Lithium Levels

[hebel]

I had a few questions related to lithium levels:

1. For single qhs dosing, are you having the trough done 12h or 24h after the single dose? Some papers I've found have suggested 24h, and that 12h may overestimate the level by about 1.3x. For qhs dosing, the 12h is logistically much easier and this is the most common practice I see.


2. Let's say your patient misunderstands your instructions to obtain a trough level, and instead gets their labs drawn a few hours after their morning dose. Obviously that level will be elevated, but would you take action if that level was 1.9 but you know their troughs at that dose are usually 0.7?

Essentially, in the absence of symptoms do you interpret non-trough levels as void (even if getting into "toxic" ranges), because those ranges are based on trough levels?

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[ObsequiousAplomb]

I do instant release only, qhs dosing, and 12 hour levels. In the absence of clinical signs of toxicity, if it's high but drawn early then it's high because it's drawn early.

As long as they aren't experiencing symptoms of toxicity have them redo the lab at 12 hours to get an accurate reading.

 

[Merovinge]

I do instant release only, qhs dosing, and 12 hour levels. In the absence of clinical signs of toxicity, if it's high but drawn early then it's high because it's drawn early, .

As long as they aren't experiencing symptoms of toxicity have them redo the lab at 12 hours to get an accurate reading.

That's exactly how I prescribe it nearly all the time as well.

 

[Stagg737]

We prescribe the ER dosing frequently at our VA and trough levels are considered as close to the next dose as possible. Agree with OA that if they have elevated non-trough levels then you try and get a repeat level and monitor for signs of toxicity.

 

[Sikrouf]

I had a few questions related to lithium levels:

1. For single qhs dosing, are you having the trough done 12h or 24h after the single dose? Some papers I've found have suggested 24h, and that 12h may overestimate the level by about 1.3x. For qhs dosing, the 12h is logistically much easier and this is the most common practice I see.


2. Let's say your patient misunderstands your instructions to obtain a trough level, and instead gets their labs drawn a few hours after their morning dose. Obviously that level will be elevated, but would you take action if that level was 1.9 but you know their troughs at that dose are usually 0.7?

Essentially, in the absence of symptoms do you interpret non-trough levels as void (even if getting into "toxic" ranges), because those ranges are based on trough levels?

Hey

Could you give me a link to the papers you are refering in 1)?

 

[J ROD]

I tend to dose bid for that reason and try to have dosage the same to get a true trough in the AM. That way I can get a close to a true trough outpatient. Inpatient, I will sometimes do nightly if I have a psychotic patient with poor compliance.

 

[sloop]

If the level was 1.9 two hours after the dose but there were no symptoms, I would not tell them to discontinue lithium but I would basically insist that they get another level before they took their medication the following day. If they didn’t get that level I would stop it because, although the level is probably inaccurate, it is just too high to continue without a follow-up level that is reliable.

With regard to once a day dosing, I give instructions for a 12-hr for outpatients but this is mostly for practical reasons. It I’m doing once a day dosing, 90% of the time the dose is at night. I feel like telling someone that they must go to the lab at 8 PM or whatever is just a recipe for labs not actually getting done. In reality, I’m not gonna make an issue over when patients get their labs done on once a day dosing as long as it is somewhere between 12 and 24 hours. Yes, 12 hr levels may be a slight underestimate but they still help you avoid toxicity. Also, I tend to be somewhat aggressive and will target levels up to 1.0 in patients who haven’t responded to lower levels, which probably helps to mitigate the underestimation issue a bit.

 

[Sikrouf]

Another question i have is what lithium levels do you expect if youre giving IR bid
If you're giving IR bid im aware you re expected to be with .5 .8 mEq
But if you re giving it bid how do you manage ?

 

[ObsequiousAplomb]

I'm curious why people are giving ER or BID? Where I was trained it was emphasized as being safer and equally effective to do IR and once daily, most tolerable qhs. Do people who do ER or BID have a rationale I'm not aware of?

 

[Taddy Mason]

I'm curious why people are giving ER or BID? Where I was trained it was emphasized as being safer and equally effective to do IR and once daily, most tolerable qhs. Do people who do ER or BID have a rationale I'm not aware of?

Same. The only benefit of ER that I’m aware of is better tolerability in terms of side effects (namely GI). I’ve only run into this with one patient and the GI upset is pretty mild, inconsistent, hasn’t seemed to really bother him, or been an issue with compliance and he’s just stuck with the IR. The bid thing I’ve never understood given solid data demonstrating increased risk/incidence of nephrotoxicity and compliance issues that come with pretty much any med that needs to be taken more than once a day.

 

[mistafab]

They give the ER twice a day to reduce compliance.

 

[brazilianpsych]

I also always used Lithium only at qhs to reduce side effects and increase compliance. Do not see any point in doing it BID to be honest.

Between IR and ER, sometimes I would start with IR and change if the patient had GI upset or simply start the ER. Always seemed that the GI upset was a little reduced with the ER.

 

[Merovinge]

I also always used Lithium only at qhs to reduce side effects and increase compliance. Do not see any point in doing it BID to be honest.

Between IR and ER, sometimes I would start with IR and change if the patient had GI upset or simply start the ER. Always seemed that the GI upset was a little reduced with the ER.

This is one of those areas where I saw a lot of BID dosing by excellent psychiatrists as a resident. Since being on SDN and reading the articles previously linked about the tolerability and lower renal SE on daily dosing have entirely shifted my practice.

To answer OA above, the reason people use BID I presume is because that is how they learned. This is often the answer in medicine, but certainly one to push away form.

 

[Stagg737]

With regard to once a day dosing, I give instructions for a 12-hr for outpatients but this is mostly for practical reasons. It I’m doing once a day dosing, 90% of the time the dose is at night. I feel like telling someone that they must go to the lab at 8 PM or whatever is just a recipe for labs not actually getting done. In reality, I’m not gonna make an issue over when patients get their labs done on once a day dosing as long as it is somewhere between 12 and 24 hours.

Why not just have them go in the afternoon or after work if they work normal hours? If they take it between 9-10pm and they get the lab drawn from 4-6pm it's close enough that I'd just look at it as if it were the trough level. Any reason for the 12 hour preference or do you not care as long as it's after 12 hours?

 

[sloop]

Why not just have them go in the afternoon or after work if they work normal hours? If they take it between 9-10pm and they get the lab drawn from 4-6pm it's close enough that I'd just look at it as if it were the trough level. Any reason for the 12 hour preference or do you not care as long as it's after 12 hours?

They could go in in the afternoon. I guess my point is more the latter. I just don’t really care when they go as long as the get it. My experience has been that if I ask patients to get the level at 12 hrs, which usually winds up being in the morning, many of them will wind up forgetting initially but then running to the lab in the afternoon some time. If I tell them to get a 24 hr, they often forget and then wind up taking the nighttime dose, and sometimes the same thing happens the next day.

Frankly, I’m mostly getting the levels to make sure they’re not very high. The majority of the time, people are not going to be in a situation where their level is going to be high enough that I would discontinue lithium at 12 hours but low enough that I would be unconcerned at 24. While this can certainly happen on occasion, I think that the 12 hr level is more likely to be modestly high rather than very high (in which case they’re probably high at 24 hrs, too). If they’re modestly high, I can just tell them to get a repeat level where I’m more stringent that it must be taken at 24 hrs. For the vast majority of patients, though, I prefer to just give them the latitude about when to get the lab drawn.

I just think that patients are more likely to get a lab done when you tell them “just go get your lab drawn on X date during normal business hours and before you take your nightly meds” rather than if you tell them “please get this lab drawn at X time.”

But I agree that 24 hour is probably most ideal.