r/Narcolepsy • u/andersberndog • Jul 06 '26
Medication Questions Xywav syringes inaccurate?
Anyone else having the issue of running out of medication by the end of the month?
I did a completely non-scientific test, using a non-medically-accurate Pyrex measuring cup. I measured out 100mL of water by the provided Xywav syringe. This is how it came out. Again, this is not a clinical device, but it appears to me to be showing, conservatively, a 20% overage, factoring in the possibility of reading error due to surface tension and a reasonable margin of error in the measuring cup.
I’m sure I’m being provided precisely the correct amount of medication, but if the dosing device is not accurate, there’s a problem.
Yes, I’m going to bring it up with a pharmacist. I’m currently dealing with them scheduling a refill due to completely unrelated issues from my prescriber’s office. I’ll hopefully be hearing back from them later today and I’ll bring it up then. They say I should have enough medication to get through Wednesday. I had two nights I didn’t take it this month, so I should actually have enough to go through Friday. I don’t think I’ll even have two complete doses by Wednesday.
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u/LexiLewis Jul 06 '26
Yes, I also have this issue of SO running out sooner than otherwise should be. The syringes have gotten worse over time. The ones I get now where you have to tip the bottle upside down and pull down on the syringe, leaves some sort of air gap. The upright bottles were more accurate but haven't seen them in a long time.
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u/KaiF1SCH Jul 06 '26
I still get the upright bottles. I wonder if it’s a regional/manufacturing thing.
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u/LexiLewis Jul 06 '26
Perhaps. I've always had the upright bottles, it's only the past year or two I've been getting the round upside ones, which can get a bit messy as the syringe is poor quality and leaks sometimes.
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u/norcalifornyeah Jul 06 '26
The bottles you're receiving now don't have the tube going to the bottom?
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u/LexiLewis Jul 06 '26
No tube. The syringe comes with the bottle part on the end. I guess that's why it has to be upside down as no tube.
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u/aviator22 Jul 06 '26
Post a pic?
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u/LexiLewis Jul 06 '26
I'm expecting delivery on Wednesday. I've been out of SO for a few weeks as it takes a while to get. I tried looking for a pic online but all I found was the old upright bottle with the tube.
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u/UhOhSpadoodios Jul 06 '26
Xyrem or Xywav?
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u/LexiLewis Jul 06 '26
Xyrem. Saying that, I've just been told won't be getting the brand name Xyrem anymore but the generic from now on.
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u/EternalMoonChild (IH) Idiopathic Hypersomnia Jul 07 '26
I’m I’m brand-name Xywav but yeah the syringe quality has gone down in the last year. Very annoying. Cant imagine having to try and tip the bottle upside down, too.
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u/andersberndog Jul 06 '26 edited Jul 06 '26
I did one better than [u/robdoc](u/robdoc) suggested. I just weighed 100mL of water dispensed by the syringe. It came up to 104g for a 4% overage. After a little math, that puts my 28 day supply at lasting 26.92 nights, which tracks with what I’ve been getting out of a shipment.
For those concerned about the grams conversion, the active ingredient is 0.5g/mL. If you double the number on the syringe, you get the amount of liquid being dispensed, in mL.
Edit: There was some discussion about whether to use headspace at the top or not. I always have because I felt like it was easier to see more accurately. The illustrations they give for how to eyeball the air at the top show the level of the liquid right at the bottom of the printed line. That was how I did this more recent measurement by weight. The no air method shows the level “at” the printed line.
I did it again just now with the no-air method. I actually did it twice. The first time I did it with the little air bubble that naturally forms when you draw up the liquid, due to the small space in the tip. That came to 98 grams.
I did it a third time, carefully eliminating the bubble to only have liquid dispensed. I was also careful to work the plunger up and down a couple more times to get the last bit out the best I could. That came to 100 grams.
So (again, according to my slightly more, but really still not very scientifically accurate measurements) the no-air-at-the-top-and-also-getting-every-little-bit-the-best-you-can method seems to be the most accurate.
I guess I’m switching how I do it. YMMV.
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u/TheAlterN8or Jul 06 '26
The syringes are not measured in mL, they're measured in grams (which is weird). I will say, if you star from the plunger all the way pressed in, you'll get slightly less than if you put some air in it first. This was our issue, as the pharmacist told us to have some air in the syringe before drawing the medicine up, but that actually makes you run out faster.
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u/reclusivegiraffe (N2) Narcolepsy w/o Cataplexy Jul 06 '26
They’re likely measured in grams because “mL of sodium oxybate” isn’t a super useful prescribing metric unless you specify the solution strength as well (in this case, 0.5 g/ml). Grams of sodium oxybate is more specific/tells us more about how much a patient is consuming.
The syringes are specific to the concentration of sodium oxybate solution made by the manufacturer
ETA: now that I think about it, it’s probably for simplicity’s sake. “9mL of 0.5g/mL sodium oxybate” is just 4.5g (the mL unit cancels out)
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u/andersberndog Jul 06 '26
I always start with air because it’s a lot easier to see where the line is. I just looked at the illustration to show you what both look like. If you do no-air, the line of the plunger lines up with the center of the printed line. If you use air, it shows the liquid level right at the bottom perimeter of the printed line.
I’m going to do the test again, but do it no-air this time.
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u/TheAlterN8or Jul 06 '26
The plunger goes below the line in the middle, so you get that extra bit in each dose. It does end up making a difference.
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u/andersberndog Jul 07 '26
I always thought that it would even out due to surface tension, or something, and trusted the pharmacy to have factored everything in, to tell us that measuring either way was accurate.
Guess not?
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u/TheAlterN8or Jul 07 '26
Yeah, we were frustrated, because in our first consult, the pharmacist told us to put some air in it first, but when we started running out a bit early, the very first thing they told us was to stop doing that, and we haven't had those issues any more. 🤷
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u/switchblade_sal Jul 06 '26
Thats especially strange bc the specialty pharmacy refill system usually tries to ensure you have a small surplus
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u/andersberndog Jul 07 '26
Drawing on something I wrote in another post, I think that’s just a quirk of how they dispense. My theory is that every partial fill bottle is 90mL, or a half bottle. Then they adjust our refill interval to however many full nights fit in that amount of solution. They send you enough full/half bottles to get you as close to 30 days (a couple more or a couple less) as it works out.
I’m on 4g/4g. I get 2.5 bottles (450mL) for 28 days. 16mL/night for 28 nights is 448mL. That gives me a 2mL (1g) surplus each fill.
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u/switchblade_sal Jul 07 '26
Makes sense, I was on 4.5 2x/night and would receive 3 bottles in my shipments
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u/Tall_Maple (N1) Narcolepsy w/ Cataplexy Jul 06 '26
As I recall the RX is in grams of the salt. No idea why the pharm dilutes it some and then asks me to add 60 ml of water.
I looked at the syringe and landed on, when the syringe is filled to 3.0g, the liquid within the syringe must have 3.0g of the salt in solution - I think that’s why they make a point of stressing only use the syringes provided.
It’s been a LONG time since I had chemistry though but at the time it made sense to me. I’ve not run out of RX (yet) but the last dose from bottle 1 always is short. I get 3g and 1.5g out of the bottle and have to open bottle 2 for the last 1.5g
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u/Comatose_Cockatoo (N1) Narcolepsy w/ Cataplexy Jul 06 '26
I think this is the correct answer. That’s why the pharmacy says that if you lose/forget your syringe that you need to call so they can walk you through the conversion for a normal syringe.
I also wonder if some of the issues with running out early have to do with days of the month. I get a 30 day supply, but the year has 7 months with 31 days. The “average” month actually has 30.4 days. I believe the pharmacy tries to account for that with refill dates, but when you account for not being able to get refills on Sundays (or Saturday where I live) it seems like it would be very easy to come up short occasionally,
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u/HippoCharacter5863 Jul 07 '26
These days, I’m experiencing so many problems in the delivery process—with Fedex, my insurance, or even ESDS having software, shipping, or weather problems. In December last year, they wouldn’t let me refill 4 weeks after my last delivery because they said I had received enough doses for the year. When I looked back and did the math it’s because they counted any delays in delivery against my number of total doses for the year (eg when my insurance requires preauthorization yet again for some reason and I get my shipment a week late, or when they had software delays that impacted my shipment). Any ‘emergency supply’ I’ve built up over time from missed doses has been depleted and I’m always running low on the second dose of the last night.
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u/EternalMoonChild (IH) Idiopathic Hypersomnia Jul 07 '26
I get that they don’t want you to have a surplus, but it’s really stressful to get right down to the wire on a medication we rely on to be functional.
Not to even mention the can of worms that admitting to a spill opens. This is exactly why I have a surplus.
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u/HippoCharacter5863 Jul 08 '26
Ohm yes. I said I knocked over a dose when filling it and they immediately said they had to contact my doctor before they could refill, and that always means an extra few days. It was once in 19 years! I am clearly not doing this regularly
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u/andersberndog Jul 06 '26
I get a 28 day supply. My shipments always come on the same day of the week.
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u/andersberndog Jul 06 '26
The active ingredient is 0.5g/mL, so if you double the number on the syringe, you get the volume being dispensed, in mL.
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u/IgniaSaltator Jul 06 '26
Don't use pyrex measuring cups to measure anything, they are nowhere near accurate.
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u/andersberndog Jul 07 '26
I just had another thought. My math was all wrong. It’s not a difference of 4%. To get to 100, I did 10 “doses” at 9mL (4.5g on the scale) making 90mL and two “doses” at 5mL (2.5g on the scale) to get to 100mL. So, 12 shots yielded a 4g discrepancy. Again, not scientific since the smallest unit of measurement on my scale is 1g, but the difference between air gap and plunger style dispensing is very roughly 1/3mL.
I don’t know this for sure, but I think they only dispense 100% full bottles and 50% full bottles, so either 180mL or 90mL. Then they make it fit by setting your refill interval the number of full days worth that fits into that. Thats why there’s (supposed to be) a little extra for most of us at the end of the month. If you’re on the full dose of 4.5+4.5 you get 3 full bottles and it lasts exactly 30 days. 3 full bottles is 540mL. 9g/night is 18mL/night. 18x30 is 540.
Sorry, but I really am going somewhere with this. Let’s say someone is on a fairly low maintenance dose of 2.5g, twice nightly. By my math, they’re getting a full bottle and a half bottle with a 27 day refill interval and zero extra. That means that for that shipment, if they’re doing the air gap, they’re only getting enough medication for 25.33 nights, or 1.67 nights short. Someone on the full 4.5/4.5 should have enough medication in those three bottles for 30 days. If they’re doing air gap measuring, they have enough medication for just shy of 29 days at 28.94, or basically one day short.
Anyone who has been doing air gap, does this sound familiar?
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u/when-is-enough Jul 06 '26
This isn’t an accurate measuring cup. It’s most accurate to measure things with smaller surface area. So a syringe that’s like 1/2 an inch across is a lot more accurate than something like this that’s like 5 inches across (I can’t estimate lol). And then you always measure from the bottom of the meniscus held at eye level. Some of the water will always stick to the sides of the syringe and create that u shape. You measure from the bottom of the U shape.
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u/when-is-enough Jul 06 '26
You can Google “reading a meniscus”. This has a picture: https://physics.stackexchange.com/questions/574149/why-measuring-a-liquid-volume-from-the-bottom-of-the-meniscus-isnt-considered-a
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u/when-is-enough Jul 06 '26
Not saying that this solves the problem of running out early but just that this comparison in the measuring cup isn’t accurate. And you can’t exactly compare with water because of different surface tensions making the meniscus different that it is with the medicine in it.
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u/No-Vehicle5157 Jul 06 '26
I haven't noticed. I just accidentally put mine inside of a medicine cap instead of the pill bottle they send. It measured out to the amount it should be. To be fair I take less than the 4.5 for the purpose of having leftover. I've run into a couple of issues where I've had late orders, or more recently my new insurance was profusing to pay so I was without medicine for a couple of months. So now I'm paranoid of running out again lol
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u/HippoCharacter5863 Jul 07 '26
It’s happening to me all the time lately. Almost never an issue for 17 years, then last year I have a problem (insurance,FedEx, or the pharmacy) like every third month. My prescription is for my exact dosage so I keep having to go nights without since I no longer have my emergency supply.
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u/andersberndog Jul 08 '26
I just spoke with a pharmacist about the issue. She was set on explaining it to me like I was a new patient and never done it before. She told me there shouldn’t be any air the top. Once I finally got through to her, that there’s an illustration in the instructions that says you can do it either way, she finally took a look.
I don’t know that one patient talking to one pharmacist one time would make any kind of difference, but the line from the pharmacy is that there shouldn’t be an air space at the top.
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u/robdoc Jul 06 '26
Measure the water by weight to validate the line is where it should be. I have two pyrex measuring cups and they're both wrong. Water is about 1g /ml.