Oral or intravenous antimicrobial therapy
A clinically unstable patient may often initially require intravenous antimicrobial therapy. However, switching to oral therapy once they are improving has big advantages, and one relatively easily achievable AMS goal is ensuring this switch is made in a timely way when this is appropriate.
Switching could be built into the prospective audit and feedback approach, or the pharmacy might take responsibility for reminding clinicians of the need for reassessment if there is no electronic prescribing system to do this.
Now watch Video 3, which has been taken from a larger WHO course on AMS, and answer the following questions.
Transcript: Video 3 Pharmacology of antimicrobials for clinicians (continued) (WHO, n.d. 3).
Bioavailability, or the amount of active drug that reaches the bloodstream after administration, is a key pharmacokinetic property of each antimicrobial. Highly bioavailable oral antibiotics are those that achieve serum concentrations comparable to antibiotics administered intravenously.
Although many hospitalised patients initially receive empiric intravenous antimicrobials due to clinical instability, the course of therapy for many common infections may subsequently be completed with orally administered drugs. Switching to oral antibiotics when appropriate can decrease costs, facilitate discharges and save patients from complications associated with indwelling intravenous catheters, including infection and clots.
In order to determine when oral antimicrobial therapy is indicated, clinicians can ask themselves the following questions:
Is the patient haemodynamically stable? If the answer is no, then intravenous antimicrobial therapy may be warranted. In hospitalised patients that had initially received intravenous antimicrobials, the clinician should assess the patient’s clinical trajectory. If they’re improving clinically, switching from intravenous to oral antimicrobials may be appropriate.
Is the patient eating or tolerating enteral feeding? Patients with persistent nausea and vomiting may not be candidates for orally administered antimicrobials.
Is the patient able to adequately absorb orally administered medications? Patients with an active gastrointestinal bleed, or those with ileus, bowel absorption syndromes or proximal resection of their small intestines may not be candidates for orally administered antimicrobials.
Is there an orally bioavailable antibiotic that could be used to treat this infection? Bioavailable oral antibiotics that are commonly prescribed in practise include fluoroquinolones, doxycycline, azithromycin, trimethoprim-sulfamethoxazole, metronidazole, linezolid and fluconazole. Some beta-lactams have good or at least adequate oral bioavailability when dosed appropriately. Some life-threatening infections, such as meningitis or endocarditis, should not be treated with oral antimicrobials.
However, many other commonly encountered infections – including community-acquired pneumonia, skin and soft tissue infections, and urinary tract infections – are good candidates for either initial empiric or conversion to oral antimicrobial therapy to complete a course. Microbiologist, infectious disease specialist and clinical pharmacist (if available) can often assist when making decisions regarding the use or transition to oral antimicrobials.
-
Name as many benefits as you can of switching from IV to oral antimicrobial therapy.
-
You might have thought of:
- decreasing costs
- facilitating discharge
- avoiding complications associated with indwelling intravenous catheters, including infection and clots.
-
What factors determine whether a patient is a candidate for a switch from IV to oral?
-
You might have suggested that the patient can be switched to oral antimicrobial therapy if:
- they are eating or can tolerate food
- they do not have any condition that affects their ability to absorb antimicrobials administered orally
- their condition will respond to treatment with an antimicrobial that is orally bioavailable.
Patients with endocarditis or meningitis should not be switched to oral antimicrobials.
Frequency of dosing
