As per the subject, can anyone answer this? Having a real b%#~h of an admission in tertiary, with a tonne of issues with the antibiotics (wrong doses, missed doses) that’s included 2 high troughs at 18 hours post once daily tobramycin infusion. In eleven years and about 50 courses of IVs, and bar a really insane 4 (also at tertiary) last year that was disproven, she has never, ever had a high trough. The problem is that the initial high of 2 on day two fell to just 0.6 ten hours later, which from my limited understanding isn’t possible and therefore the initial level was likely erroneous (and 2 other patients in the last 2 weeks have had the exact same experience), but a day 12 trough came back as 1.1 yesterday resulting in the tobi being discontinued, primarily due to already being on a reduced dose after the day 2 reading and not wanting to reduce it further - we’d virtually be at the point where the dose is no longer therapeutic, so it’s pointless. That level has fallen to 0.4 at the equivalent post dose trough timing today, and I just really want to know/find out whether that is a plausible decrease in serum concentration levels in light of the nonsense one we had last week.
So, any takers? My normal resources are drawing a complete blank on this one. I know the dose she’s been on if anyone can find an equation/reference chart/whatever that will solve this for me. I know the half-life of tobi is 3 hours with normal kidney function, but that on it’s own doesn’t help me with the serum decline, and I’m guessing that there must be an established average elimination rate to have decided when peak/trough sampling should be carried out. There’s been a suggestion that they may say she should have a permanently reduced dosing schedule going forward, which is absolutely fine if it’s appropriate, but I don’t know if it’s appropriate or not without understanding the numbers a bit more and the relationships here are...terse.
I would love to be able to help you as you and little un are certainly going through it. Unfortunately I have never been tested for peaks and troughs of serum absorbtion when having IV. With non cf they tend to bing the drug into us and wait to see if the sputum changes and we feel better. I will be interested to hear if any non cf bronchs have had this sophisticated level of monitoring during IV but I doubt it. This doesn't help you of course. Please let us know what happens. Thinking about you both.
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That’s...well, I was going to say ‘interesting’ Littlepom, but my understanding is that serum concentration should be monitored in ALL populations with the use of any aminoglycoside regardless of underlying diagnosis or site of infection. Which makes it less interesting and more worrying, tbh. This is from the current BNF entry on Tobramycin:
“Serum concentrations
Serum concentration monitoring avoids both excessive and subtherapeutic concentrations thus preventing toxicity and ensuring efficacy.
Serum-aminoglycoside concentrations should be measured in all patients receiving parenteral aminoglycosides and must be determined in obesity, if high doses are being given and in cystic fibrosis.
In adults
Serum aminoglycoside concentrations must be determined in the elderly.
In patients with normal renal function, aminoglycoside concentrations should be measured after 3 or 4 doses of a multiple daily dose regimen and after a dose change.
For multiple daily dose regimens, blood samples should be taken approximately 1 hour after intramuscular or intravenous administration (‘peak’ concentration) and also just before the next dose (‘trough’ concentration). If the pre-dose (‘trough’) concentration is high, the interval between doses must be increased. If the post-dose (‘peak’) concentration is high, the dose must be decreased.
For once daily dose regimens, consult local guidelines on serum concentration monitoring.
With intramuscular use or intravenous use in adults
One-hour (‘peak’) serum concentration should not exceed 10 mg/litre; pre-dose (‘trough’) concentration should be less than 2 mg/litre.”
I’m not entirely sure what the difference is between should and must - either it needs monitoring or it doesn’t. Nephrotoxicity and ototoxicity don’t care why your lungs are crap, or if they’re even crap at all 🤷♂️ Paeds are always more cautious than adult care, it’s a universal constant, but the only discernible difference with use in cf is the dosing: patients wcf require higher doses to achieve therapeutic serum concentration as a result of the way their bodies process drugs. In paeds that equates to 10mg per kg of body weight in a cf child with normal renal function versus 7mg per kg for a non cf child. There’s a similar difference in the adult dosing.
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Can you get clarification from the consultant as to whether it needs monitoring or not and whether it levels meant that it had to be stopped? I have not so far had an IV drug that needs monitoring as I have only needed IV 3 times in my life so am not in a position to help you on this. It is awful when we can't get clarification from those who are supposed to know what they are doing.
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Except, from everything I know, if you’ve had IV tobi then they should definitely be checking your levels regardless. Unless they’re screening you and you weren’t aware? They do U&Es at the same time to check the kidneys, so if they’re doing bloods early doors into a course, that could be the case.
The cf forums are an absolute pile of pants and have been for years, unfortunately - that’s how I ended up here in the first place. They were great prior to the rebrand of the Cf trust about 5 years ago, a bit judgemental at times like any forum, but a really good resource with parents/carers posting several times a day and the adult patient board always busy. Last time I went to visit about a year ago, there’d been one post on the carers board in over a year and probably only a dozen in the same period in the adults. So it looks like you lucky guys are it for us now 😂
The situation here is untenable and has been for a long time, which is partly why we’re moving on the 24th, but the last place I really wanted to be two weeks before a 250 mile move is tertiary when they could have intervened weeks ago (and were asked to) but chose not to. Littleun is missing all the end of year stuff in school, and a lot of the leavers things seeing as she’s year 6, which just feels completely unnecessary. I effectively ‘gave up’ about a week in and have literally just been trying to get through it without completely losing my rag at the team and telling them exactly what I think, but everything I say goes in one ear and out the other. It’s literally a case of: yes, but she has more energy. Me: but she doesn’t. Them: but she’s eating better. Me: no, she’s not, you’ve got her on 40mg pred and she’s eating less than ever - your own scales show she’s losing weight! 😳🤦♂️
It’s speciality rounds this morning, so I’ll wait and see how it goes, but they’re planning to discharge her tomorrow regardless: I’m not entirely sure of the benefit of staying in on one antibiotic for another 24 hours when she won’t even have had a full course of it by tomorrow at any rate. Unless something amazing has happened over the weekend, her fev1 is still in her boots and 20% less than her well baseline, and although she is symptomatically improved from admission, she’s still clearing manky stuff in minor quantities: I live to be proven wrong, but if we’re not back at square one (for a third time) within a fortnight, I’ll be amazed.
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Oh dear it is terrible for you. Of course, cf has it’s own complexities which I have no experience of. It is a pity that they don’t listen to you as you know her best. It must be so difficult to keep your cool with them. Maybe as you are leaving saying what you think might not be so bad for them and very cathartic for you 😖.
I absolutely agree that if they are not going to give her a full course there hardly seems any point to wasting time for an extra night in the hospital. You may as well knock it on the head and let her do the end of term stuff that she can cope with. It is horrible to be left out - I remember.
Your experience is an eye opener for me because we non cf s assume that cf care is so good compared to ours and that the whole patient to patient support system is so much better. Not so it seems.
What you are saying about drugs and monitoring hi lights the discrimination between cf and non cf bronch in the NHS. For instance, we can have tobramycin nebulised but not tobi, which is a different form and deemed too expensive. I have never been offered tobramycin IV ( although this may be due to my needs). Meropenem and tazocin don’t require monitoring ( they say) It has been suggested that I have IV colomycin which they may monitor for toxicity, not for absorbtion and can you believe it, some centres still give bronchs nasty toxic old fashioned gentamycin IV which needs testing every 48 hours. I have escaped that one.
I do hope that when you move you transfer to a better centre - maybe at a big teaching hospital. Do keep us up to date. I am only sorry that my knowledge and experience of cf isn’t sufficient to be of much use to you but I can empathise as a person who knows far more about her own condition than many medics and other associated medical ‘practitioners’ whom I knock heads with.
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Just a thought. Might there be someone on one of the cf forums who has more experience of this and can duscuss it in depth with you.
Hi Charlie G, wish I could help but seems i cant even read it properly never mind undestand it ha! I hope that somebody who knows the complexity of these things can advise you. I wish you both well x
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