Synopsis
Review antimicrobial prescriptions as active clinical decisions, switching safely from intravenous to oral treatment when physiology, absorption, source, pathogen and available oral exposure all support the change.
- Every antimicrobial needs an indication, agent, dose, route, start time, review time and intended duration or stop criterion visible in the record.
- Review at 48 to 72 hours using diagnosis, cultures, source control, physiology and toxicity: stop, narrow, switch, continue with an end date or revise the diagnosis.
- IV-to-oral switch requires clinical improvement, stable haemodynamics, functioning gastrointestinal absorption and an oral option that achieves adequate exposure at the infected site.
- Oral does not mean weak: high-bioavailability agents can produce reliable systemic exposure, while some oral beta-lactams are unsuitable for infections needing sustained high concentrations.
- Some infections need specialist plans before switching, including endocarditis, meningitis, severe bone or joint infection, undrained abscess and Staphylococcus aureus bacteraemia.
- Shorter evidence-based courses reduce toxicity and resistance; persistent biomarkers alone should not extend treatment when the patient and source have improved.
Key red flags
Shock, escalating oxygen, persistent bacteraemia, vomiting, ileus, malabsorption or a high-risk deep focus argues against routine oral conversion.
Investigation priorities
Establish whether infection and organ dysfunction are genuinely improving.
Management branches
Empirical antimicrobial therapy has continued long enough for early response and microbiology to become available.
- Reconfirm diagnosis and source, assess physiology and toxicity, review cultures, imaging, procedures and all administered doses.
- Choose stop, narrow, IV-to-oral switch, continued IV with indication, or broaden only for a new supported hypothesis; document rationale.
- Set total duration and next review, update allergy and resistance information and communicate pending results to the responsible team.
Key medicines
Amoxicillin oralA common adult dose is 500 mg orally three times daily; severe indications may require higher guideline doses.Check immediate beta-lactam allergy, renal function and indication; avoid using this example for meningitis, endocarditis or resistant organisms without specialist guidance.
Doxycycline oralCommon adult treatment is 200 mg on day one then 100 mg once daily, with regimen varying by indication.Review pregnancy, oesophageal irritation, photosensitivity, hepatic disease and cation-containing antacids or supplements; take with water while upright and use syndrome-specific duration.