Oral or intravenous antibiotics

Welcome to the Australian Prescriber Podcast. The Australian Prescriber, independent, peer-reviewed, and free.

I'm Dhineli Perera, your host for this episode, and it's a pleasure to be speaking to Dr Minyon Avent. Minyon is an advanced pharmacist at the Queensland Statewide Antimicrobial Stewardship Program. Minyon and her team write about what needs to be considered when choosing between oral or intravenous antibiotics. Minyon, welcome to the program.

Thank you Dhineli, it's good to be here.

Minyon, can you start by telling us, from your perspective, why you think there is a perception out there in hospitals, that intravenous antibiotics will always work better than oral?

I think that's sort of based on a long tradition and culture of, if a patient is admitted to a hospital, then they warrant an intravenous line. In other words, they're sick enough to get a line inserted to receive fluids, and then whatever other medications they would need. And so antibiotics would probably be one of the considerations that the medical team will have a look at.

Right, so you're saying that the perceptions is all around the idea that, if they're sick enough to come to hospital, then that means they're sick enough to warrant a need for intravenous antibiotics, and that they will work better just because they are for more severe conditions. Would that be right?

Yes, that is correct.

And so, when are intravenous antibiotics actually recommended?

Yes. So basically, as you mentioned Dhineli, it's more for the severe infections, particularly more the life-threatening infections such as sepsis, also for your deep-seated infections such as your bone and joint infections, and infections associated with infective endocarditis. And then you also think of your immune-compromised patients, and then in those patients you probably want to start off with intravenous antibiotics, to ensure that they have sufficient concentrations in their bloodstream. So it's really more for your sicker patients, and the patients where you're worried about the antibiotic reaching the site of infection.

Okay. So do we actually overuse intravenous antibiotics in reality?

Well, in reality I think in Australia we overuse antibiotics in general, and certainly we do have one of the higher prescribing rates of antibiotics, when you compare us to other developed countries in the world. So in Australia we're fortunate to have surveys, such as the National Antimicrobial Survey, which is commonly known or abbreviated to NAPS, and these results are published in the Australian Commission for Safety and Quality in Healthcare. And basically, the findings of doing these surveys for many years now, is that between 20 to 30% of these antibiotics are used inappropriately, or not prescribed according to guidelines. And that's true both for intravenous and oral antibiotics.

I would say for intravenous antibiotics, one of the main things probably, is that maybe the antibiotic wasn't indicated in the first place. So in other words, the patient could've been started on an oral antibiotic, or for example, the duration is prolonged. So we know, particularly for conditions such as surgical prophylaxis, where you really only need to give one dose at the most 24 hours, there are cases where there is a prolonged duration of prescribing, particularly for a certain groups.

Okay. So you've touched on the bioavailability of oral antibiotics, but what are the real advantages of using oral antibiotics over intravenous in the first place? Why is it often better for the patient to use oral options?

So in order to receive an intravenous antibiotic, for the most part the patient would have to be admitted to the hospital. There are some conditions where these medications can be given out in the community, but that has to be in an appropriate setting, and then the patient would also need a cannula. So cannulas are not without complications. They can cause infections in their own right, and they do have complications such as infiltration, which requires the removal of the line. And for the patient as well, it means that they're less mobile if they've got an intravenous line, or they're hooked up to chair drip. And if they don't have an intravenous line in and they're in a hospital, then in many cases they are able to go home sooner, providing they're clinically stable.

So I think it does have many advantages for patients, and we've been working with paediatric patients and doing an IV to oral switch program. And certainly, that's one of the things parents are keen to do is to get their children home as soon as possible.

Okay. So with the term bioavailability, could you give us a quick refresher on what that's actually talking about?

Yeah, so really in simple terms, it's the fraction of administered drug that reaches the systemic circulation. So for an intravenous drug, the bioavailability would be 100%, but for oral antibiotics they test it to see what percentage reaches systemic circulation, and certain drugs have very good bioavailability for antibiotics. And basically when you change them from an intravenous to an oral formulation, you don't even have to adjust the dose. Some drugs you do have to adjust doses, and then some drugs aren't suitable or can't be given via oral route, and in many of those cases the formulation isn't available, you wouldn't be able to buy that drug.

So where would be the most reliable and accessible sources of information on the bioavailability of antibiotics? I guess for physicians and health professionals that are having to think on their feet, where should they go to find out?

We're very fortunate in Australia that we do have national guidelines, called the Therapeutic Guidelines, so that's widely available and accessible to anybody who has that subscription. So that's one source, and that will be the one I would recommend as the go to. And the reason why I say that, because often when you switch from an IV to an oral route, it might not necessarily be the same antibiotic that you're going to use, so the guidelines would guide you through about how to deescalate the patient's therapy, or what's the best oral medication to start for certain conditions.

And there's also the Australian Medicines Handbook that many people have access to as well, and in there when you look up the medication, you will be able to see if it's available as an oral formulation and what the bioavailability and recommendations are. So that's a resource that's independent of any pharmaceutical company, and it's put together by pharmacists with expert consultants from medical staff throughout the country.

Great, so Therapeutic Guidelines and the AMH would be your two recommendations for information sources-

Yes, I think-

... on the bioavailability?

I think particularly for people working in the community, because they don't always have access to some of the resources that we have in a hospital setting.

Yes, of course. And is there any good-quality evidence to say that a shorter course of intravenous antibiotics have similarly good outcomes for patients, and if so, in what indications would that be applicable for?

So there are a number of studies, and particularly more so in the recent years, where there's good evidence to show that courses can be administered for shorter durations. And I think overall, particularly in Australia, we seem to be leading the way where we do, for the most part, prescribe fairly short courses of antibiotics for certain types of infections. So the infections where there's the best evidence for this is your community acquired pneumonias, your skin and soft tissue infections, and some other respiratory conditions such as your chronic lung disease, exacerbations of chronic lung disease, some urinary tract infections for example, and intra-abdominal infections.

So that's shorter courses of intravenous, or just shorter courses of antibiotics altogether?

It's shorter courses in general, but the Therapeutic Guidelines, the most recent version which came out last year, has a lot more guidance about when to de-escalate from an intravenous to an oral formulation, and also quite good guidelines about when you can choose an oral formulation as opposed to an intravenous formulation when you don't need to start a patient on an intravenous antibiotic. There's a lot of information in the new Therapeutic Guidelines, and that's one of the sections that they've done a really good job on.

Yeah, excellent. And so it's great to know that that's been updated to have some really good guidance on de-escalation too.

Yeah, and particularly for paediatric patients as well. There's a lot more information for paediatric patients, which wasn't there in the past.

So I guess that leads me to my next question Minyon, does the guideline... or do the guidelines touch on the best way to know whether to switch to oral antibiotics or stop treatment altogether? I think you've sort of answered that, but does it sort of address that question specifically?

Yes, it does, it has some nice tables in there so basically for guidance, when to consider from switching from an intravenous route to an oral route. And the sort of most common things that you look for is, you really want a patient that's fairly stable from a hemodynamic perspective, you also want to obviously look for clinical improvement. Is the patient noted to have or documented clinical improvement in the underlying infectious disease condition, and resolving fever? So they don't have to be completely afebrile, but certainly they need to be trending down. They also have to have the ability to absorb the medication, so in other words not have any nausea and vomiting. And then also there has to be an oral formulation, as we talked about, that needs to be available.

I think for children, you also need to take the palatability of the medication into consideration, because certain antibiotics have a very bad taste. So we know that flucloxacillin and clindamycin, for example, have very bad tastes, and then often we would recommend another antibiotic that was more palatable.

Yes. And I guess also, I wanted to touch on the concept that, often we assume that patients need to have an oral tail to follow an intravenous course, but in some cases it actually is okay to complete the course with the intravenous course, and stop altogether. Has that been your experience as well, Minyon?

Yes. I mean, certainly you don't need to have an IV to oral, but really it's looking at how is the patient doing, have they responded, are they stable. And in some cases we just stop the intravenous, and we wouldn't consider putting them on an oral medication, as you've so rightly said.

Okay. And I guess finally Minyon, how does switching from intravenous to oral antibiotics help with tackling the bigger issue of antimicrobial resistance?

So really, when you look at antibiotic resistance, you look at the total use of antibiotics, and so if you can decrease the total use in whatever way, that would be of great assistance. So by reducing intravenous antibiotics and shortening the duration of the antibiotic course, this will contribute to less antibiotics being use, and it may reduce the development of antibiotic resistance. So I think it's really important…

Excellent

…to think about the appropriate use of antibiotics, because they are precious resources.

They certainly are, especially in these interesting times that we have ahead of us. Unfortunately, that's all we've got time for, for this episode. Thank you so much for joining us today, Minyon.

Thank you for inviting me, and it's been a great pleasure to speak to you.

The views of the hosts and guests on the podcast are their own, and may not represent Australian Prescriber or NPS MedicineWise. I'm Dhineli Perera, and thanks for joining us on the Australian Prescriber Podcast.