is causing this infection?"
skin abcesses, boils, cellulitis---usually gram positives
diverticulitis, gi abcesses--usually anaerobes, gram negatives
pneumonia--strep, staph, some gram negatives,
aspiration pneumonia-usually anearobes (klebsiella most commonly)
urinary tract infections---usually gram negatives (ecoli) with a smattering of gram positives

The table you are describing can be found in the Sanford Guide. One of the most useful books in medicine. The table you are referring to is constantly referred to. except by orthopedists They only know two antibiotics, ancef and cefazolin.

If possible, getting a culture is helpful. Examples are urinary cultures, sputum cultures, blood cultures, etc. That way, if treatment failure occurs, you know what went wrong. Also, this data is used to track susceptibilities of organisms within the hospital and the region. Also, for instance, some people have a tendency of growing the same organisms repeatedly.. (UTI's, cystic fibrosis pneumonias, etc) so sometimes old cultures are very helpful.

However, cultures require time to grow (usually 1-3 days). You can go off of gram stains, but they aren't quite as accurate, and cannot give you susceptibilities. They can only tell you...gram positive rod/chain/cluster, etc. They cannot tell you if they are resistant to certain antibiotics. Therefore you need to start "empiric" antibiotics while waiting for a culture (if you got a culture). The empiric antibiotics should cover the most common organisms causing the infection. This can be found in the Sanford Guide as well.


In practice, most physicians know the customary treatment for common infections in their head. However, the Sanford Guide or others help you out when you can't remember how long to treat a urinary tract infection in pregnant women, or whatever other wrinkle there may be in treatment.

When you say "broad spectrum" that usually means the antibiotic has a big gram positive or gram negative coverage, and sometimes both. Keflex would be narrow spectrum because it only covers a few gp's. levaquin is broad spectrum b/c it covers gn and gp and some anaerobes. pip/tazo is broad spectrum b/c it covers gn and gp.

however, you could say "we put him on broad spectrum coverage" with vancomycin and gentamicin. (vanc only covers gp's, gent only gn's).
So, broad spectrum could refer to a single antibiotic that covers gp and gn's, or could refer to a combination of antibiotics with that coverage.

i'm going to be an ms1 soon, which means that i haven't learned a whole lot about pharm yet. i'm very interested in the ins and outs of antibiotic coverage.

here's a for instance:
suppose a person is taking a 2 week course of levoquin as a precautionary measure for prostatitis. if he loses them after one week, he decides to take the 1 weeks worth of keflex he had. will it work as well? what about penicillin? what if a person is taking a zpak for strep or something, and he loses them, but has some amoxacillin on hand, will that work as well as the zpak? assuming that he has no antibiotic allergies. i understand the "rule" that a person should not take antibiotics unless prescribed, but in THEORY, would these work? another way to ask this question would be something like if you were stuck on a desert island and had access to a crapload of several different antibiotics, but only a few days worth of each, how could you put together a course of antibiotics that would make sure that you eradicated the bug? is there any way to go besides just by antibiotic family? (furthermore, is there an abbreviation for antibiotic? ab, maybe?)

how do docs decide to prescribe antibiotics? do they culture and prescribe based on gram stain? or if they prescribe b4 the culture comes back, i guess they give a broad spectrum... but what does that mean? is it that a broad spectrum will take care of a bunch of gram negs and pos, or is it that they give a broad spectrum based on what they think the infection is most likely and the broad spectrum is broad for either a gram neg OR a gram pos. i'm really curious about how this whole "broad spectrum" concept works. and i'm especially curious about the levaquin question that i asked above.

finally, does anyone know of any good graphics or charts that illustrate antibiotic coverage. i'm picturing a sort of bar graph that compares different antibiotics sort of like this:

bug A bug B Bug C Bug D Bug E Bug F
Drug A --------------------
Drug B -------------------------------------
Drug C ---- ------------ -----
Drug D -------------
Drug E ----------------------------------------


or something like that. does that make sense?

thanks from a curious med student.

 

[radslooking]

p.s. penicillin is good for very few things anymore. it can be used to treat ear and throat infections, (usually kids) and syphilis. Not too much else it's good for anymore.

 

[Mobius1985]

SDN is not the place to come for medical advice. We are random strangers and you have no way to judge if we know what we're talking about. If one loses one's antibiotics, one should be advised to call one's physician and ask to have a replacement prescribed, or a substitute suggested.

It's hard to imagine someone getting a medication as expensive as Levaquin as "a precaution" when a physical exam and/or cultures can support the diagnosis of prostatitis (from what I've read). MUCH cheaper meds are available for this problem.

For general information, consider accessing pharmacology and microbiology textbooks. (You might have trouble locating a Sanfords in a regular library before you get to medical school). Also, read about chronic prostatitis on Wikipedia at: http://en.wikipedia.org/wiki/Chronic_bacterial_prostatitis

 

[VCU07]

Allright, I'll jump in here.

1. Keflex would be unlikely to treat prostatitis. Usually prostatitis is a gram negative bug and keflex only covers a selected spectrum of gram positives. Its possible, but unlikely. Also, prostatitis treatment is usually longer than 2 weeks.
2. Amoxicillin may or may not treat a streptococcal organism. It is commonly used to treat children with ear infections (which can be due to strep) and other non life threatening head and neck infections....pharyngitis, otitis media, sinusitis, etc. For a streptococcal pneumonia, however amoxicillin would be likely be inadequate as the number of strep organisms that would be resistant to amoxicillin would be unacceptably high. (its a life threatening infection, therefore even 5-10% resistance would be unacceptable).
3. Doctors prescribe antibiotics usually based on what the infection is and what the likely causative organisms would be.

In any infection, it is a good idea to ask "what bug or class of bugs is causing this infection?"
skin abcesses, boils, cellulitis---usually gram positives
diverticulitis, gi abcesses--usually anaerobes, gram negatives
pneumonia--strep, staph, some gram negatives,
aspiration pneumonia-usually anearobes (klebsiella most commonly)
urinary tract infections---usually gram negatives (ecoli) with a smattering of gram positives

The table you are describing can be found in the Sanford Guide. One of the most useful books in medicine. The table you are referring to is constantly referred to. except by orthopedists They only know two antibiotics, ancef and cefazolin.

If possible, getting a culture is helpful. Examples are urinary cultures, sputum cultures, blood cultures, etc. That way, if treatment failure occurs, you know what went wrong. Also, this data is used to track susceptibilities of organisms within the hospital and the region. Also, for instance, some people have a tendency of growing the same organisms repeatedly.. (UTI's, cystic fibrosis pneumonias, etc) so sometimes old cultures are very helpful.

However, cultures require time to grow (usually 1-3 days). You can go off of gram stains, but they aren't quite as accurate, and cannot give you susceptibilities. They can only tell you...gram positive rod/chain/cluster, etc. They cannot tell you if they are resistant to certain antibiotics. Therefore you need to start "empiric" antibiotics while waiting for a culture (if you got a culture). The empiric antibiotics should cover the most common organisms causing the infection. This can be found in the Sanford Guide as well.


In practice, most physicians know the customary treatment for common infections in their head. However, the Sanford Guide or others help you out when you can't remember how long to treat a urinary tract infection in pregnant women, or whatever other wrinkle there may be in treatment.

When you say "broad spectrum" that usually means the antibiotic has a big gram positive or gram negative coverage, and sometimes both. Keflex would be narrow spectrum because it only covers a few gp's. levaquin is broad spectrum b/c it covers gn and gp and some anaerobes. pip/tazo is broad spectrum b/c it covers gn and gp.

however, you could say "we put him on broad spectrum coverage" with vancomycin and gentamicin. (vanc only covers gp's, gent only gn's).
So, broad spectrum could refer to a single antibiotic that covers gp and gn's, or could refer to a combination of antibiotics with that coverage.

While Keflex is a first generation cephalosporin, it does have some activity against gram negatives such as E. coli and P. mirabilis.

 

[bodonid]

SDN is not the place to come for medical advice. http://en.wikipedia.org/wiki/Chronic_bacterial_prostatitis

Medical advice? The OP is asking about academic information. Medical advice is: My girlfriend broke my ________, and now it really hurts. I took some _______, but it didn't work very well. What should I do?

 

[Mobius1985]

Medical advice? The OP is asking about academic information. Medical advice is: My girlfriend broke my ________, and now it really hurts. I took some _______, but it didn't work very well. What should I do?

I concede the remote possibility that a curious premed could have an idle inquery about such an extremely sophisticated, specific topic when most college grads don't know what a prostate is, that there's more than one microbe that can cause prostatitis, or that antibiotic resistance is a growing problem.

So say you were asked, "Theoretically, if someone's girlfriend broke their ___________, and it was painful so they took ______________ which didn't help, what would that person's therapeutic options be?" Would it not cross your mind that the query was a disguised attempt to get medical advice? Perhaps I have an overly suspicious mind. My bad. I did however suggest academic resources in case general education was the true goal.

 

[NO2Noctors]

SDN is not the place to come for medical advice. We are random strangers and you have no way to judge if we know what we're talking about. If one loses one's antibiotics, one should be advised to call one's physician and ask to have a replacement prescribed, or a substitute suggested.

It's hard to imagine someone getting a medication as expensive as Levaquin as "a precaution" when a physical exam and/or cultures can support the diagnosis of prostatitis (from what I've read). MUCH cheaper meds are available for this problem.

For general information, consider accessing pharmacology and microbiology textbooks. (You might have trouble locating a Sanfords in a regular library before you get to medical school). Also, read about chronic prostatitis on Wikipedia at: http://en.wikipedia.org/wiki/Chronic_bacterial_prostatitis

hey mobius

i was just asking about antibiotic theory (with the disclaimer that i didn't know much about pharm - not that i was a total dimwit), and i tried to give a couple of examples to get my point across, not because i'm trying to mix up a nice down-home antibiotic cocktail for my poor little prostate. what is sdn for if not to chat about (gasp!) medical stuff? no need to be such a wiener.

much thanks to everyone else who gave some pretty good answers.

 

[bodonid]

Okay, I get it. That's pretty dang cynical, though. When I was reading the OP I was thinking: yeah, I'd like to know that, too. But looking back, it was a very specific question, wasn't it?

 

[umza]

I am still interested to know if anyone knows of good graphic representation of the coverage of various antibiotic/classes vs bacteria...
I do consult Sandford's however what I am looking for is something that will help me solidify the treatments, so that I do not have to look at Sandford's everytime. I picture a Venn diagram style. Suggestions? Resources?

 

[Dirt]

I have no idea why one would want to learn antibiotic coverage as a pre-med.

 

[Habeed]

I'm guessing his example came from a clinical shadowing experience. And I'm sure he also does wonder "well, I just got sick, and I have about 5 expired prescriptions for antibiotics with a few pills left in each lying around...would it really be so bad to just take em all?" (that is, if you have one script for say, pennicillin at 4 pills/day, you would take a pill every 6 hours until you empty the bottle. Next, you'd dig up the next antibiotic and do the same. With knowledge of which ones are broad spectrum, and where the infection is, you could even take the more appropriate antibiotics first, and then move to the weaker ones) If you had just fell through a time warp to medieval Europe, or were stranded on a desert island with a fresh water supply, this might not be a bad idea.

Of course, most physicians and residents could just get a colleague to take 5 minutes and write a proper script for the correct antibiotic for the case, get cultures, and get a nice shiny bottle filled at the pharmacy with fresh pills of the correct drug.

Even if you were stuck in a third world country, and didn't want to go to a local doctor, you could usually just go to the pharmacy and get a full bottle under the counter of whatever drug was closest to a recommendation in the Sanford guide.

But if you were say a student, and your insurance had recently lapsed, and you didn't have the cash to pay for a PCP to see you, but don't want to get your credit record dinged if you go to the E.R. but refuse to pay the $800 bill...hmm...