Thread by @drtimothyli

Ceftriaxone is obviously not a popular choice for MSSA bacteremia among #IDtwitter

There is no prospective data showing it's inferior to other options so far

So why?

First of all, why ceftriaxone?

Most common reason: once daily dosing which makes it good for OPAT

There are 2 flaws here...

1. Once daily dosing

fT>MIC is the 🔑 PK/PD parameter for beta-lactams

Limitations of ceftriaxone:
1. Highly protein bound ➡️lower free drug concentration
2. MIC for MSSA unknown (inferred susceptibility) or too high

Therefore optimal fT>MIC may not be achievable with 2g q24H

This study shows that cefazolin 2g q12H (i.e. not even the full dose we normally use for MSSA) works much better than ceftriaxone 2g q24H

pubmed.ncbi.nlm.nih.gov/29635472/

2. OPAT

To quote @BradSpellberg, there's no RCT showing IV is superior to oral, while oral is proven to be at least equally efficacious as IV

Oral switch works in SAB (even those with IE) so it should be done whenever feasible

If IV therapy has to be continued:

• Cefazolin or anti-staphylococcal penicillins should be preferred

• Daptomycin is probably a better option for OPAT, in terms of efficacy and ⬇️collateral damage (no unnecessary Gram neg coverage), but it's 💸💸💸

So is there any role for ceftriaxone in MSSA bacteremia?

•2g q12H?
•For particular types of infections e.g. osteoarticular?
•As an alternative towards the end of therapy after clearance of bacteremia?

@BradSpellberg @DrToddLee @syctong @Josh_S_Davis @IdVilchez
Your thoughts?