Empirical Oral Switch Options in NHS A&A

Direct IV to PO conversion 

If the agent(s) used in the current antimicrobial regimen exist(s) in an oral formulation, use the oral formulation.  

Exception: IV vancomycin cannot be converted to oral vancomycin as this is not absorbed from the lumen of the gut. Oral vancomycin must not be used for any indication other than treatment of C.difficile infection. 

The oral “version” of IV benzyl-penicillin is penicillin V. 

High bioavailability agents are preferred for early IVOS. 

Conversion of agents not available in PO formulation 

If the current regimen or one or more of its components is not available in an orally absorbed formulation, you MUST review both current and past microbiology results to decide which IVOS option is most appropriate for your patient: 

Gold Standard = Culture-based IVOS: Use most narrow spectrum oral option reported on a current isolate from the site of infection. 

Silver Standard = Informed Empirical IVOS: If there are no up-to-date results from the current site of infection, use previous isolates from the site to inform IVOS options. 

Bronze Standard = “Blind” IVOS: The table below only applies in the total absence of current or previous isolates that could inform antimicrobial choice. It is a last resort option, and response must be carefully monitored.  

If a patient on the Bronze Standard fails to improve or develops new signs of sepsis, DO NOT rotate to another blind oral agent. Escalation to IV therapy and immediate discussion with Microbiology is mandatory. 

Table 2: Blind ("Bronze Standard") IVOS options - use with caution.

Indication IV Regimen Bronze Standard ("Blind") IVOS

Hospital-acquired pneumonia (HAP)

Co-trimoxazole + Gentamicin 

OR

Amoxicillin + Temocillin

Co-trimoxazole* oral 960mg 12 hourly

Intra-abdominal infection, e.g. biliary sepsis, appendicitis 

(Amoxicillin OR Vancomycin) + Gentamicin + Metronidazole

Co-trimoxazole* oral 960mg 12 hourly + Metronidazole oral 400mg 8 hourly
Skin and soft tissue infection  Vancomycin

Doxycycline* oral 200mg on day 1 and 100mg once daily thereafter

Spontaneous bacterial peritonitis (SBP) 

Amoxicillin + Temocillin

Co-trimoxazole* oral 960mg 12 hourly

Urosepsis 

Gentamicin +/- (Amoxicillin OR Vancomycin)

Cefalexin oral 1g 8 hourly

*Doxycycline and co-trimoxazole are contraindicated in pregnancy. Contact microbiology for advice if required.

IV to PO switches for empirically used ultra-broad-spectrum antimicrobials 

There are usually no oral agents that can replicate the same spectrum of coverage of ultra-broad-spectrum agents like carbapenems (e.g. meropenem, ertapenem) or piperacillin-tazobactam, and these agents are often used for isolates with no oral treatment options.  

If their use has been truly empirical – i.e. there are no current or previous isolates that have dictated choice of the agent: 

  1. For infections without deep-seated component, e.g. HAP: complete a 5 day course of the ultra-broad-spectrum IV agent, then stop without IVOS.
  2. For complicated and/or deep-seated infection, e.g. intra-abdominal collections: discuss with a microbiologist. 

 

Guideline reviewed March 2026
Page updated July 2026



;