Antibx Test Dose

[Noyac]

Who is giving them?

How much do you give?

Why do you give a test dose?

Is it reliable?

Who do you give a test dose to?

I am curious as to what others are doing. I never give a test dose of ancef to a PCN allergic pt unless you want to call 1 gm IV push a test dose. If they have had any rxn to ancef in the past then they give something else.

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[VentdependenT]

I think the test dose is bogus.

If the patient is going to have anaphalaxis its gonna happen no matter how small the IV dose (even skin prick testing can elicit disaster).

Only reason to give cephalosporins slow is because its killing is time dependent. On the flipside the aminoglycosides possess concentration dependent killing.

 

[Noyac]

So what do you do for a pt with PCN allergy?

 

[IceDoc]

Who is giving them?

How much do you give?

Why do you give a test dose?

Is it reliable?

Who do you give a test dose to?

I am curious as to what others are doing. I never give a test dose of ancef to a PCN allergic pt unless you want to call 1 gm IV push a test dose. If they have had any rxn to ancef in the past then they give something else.

Our Hospital has an extensive preoperative antibiotic administration program, and our ID people assure us there is absolutely no reason for a test dose (I'd look it up myself, but I'd rather read up on other topics).

From my perspective, what's the point? A "mini" anaphylactic reaction? More likely you'll give a test dose, then the patient will become hypotensive for some other reason, and they'll end up with a bunch of allergist bills for a workup they don't need and a new red flag on their chart.

So in answer to your questions: Not me. The full dose (usually 2g or 50mg/kg). No. Nobody.

 

[IceDoc]

So what do you do for a pt with PCN allergy?

Usually Clinda.
If rxn was just a rash, then the lit says go with cephalosporin. However, any other reaction and it's prudent to get testing before administering cephalosporin. The cross-reactivity between pcn and cephalosporin is something like 10%, so statistically you should be OK most of the time. But it might be really bad once. And most of the time the person can't remember the reaction, and I'm certainly not going to have testing done, so I'll just use Clinda.

Vanc can also be used, but we only use it in situations like hardware placement, CPB.

 

[Noyac]

Very good everyone. Thats my approach as well. I just give the full dose.

I asked this b/c as I was walking throught pre-op area, I overheard a nurse saying Dr. Soandso wanted a test dose of ancef b/4 the procedure. The Dr was not an anesthesiologist.

I also supervised crna's in the past and they always gave a test dose. I tried to explain that it was a waste of time but they didn't care to listen to me.

 

[CremeSickle]

this has come up on a NUMBER of occasions. The test does IS BS. If you are going to have an anaphylactic rxn to something it will happen with 2 ccs or all of it equally. There isnt any evidence to suggest a test dose makes any sense.

 

[tussionex]

a pharmacy policy in one hospital that i work at is to NOT call the md about PCN allergy and cephalosporins ordered due to statistically insignificant incidence of cross reactivity.
i wouldn't recommened a test dose nor would i bother a doc with an alternate abx.

 

[Planktonmd]

a pharmacy policy in one hospital that i work at is to NOT call the md about PCN allergy and cephalosporins ordered due to statistically insignificant incidence of cross reactivity.
i wouldn't recommened a test dose nor would i bother a doc with an alternate abx.

I wouldn't call the cross reactivity " statistically insignificant " !

 

[beezar]

a pharmacy policy in one hospital that i work at is to NOT call the md about PCN allergy and cephalosporins ordered due to statistically insignificant incidence of cross reactivity.
i wouldn't recommened a test dose nor would i bother a doc with an alternate abx.

I don't know... what if the pt had a anaphylactic reaction to PCN? I personally would just avoid cephalosporins in that case.

 

[Mman]

It's very rare that I've seen somebody with anaphylaxis listed as their allergy to penicillin or anything that sounds remotely close.

95% of the time it's "I got a rash" or "it made me itch" or "it made me nauseous" or "I can't remember and haven't had it since I was a little kid". I used to completely avoid giving ancef to those patients, now I hardly bat an eye.

 

[tussionex]

I wouldn't call the cross reactivity " statistically insignificant " !

i don't either. i took basic stats just like everyone else and think 6% incidence might be deemed "significant". i was just stating our policy. personally, i like to verify the nature of the reaction with nursing and then take it from there....will even do it with ER patients and sometimes with carbapenems as well. i still don't advocate a test dose.

 

[epidural man]

So what do you do for a pt with PCN allergy?

I say "Noted"

I don't give a test dose, but I do try to push it slowly if I don't have one of those bag from pharmacy.

Also, perhaps overkill, but I if I am intubating the patient, it makes me feel better to give the Abx after the tube is in - just in case.

Sadly, there are a few complications I never ran into as a resident, so now I will have to face them head on as a staff when they do happen. I think that kind of sucks. Anaphylaxis is one of them.

 

[Laurel123]

No test dose. I give it slowly usually when it is convenient. Patients that had a rash, redness or itching dont concern me. If they say 'anaphylaxis' then I dont mess with test doses, I just give clinda. Then there are the patients that have 'swelling' or SOB, it is hard to know what to make of it.

 

[Arch Guillotti]

I think the test dose is bunk also. I also think that the vast majority of pcn "allergies" are bunk as well. I always ask pts. what the pcn does to them and it is almost always a "rash" or a something they were told as a child and it has followed them around ever since. An allergy and immunology attending once told me that the VAST majority of people outgrow their childhood pcn allergies, even if the allergy is very real.

Anecdotally, but very true - I have only seen one case of anaphylaxis from Abx thus far. The case was a heavy duty multilevel spinal fusion in a young girl with secondary scoliosis (ie bloodbath). Sometime towards the end of the case I redosed the Abx and shortly thereafter she developed some degree of hypotension that just really didn't get better w/volume. My experience with these cases is that low bp is always because you are behind on volume. This time it was not. We kind of gimped along w/volume till the end. When the case was finished and she was turned prone and all the drapes came off it was obvious what happened - she had a diffuse rash over her entire body. At that point she got steroids, etc. I felt pretty dumb at that point, after all there was a temporal association between abx administration and hypotension. However, there was also A LOT of bleeding at that point in time. My very experienced attending didn't catch it either so then I didn't feel so bad. the girl ended up doing fine.

 

[cfdavid]

So what do you do for a pt with PCN allergy?

Aztreonam??

 

[Noyac]

Aztreonam??

What?

How much does that **** cost?

 

[epidural man]

I felt pretty dumb at that point, after all there was a temporal association between abx administration and hypotension. However, there was also A LOT of bleeding at that point in time. My very experienced attending didn't catch it either so then I didn't feel so bad. the girl ended up doing fine.

You are probably right, however, every case I have heard about in M & M that was most likely anaphylaxis was never cut and dry. Even in your case you could say that it could be latex, iodine, blood products, redosing of NMB. Most likely (as you point out) it was the abx because the time course fits, but I guess you can't REALLY tell unless you do post op testing.

 

[VentdependenT]

What?

How much does that **** cost?

A ton.

 

[Noyac]

A ton.

Exactly

 

[tussionex]

Aztreonam??

probably not from my pharmacy.

any thoughts, sdn1977? you are far more the budget guru than i am!

 

[cfdavid]

What?

How much does that **** cost?

Christ. You'd think they could tell us this when learning pharm. That's like "Linezolid has great activity against MRSA" "But, we don't really use it".....
Ah, o.k. Should I bother to memorize it???

WTF? Then, in the last lecture, they actually DID state why. Supposedly, Linezolid is multiples more expensive than other equally efficacious alternatives such as Vancomycin and Daptomycin, and orals such as TMP/SMX or doxycycline.... Kind of important to know, so that we don't go around looking like fools suggesting "hypothetical" meds come 3rd year......

 

[lord_jeebus]

According to this paper, the positive likelihood ratio of true PCN allergy in patients with self-reported PCN allergy is only 1.9.

http://jama.ama-assn.org/cgi/content/full/285/19/2498?ijkey=d4d9b9dc3a0698efe62f781e0a9d0c4d673de4ec

I did read a paper at some point that showed that people who self-report PCN allergies are much more likely to complain of adverse reactions to all classes of drugs.

 

[proman]

Aztreonam is about the same cost as Unasyn ($50 or so for 1 day), so it's much cheaper for 1 time dose.

You'll use linezolid almost everyday in the ICU. I used it on the wards during my internship too.

 

[cfdavid]

Aztreonam is about the same cost as Unasyn ($50 or so for 1 day), so it's much cheaper for 1 time dose.

You'll use linezolid almost everyday in the ICU. I used it on the wards during my internship too.

Man, that's not the way the PharmD made it sound during lecture (we're doing a pretty cool integrated pharm, with all of our micro and then pathophys etc.). This guy knows his stuff and is an ID specialist at our schools major hospital. He made it sound like he doesn't really dispense that much Linezolid. Who knows, I also know that Abx's can be somewhat regional, if for no other reason than resistance etc.

 

[Noyac]

Christ. You'd think they could tell us this when learning pharm. That's like "Linezolid has great activity against MRSA" "But, we don't really use it".....
Ah, o.k. Should I bother to memorize it???

WTF? Then, in the last lecture, they actually DID state why. Supposedly, Linezolid is multiples more expensive than other equally efficacious alternatives such as Vancomycin and Daptomycin, and orals such as TMP/SMX or doxycycline.... Kind of important to know, so that we don't go around looking like fools suggesting "hypothetical" meds come 3rd year......

Sorry, I wasn't trying to be an ASS.

 

[fakin' the funk]

Man, that's not the way the PharmD made it sound during lecture (we're doing a pretty cool integrated pharm, with all of our micro and then pathophys etc.). This guy knows his stuff and is an ID specialist at our schools major hospital. He made it sound like he doesn't really dispense that much Linezolid. Who knows, I also know that Abx's can be somewhat regional, if for no other reason than resistance etc.

Probably personal preference.

But linezolid is a common po med for outpt tx of MRSA, or for MRSA pts who are vancomycin-allergic, or for Bactrim-intolerant pts, etc etc

 

[lord_jeebus]

When I was on Transplant we threw around Linezolid like candy.

Elsewhere I found that its use was quite restricted.

 

[cfdavid]

When I was on Transplant we threw around Linezolid like candy.

Elsewhere I found that its use was quite restricted.

Yeah, I'm sure it varies with different "cultures" in hospitals and regionally etc.

What about erythromycin? We were told of many drug interactions that make it less favorable, and was even taken off the "list" at a major medical center associated with our med school. So, apparently, they don't use it there either. We were told of it's GI motility "side effect" that surgeons used to really like. Any real world feedback?

 

[cfdavid]

Probably personal preference.

But linezolid is a common po med for outpt tx of MRSA, or for MRSA pts who are vancomycin-allergic, or for Bactrim-intolerant pts, etc etc

Perhaps the po aspect makes it convenient, versus vanco or dapto that are IV (only?).

 

[cfdavid]

One thought on penicillin allergies is that, according to our PharmD ID specialist, though most publications will "report" cross reactivity of Penicillin allergy with cephalosporins at 5-10% (which is what we should remember for board exams etc....), but the actual cross reactivity with 3rd generation cephs (ceftriaxone, cefotaxime) would be close to ZERO. He did not elaborate as to why, though. And with 2nd gen resp cephs (cefalcor, cefuroxime, loracarbef), it would "really" be closer to 1%..... Same for 1st gen.

Again, he didn't elaborate WHY. Perhaps SDN1977 could elaborate.

 

[lord_jeebus]

One thought on penicillin allergies is that, according to our PharmD ID specialist, though most publications will "report" cross reactivity of Penicillin allergy with cephalosporins at 5-10% (which is what we should remember for board exams etc....), but the actual cross reactivity with 3rd generation cephs (ceftriaxone, cefotaxime) would be close to ZERO. He did not elaborate as to why, though. And with 1st gen cephs (cefalcor, cefuroxime, loracarbef), it would "really" be closer to 1%..... Same for 2nd gen.

Again, he didn't elaborate WHY. Perhaps SDN1977 could elaborate.

Some penicillins share side-chain structure with 1st or 2nd generation cephalosporins, but none with 3rd/4th gen. There is evidence that the vast majority of anti-PCN antibodies bind to side chains, not the beta-lactam ring.

Another issue is that penicillins have degradation products that form conjugates with other proteins (setting off immunologic issues) but cephalosporins do not. Thus even with the same side-chain, a pt with PCN allergy may not react to a 1st gen cephalosporin.

Finally, the old studies from the 70s that showed 8-10% cross-reactivity were flawed in numerous ways, most notably in that the cephalosporins were contaminated with penicillin.

 

[cfdavid]

Some penicillins share side-chain structure with 1st or 2nd generation cephalosporins, but none with 3rd/4th gen. There is evidence that the vast majority of anti-PCN antibodies bind to side chains, not the beta-lactam ring.

Another issue is that penicillins have degradation products that form conjugates with other proteins (setting off immunologic issues) but cephalosporins do not. Thus even with the same side-chain, a pt with PCN allergy may not react to a 1st gen cephalosporin.

Finally, the old studies from the 70s that showed 8-10% cross-reactivity were flawed in numerous ways, most notably in that the cephalosporins were contaminated with penicillin.

Ah, yes, he DID mention this as the major reason. Thanks.

 

[tussionex]

Perhaps the po aspect makes it convenient, versus vanco or dapto that are IV (only?).

vanco is available as capsules and we make oral solution, but it is not bioavailable outside the GI tract. we use it for c.diff mostly

dapto = iv only. we do a lot of dapto outpatient infusions at our infusion center, however.