Gentamicin in Pregancy

[Pharmacy Kid]

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A fellow pharmacist received orders for gentamicin for a 26 yo pregnant female admitted to hospital. She is 20 weeks pregnant and it's a high-risk pregnancy. Dx is pyelonephritis (& maybe something else). Allergic to penicillin. (This is all the info I have at the top of my head. If you want more I can go back and find out).

What would you guys do/recommend?

 

[tungsten87]

what's the infectious organism?

unfortunately your options are pretty limited for gram negative pyelonephritis. both septra and levo/cipro are category C, and while gentamicin is uncategorized it can cross the placenta and cause damage to CN VIII. i'm not sure what the best option would be in this case.

 

[glory4england]

A fellow pharmacist received orders for gentamicin for a 26 yo pregnant female. She is 20 weeks pregnant and it's a high-risk pregnancy. Dx is pyelonephritis Allergic to penicillin. (This is all the info I have at the top of my head. If you want more I can go back and find out).

What would you guys do/recommend?

Do you have any information on the penicillin allergy? Aminoglycosides have a D pregnancy risk factor with a boxed warning of potential fetal harm. How about a carbapenem like meropenem or ertapenem? The cross-reactivity with penicillin is pretty low (a few recent retrospective studies reported it to be around 1%)

But I have zero experience dealing with situations like this but that's my thought process. Curious to see what others think.

 

[rph3664]

Whenever I've dosed gent for a pregnant woman, I always started them at 1mg/kg q8h, and draw levels around the 3rd dose.

 

[Ackj]

Do you have any information on the penicillin allergy? Aminoglycosides have a D pregnancy risk factor with a boxed warning of potential fetal harm. How about a carbapenem like meropenem or ertapenem? The cross-reactivity with penicillin is pretty low (a few recent retrospective studies reported it to be around 1%)

But I have zero experience dealing with situations like this but that's my thought process. Curious to see what others think.

I agree with getting more info about the pcn, since it's very rarely a true allergy. However, I'm not sure about that 1% cross-reactivity. From what I've seen, skin testing doesn't rule out a systemic reaction, and having a positive skin test doesn't mean you will get a reaction. That said, you could always try a dose challenge/desensitization protocol if you had no other options.

Cefepime is also a viable option, since its a 4th gen and is structurally dissimilar. Covers your usual enterobacteriaciae and Pseud.

 

[rxlea]

Whenever I've dosed gent for a pregnant woman, I always started them at 1mg/kg q8h, and draw levels around the 3rd dose.

Is that a synergy dose?

 

[njac]

Ceftriaxone, FTW.

Unless she has risk factors for MDR organisms, no need for a catbepenem.

Don't forget that you can theoretically use bactrim during the 2nd trimester, but no one does.

 

[rph3664]

Is that a synergy dose?

The synergy doses I've seen were just a single dose, given at the beginning of IV therapy.

 

[cycloketocaine]

The synergy doses I've seen were just a single dose, given at the beginning of IV therapy.

Gent 1 mg/kg q8h is a synergy dose.

 

[All4MyDaughter]

The synergy doses I've seen were just a single dose, given at the beginning of IV therapy.

I'm not sure I understand how that works.

 

[cycloketocaine]

I'm not sure I understand how that works.

I'm not sure what 1 mg/kg would help anything as a one time dose. It's like pouring a cup of water to fill a swimming pool.

 

[rxlea]

Gent 1 mg/kg q8h is a synergy dose.

I'm not sure I understand how that works.

I'm not sure what 1 mg/kg would help anything as a one time dose. It's like pouring a cup of water to fill a swimming pool.

Exactly my thoughts but as a student I didn't want to be presumptuous.

 

[All4MyDaughter]

Gent 1 mg/kg q8h is a synergy dose.

Yeah.

 

[All4MyDaughter]

Exactly my thoughts but as a student I didn't want to be presumptuous.

Isn't the point that the beta-lactam enhances penetration of the AG so you can give less AG? Because that's how I learned it. But I don't use this stuff much (ok... at all) in my current practice.

 

[rxlea]

Isn't the point that the beta-lactam enhances penetration of the AG so you can give less AG? Because that's how I learned it. But I don't use this stuff much (ok... at all) in my current practice.

Yes. That's what I did on this rotation with vanco... Did that a couple times.


The vanco busts the cell wall so the AG can get in.

 

[All4MyDaughter]

I'm not sure what 1 mg/kg would help anything as a one time dose. It's like pouring a cup of water to fill a swimming pool.

or peeing on a forest fire...

 

[rxlea]

or peeing on a forest fire...

I love this analogy 😀

 

[Praziquantel86]

Check the allergy...use ceftriaxone. The vast majority of PCN allergies do not preclude the use of a cephalosporin.

On a related note, I've gotten a lot of negative pushback from high-risk OBs for using AGs in pregnant patients due to medico-legal risks. I'd be interested to see if the OB would be on board in this case, regardless.

 

[RedStarRx]

Do you have any information on the penicillin allergy? Aminoglycosides have a D pregnancy risk factor with a boxed warning of potential fetal harm. How about a carbapenem like meropenem or ertapenem? The cross-reactivity with penicillin is pretty low (a few recent retrospective studies reported it to be around 1%)

But I have zero experience dealing with situations like this but that's my thought process. Curious to see what others think.

I'd go for a cephalosporin way before the carbopenem in a pcn allergy.