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Antimicrobial Key Considerations

Antimicrobial Pharmacist describes their role in OPAT
Hi, I’m Fiona, I’m an antimicrobial pharmacist for the OPAT service in Glasgow and my role is really to ensure safe, effective, appropriate antibiotics for OPAT patients. When patients get referred to OPAT, I think the most important thing is to find out what medicines they’re prescribed to ensure that any antibiotic plans we want to instigate are not going to interact and are not going to cause problems with what we want to achieve in the patient. So I am just making sure there are no drug-drug interactions and also having discussion of any drug food interactions or any supplements they might be taking, including homoeopathic medicines and herbal medicines and things like that as well.
But, really, just to ensure that it’s not going to cause issues with any plans we want to instigate. So sometimes we choose drugs within the antibiotic plan that require therapeutic drug monitoring, just to ensure the ongoing safety of these drugs in patients. So in the hospital setting, we might choose something like a glycopeptide, for example, like vancomycin. That’s not really appropriate to use in the outpatient setting because we have to have multiple daily dosing, and we tend to change that to a drug called teicoplanin, another glycopeptide, but we use the advantage of a long half-life to enable us to use to either a daily or three times a week dosing.
But we still need to do levels to ensure that we’re achieving a safe level in a patient that’s effective as well for treating infection. So it’s important to individualise a dose, and ensure that we can take levels at an appropriate time, and try and get those type of levels back in a timely manner, and try and interpret them for that individual patient. And the other drugs we do that for include amikacin, and we might use that for microbacterial infections. And, again, using an aminoglycosides in an outpatient setting we have to ensure that we do levels to ensure its safety, but also that we’re getting effective levels.
And I think that’s a really important role to play, and it just shows that we are achieving safe and effective use of these drugs in an outpatient setting, as we would equally in the hospital setting. So, obviously, when we choose any antibiotic for the outpatient setting for parental antibiotics, it’s desirable to give everything as a bolus because that is quick and easy for the patient either when they’re self-administering or to administer in the hospital. But it has to be quick for the patients, so we’re not tying them into the hospital for long periods of time. Obviously, that isn’t achievable for all drugs, and some drugs have to be given as an infusion.
And when we choose any drug with an infusion, we, again, try to choose something that’s got a short infusion– maybe up to a maximum of 30 minutes. But there are new devices out in the market, and through stability trials that we’re doing at the moment that we can actually maybe use certain drugs and administer them as continuous infusions over a 24-hour period. And that enables us to use drugs like flucloxacillin, which we haven’t used before in an outpatient setting because traditionally it’s a four times a day dosing, which isn’t really practical for outpatient use.
But the continuous infusion pumps that are now becoming available does mean that we could use this drug maybe for things like Staph Aureus Bacteremias, where it’s a desirable first-line option, and it gives us the opportunity to use it for these patients, and take a different group of patients into the OPAT service. I think it’s always important if we are trying to use anything outwith the standards product characteristics for a drug. For example, in continuous infusion, drugs we were using something like flucloxacillin continuous infusion that we do ensure that we’ve got good stability evidence and that’s through these trials that we can do to ensure the storage stability in different temperatures, and in the patient’s home environment as well.
So weekly, we have a virtual ward round which is attended by clinicians and myself, as pharmacists, and a nursing staff– special nursing staff in the team. And I think it’s just a really good example of a multidisciplinary team. We all bring something different to that team. Certainly, before the ward rounds I would tend to make sure I’ve looked at the patients renal function, hepatic function, and see if any trends are changing in that patient– look to see if we started any new medication out with the OPAT service. And just checking that actually things have been instigated as planned.
And then when we’re at the ward round we obviously discuss about any changes that happen to the patients– discuss anything that’s changed with the nursing staff. And I think that’s really important just to get an update on the patient, so that we know that they’re tolerating medication, and not having any issues with what we’ve instigated. So whenever we start planning an OPAT, we obviously tell the patient about any potential side effects they might have with medication. And that maybe some things that are a bit common to the drug, but also some maybe more rare side effects that they might experience.
And that’s just to make sure that they’ve got prior knowledge to this, but also that they have a familiarity with the team. They know they can phone up, and tell us about any issues they’re experiencing with the medication. And, of course, if they do experience any side effects, depending on the seriousness of those effects, it might be something that we can tailor the drug dose. We may have to stop the drug and change it to something else. And, of course, if it is something significant, we’ll make sure that we report that up through our national mechanisms. In the UK, we have the Yellow Card Scheme, so everything is reported back through that system if need be.
And, of course, we also record that through our own OPAT service, just for ongoing monitoring and any changes we may need to make. So as a antimicrobial pharmacist, I’m also involved in guideline development for the OPAT service. So I think it’s really important as a pharmacist to try and bring our knowledge of pharmacokinetics and pharmacodynamics to the choice of drug for different disease states because we can suggest how to optimise that drug in a particular infection. Do we need to achieve a high concentration, or are we looking for a continuous level in the body to achieve optimal levels for that drug?
But we can also bring knowledge on bioavailability, distribution, metabolism, and how the drug is actually cleared from the body. So that we can build in any dose changes that we might require for evading renal impairment or liver impairment for that drug. I also think it’s important just to also impact on any IVOST options, so if we have started to implement IV antibiotics, what would be the most appropriate oral antibiotics. And I think any choice of antibiotics we have for the OPAT guidelines, they have to mirror the same antimicrobial stewardship policies and prescribing that we have in hospital, and because we are accountable for that in an outpatient setting too.
So my responsibilities also includes just ensuring that any plan that we instigate also adheres to all our antimicrobial stewardship principles. So obviously just ensuring that we use narrow-spectrum antibiotics where possible, we de-escalate where possible, and we will IVOST when it’s appropriate for the patient, and we stop therapy at an appropriate time. I also think it’s really important that we’re able to justify our antibiotic use in OPAT and that we’re open to scrutiny by the organisation’s antimicrobial stewardship programme. And that’s why our OPAT service will regularly report back the antibiotic use and cost back to our stewardship committee. So, finally, as an antimicrobial pharmacist, I took the opportunity to train to become a nonmedical prescriber.
While it is not essential to my role in OPAT, I did think it would help expand my role, and I think it helps just make the whole process a bit slicker for patient care. It means I can help instigate plans prior to patient discharge, and I could change drugs if there was any drug interactions or intolerances in the patient. Whilst as I say it was not essential, I am aware that there are some pharmacists in other services where this is their main role, they are making plans and changing drugs on a fairly regular basis. And this is something we’d obviously like to emulate in other services.

The antimicrobial choice should be based on the principles contained in the local antimicrobial stewardship programme, taking into account:

  • The antimicrobial spectrum (narrow, specific to the organism & minimal potential for collateral damage).

  • Antimicrobial penetration and target site (good tissue concentration at the site of infection).

  • The antimicrobial’s side effect profile (minimal and well tolerated drug).

  • Antimicrobial drug–drug and drug–host interactions (no interactions).

  • Antimicrobial dose and dosing frequency (once daily or less frequent).

  • The antimicrobial’s mode of delivery (bolus).

  • Orally bioavailable antimicrobial alternatives.

  • The duration of antimicrobial therapy and criteria for stopping or switching.

Of particular importance is the need for antimicrobial agents (both parenteral and oral) used within OPAT programmes to be approved via an antimicrobial stewardship committee and, as necessary, hospital new medicine committees or equivalent. Evidence for their use in terms of clinical efficacy, safety and financial data should be evaluated.

Watch the full video with the OPAT AMT Pharmacist.

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OPAT: Outpatient Parenteral Antimicrobial Therapy

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