therapeutic drug monitoring

[BabyPsychDoc]

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Hey, guys

I am doing a literature review of lithium levels monitoring. So far, I have not been able to identify any evidence-based papers that would justify routine quarterly blood tests (which is what we do in the UK - do you do things differently in respect to this issue?). Are the "senior and reputed" 😀 members of this forum aware of any? (OK, replies from junior and not so reputed members are also welcome, so long as they are supported by PubMed links )

Also, in my PubMed travels I have stumbled upon this article http://www.ncbi.nlm.nih.gov/pubmed/...nkpos=3&log$=relatedarticles&logdbfrom=pubmed

Sounds like a proposal to monitor serum levels of antidepressants, too. 😱 To me, the idea does not seem particularly sound from the clinical point of view, but I wonder what others think.

Thanks.

 

[Anasazi23]

I just did a sort of lit review after a lithium toxicity malpractice case. I didn't come across any evidence-based guidelines for quarterly monitoring.

The APA lists, in their practice guidelines, the lithium monitoring suggestions. As far as statistical evidence base, however, we might need to clarify your question. In other words, what hypothesis would there be that would suggest that quarterly monitoring would be required? Increased incidence of toxicity cases if done less frequently, for example? Something about the pharmacodynamics or pharmacokinetics of the drug after taking it for three months that would necessitate its monitoring at that frequency?

 

[BabyPsychDoc]

I just did a sort of lit review after a lithium toxicity malpractice case. I didn't come across any evidence-based guidelines for quarterly monitoring.

The APA lists, in their practice guidelines, the lithium monitoring suggestions. As far as statistical evidence base, however, we might need to clarify your question. In other words, what hypothesis would there be that would suggest that quarterly monitoring would be required? Increased incidence of toxicity cases if done less frequently, for example? Something about the pharmacodynamics or pharmacokinetics of the drug after taking it for three months that would necessitate its monitoring at that frequency?

Thanks, Sazi. The British National Formulary (kind of PDR in the UK) states that Li levels should be checked routinely every 3 months. This suggestion has been adopted as standard practice over here, and people get very excited (not in the good sense) if you do not do this (obviously, since you are not following the generally accepted standard of practice, you also risk your medical licence/legal suit - yes, British docs get sued, too).

Now, I spent the whole day on the internet yesterday and I could not find ANYTHING, anything at all that would provide rationale to such frequent monitoring in otherwise asymptomatic patients with no intercurrent illness and not on any medication known to affect Li levels/Li toxicity. There is nothing about pharmacokinetics/pharmacodynamics of Li that would justify such monitoring; there is no hard evidence about increased Li toxicity if monitored less frequently; and it is known that in fact Li levels do not have 100% correlation with clinical picture of Li toxicity.

It looks like the NHS is wasting tons of money on this. So, I am thinking of trying to make an evidence-based case AGAINST routine Li levels monitoring.

Thanks for the link, too.

 

[Anasazi23]

Thanks, Sazi. The British National Formulary (kind of PDR in the UK) states that Li levels should be checked routinely every 3 months. This suggestion has been adopted as standard practice over here, and people get very excited (not in the good sense) if you do not do this (obviously, since you are not following the generally accepted standard of practice, you also risk your medical licence/legal suit - yes, British docs get sued, too).

Now, I spent the whole day on the internet yesterday and I could not find ANYTHING, anything at all that would provide rationale to such frequent monitoring in otherwise asymptomatic patients with no intercurrent illness and not on any medication known to affect Li levels/Li toxicity. There is nothing about pharmacokinetics/pharmacodynamics of Li that would justify such monitoring; there is no hard evidence about increased Li toxicity if monitored less frequently; and it is known that in fact Li levels do not have 100% correlation with clinical picture of Li toxicity.

It looks like the NHS is wasting tons of money on this. So, I am thinking of trying to make an evidence-based case AGAINST routine Li levels monitoring.

Thanks for the link, too.

I think the inherent problem is that if something changes in the specific physioology of the patient - for whatever reason, lithium levels could change, and develop into toxicity. Renal clearance changes as we age, heavy exercise can result in renal clearance changes, etc. The forensic case I recently reviewed, in which a woman developed severe toxicity for no discernable reason after having taken Li since the 70's, makes me reluctant to say that therapeutic monitoring should not take place if there is perceived stability. I, as I'm sure you do, treat the patient - not the numbers. But, I think a q 6 month minimum isn't that unreasonable.

 

[BabyPsychDoc]

I think the inherent problem is that if something changes in the specific physioology of the patient - for whatever reason, lithium levels could change, and develop into toxicity. Renal clearance changes as we age, heavy exercise can result in renal clearance changes, etc. The forensic case I recently reviewed, in which a woman developed severe toxicity for no discernable reason after having taken Li since the 70's, makes me reluctant to say that therapeutic monitoring should not take place if there is perceived stability. I, as I'm sure you do, treat the patient - not the numbers. But, I think a q 6 month minimum isn't that unreasonable.

I hear what you are saying, but would not it be better to share the responsibility of Li levels monitoring with the patient's PCP, who could do the test if the patient developes an acute intercurrent illness or started on a additional medication that may potentially affect Li pharmacokinetics? Or, raising awareness of Li toxicity and the importance of clinical monitoring among PCPs, so that when Jane pops in to see her doc for whatever reason, the PCP quickly screens for symptoms of Li toxicity?

There was an interesting study done at Maudsley hospital in London in 1990s. They found that psychiatrists there adhered poorly to the BNF guidelines, which by itself was not a great surprise. The interesting bit was that the more senior the psychiatrist was, the less frequently s/he monitored Li levels - yet, their patients had the fewest "out-of-range" concentrations. Just goes to support "treating the patient, not the number" theory.

 

[Anasazi23]

I hear what you are saying, but would not it be better to share the responsibility of Li levels monitoring with the patient's PCP, who could do the test if the patient developes an acute intercurrent illness or started on a additional medication that may potentially affect Li pharmacokinetics? Or, raising awareness of Li toxicity and the importance of clinical monitoring among PCPs, so that when Jane pops in to see her doc for whatever reason, the PCP quickly screens for symptoms of Li toxicity?

I routinely partner my patient's lithium levels with their PCP visits. It's a great way to do it and get updates on their medical status concurrently.

I sort of know where you're going with this. And on a strictly scientific and more importantly, practical level, I can nearly agree. But, (and again I think I'm becoming more paranoid as I continue my forensics fellowship), the possibility of an acute physiological change that leads to either a decreased clearance or increased clearance, should it not be on record, makes your case that much harder to defend in the unlikely event that some unforseen or untoward event does occur.

Further, by not having a consistent "baseline" comparison, getting a random Li level, say, 2 years after not having checked it gives you relatively little information when a patient presents with either an exacerbation of their mood lability or conversely, when whey become physically ill or toxic. By knowing where a patient "lives" in their therapeutic range of Li, we can much easier make adjustments.

Also, from a purely practical standpoint - would you not recommend renal and thyroid function tests at least q year ? Why not piggyback the Li on with that for the hell of it?