Venlafaxine plasma level

[Sikrouf]

Hello
Patient has venlafaxine 225mg in the morning
When shall i draw bloods? In the evening 12h post dose or just before the morning dose ?

Thank you

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[TexasPhysician]

Hello
Patient has venlafaxine 225mg in the morning
When shall i draw bloods? In the evening 12h post dose or just before the morning dose ?

Thank you

Why are you doing this?

 

[Sikrouf]

Long story short patient is 1) weird 2) without any improvements 3) without any side effects 4) with a "bypass" (not sure whats the type yet)

 

[robellis]

Long story short patient is 1) weird 2) without any improvements 3) without any side effects 4) with a "bypass" (not sure whats the type yet)

What’re you gonna do with the levels? I’m not aware of established evidence based Effexor levels? Are there?

 

[Mass Effect]

Long story short patient is 1) weird 2) without any improvements 3) without any side effects 4) with a "bypass" (not sure whats the type yet)

What do you mean the patient is "weird"? Why do you need levels? We don't get venlafaxine levels. If they don't improve, you switch to something else or in some cases, you may augment. When did they have bypass? Are they on ER formulation?

 

[notamindreader]

Long story short patient is 1) weird 2) without any improvements 3) without any side effects 4) with a "bypass" (not sure whats the type yet)

lol, this post is weird.

 

[brazilianpsych]

Just pick a random number and imagine that that number is the plasma level. Also imagine that there is no reference value. There you go!

 

[Sikrouf]

I thank you all for your input but i didn’t come here to be lectured on whether or not getting venlafaxine plasma levels is overall useless or not
Thats an issue we could discuss this for hours on end with i think a lot more nuance but again that wasnt the question at all

I would be very cautious about statements such as "we dont do X", the more you learn the more you realise things arent black or white especially in psychopharm

Ive found an answer anyway, thank you for your time

 

[robellis]

I thank you all for your input but i didn’t come here to be lectured on whether or not getting venlafaxine plasma levels is overall useless or not
Thats an issue we could discuss this for hours on end with i think a lot more nuance but again that wasnt the question at all

I would be very cautious about statements such as "we dont do X", the more you learn the more you realise things arent black or white especially in psychopharm

Ive found an answer anyway, thank you for your time

What’s the answer? If you know something we don’t we’d be happy to learn more..

 

[clozareal]

It's no less than 12 hours but ideally right before the next dose for venlafaxine and ODV (its active metabolite) plasma levels. The reference value where most will respond is when the ven+odv plasma level is between 195 and 400 ng/mL and risk of toxicity is when levels are over 800.

What’s the answer? If you know something we don’t we’d be happy to learn more..

Venlafaxine has a dose-response relationship for MDD. There's evidence that you can push up the venlafaxine dose above 375mg/day up to 600mg/day if plasma levels are low, and above those doses dopamine reuptake is also blocked in some patients. There's a recent study of this for desvenlafaxine as well.

This is probably related to p-glycoprotein, which kicks drugs like venlafaxine/desvenlafaxine (as well as other SSRI/SNRIs) out of the CNS rather than metabolization by CYP P450 enzymes in the liver (for venlafaxine it's CYP2D6 but for ODV it's UGT1A1 for ODV, a glucuronidation phase II pathway and not phase I/CYP P450 pathway, and one that doesn't come up on typical pharmacokinetic genetic tests).

The gene test for p-glycoprotein is probably the most useful genetic test as patients were 3 times more likely to remit from depression with an NNT=3. This was followed up by a second study for desvenlafaxine which suggests a dose-response relationship above 50mg up to 200mg whereas the PDR states that there's no evidence of more benefit above 50mg/day.

This is an even bigger deal if the patient is on another medication that is a strong p-glycoprotein inducer (most likely the case if pt isn't responding) or inhibitor. Really wish there was a way to get genetic testing for ABCB1 & ABCC1 in the US, which are the genes that code for p-glycoprotein.

 

[Mass Effect]

I thank you all for your input but i didn’t come here to be lectured on whether or not getting venlafaxine plasma levels is overall useless or not
Thats an issue we could discuss this for hours on end with i think a lot more nuance but again that wasnt the question at all

I would be very cautious about statements such as "we dont do X", the more you learn the more you realise things arent black or white especially in psychopharm

Ive found an answer anyway, thank you for your time

I think the first question you got was asking you why. Your response was that the the patient is weird and some other ambiguous stuff. We don't do this is a perfectly fair response as this is not standard. If you want to do it anyway due to special circumstances or whatever, go right ahead. But we don't typically do this and I think that needs to be said so that others reading this thread don't suddenly get the idea that everyone needs a V-level.

 

[Merovinge]

It's no less than 12 hours but ideally right before the next dose for venlafaxine and ODV (its active metabolite) plasma levels. The reference value where most will respond is when the ven+odv plasma level is between 195 and 400 ng/mL and risk of toxicity is when levels are over 800.



Venlafaxine has a dose-response relationship for MDD. There's evidence that you can push up the venlafaxine dose above 375mg/day up to 600mg/day if plasma levels are low, and above those doses dopamine reuptake is also blocked in some patients. There's a recent study of this for desvenlafaxine as well.

This is probably related to p-glycoprotein, which kicks drugs like venlafaxine/desvenlafaxine (as well as other SSRI/SNRIs) out of the CNS rather than metabolization by CYP P450 enzymes in the liver (for venlafaxine it's CYP2D6 but for ODV it's UGT1A1 for ODV, a glucuronidation phase II pathway and not phase I/CYP P450 pathway, and one that doesn't come up on typical pharmacokinetic genetic tests).

The gene test for p-glycoprotein is probably the most useful genetic test as patients were 3 times more likely to remit from depression with an NNT=3. This was followed up by a second study for desvenlafaxine which suggests a dose-response relationship above 50mg up to 200mg whereas the PDR states that there's no evidence of more benefit above 50mg/day.

This is an even bigger deal if the patient is on another medication that is a strong p-glycoprotein inducer (most likely the case if pt isn't responding) or inhibitor. Really wish there was a way to get genetic testing for ABCB1 & ABCC1 in the US, which are the genes that code for p-glycoprotein.

If you're worried the cause is a P-glycoprotein effect that is pumping the medication out of the CNS and can't access a gene test, why not just switch to a medication that is not effected by P-glycoprotein? Correct me if I'm wrong but I vaguely remember Cymbalta and Prozac of the SNRI and SSRI group are not moved by the P-glycoprotein system.

 

[clozareal]

If you're worried the cause is a P-glycoprotein effect that is pumping the medication out of the CNS and can't access a gene test, why not just switch to a medication that is not effected by P-glycoprotein? Correct me if I'm wrong but I vaguely remember Cymbalta and Prozac of the SNRI and SSRI group are not moved by the P-glycoprotein system.

Yep you can definitely do that.

 

[FlowRate]

In case anyone else was wondering if OP's 4th reason for looking at blood levels was relevant--a RYG Bypass does not seem to affect venlafaxine absorption according to this first-hit from googling the question.

Comparison of Bioavailability of Single-Dose Extended-Release Venlafaxine Capsules in Obese Patients Before and After Gastric Bypass Surgery - PubMed

This study suggests that RYGB does not significantly alter the amount of venlafaxine or its active metabolite, ODV, absorbed from a venlafaxine ER capsule or the time over which it is absorbed.

pubmed.ncbi.nlm.nih.gov

 

[whopper]

Venlafaxine has an extremely short half life-so even if a serum level is obtained the value is almost useless, there's no standard to utilize Venlafaxine serum levels for treatment, and the medication could possibly have no benefit even if there's a good concentration in the serum. The benefits of a medication aren't simply based on metabolism. There's other factors such as lock-and-key theory.

There's very little point in ordering a serum level. Only situations where one may be needed I could fathom is to see if the patient is non-compliant, but even then very few doctors would order a test. Then the patient's failure is on them, and try a different approach. If you want to check metabolism of the med a pharmacogenetic test is a more conventional method. Due to the complex nature of medicine perhaps there's some out-of-left-field reason that makes sense from your perspective, but if so this is likely something very out of the ordinary.

If you're in training your teacher should be educated and experienced enough to answer this. If you're not in training (unless you're a non-psych provider and maybe a different type of MD/DO just trying to do your best with what you got) and you didn't know this, wow I fear for this patient.

 

[hamstergang]

I could see someone ordering a level if there is suspicion for a rapid metabolizer and so you want to justify that it's safe (and maybe helpful) to go to a very high dose.

 

[robellis]

Venlafaxine has an extremely short half life-so even if a serum level is obtained the value is almost useless, there's no standard to utilize Venlafaxine serum levels for treatment, and the medication could possibly have no benefit even if there's a good concentration in the serum. The benefits of a medication aren't simply based on metabolism. There's other factors such as lock-and-key theory.

There's very little point in ordering a serum level. Only situations where one may be needed I could fathom is to see if the patient is non-compliant, but even then very few doctors would order a test. Then the patient's failure is on them, and try a different approach. If you want to check metabolism of the med a pharmacogenetic test is a more conventional method. Due to the complex nature of medicine perhaps there's some out-of-left-field reason that makes sense from your perspective, but if so this is likely something very out of the ordinary.

If you're in training your teacher should be educated and experienced enough to answer this. If you're not in training (unless you're a non-psych provider and maybe a different type of MD/DO just trying to do your best with what you got) and you didn't know this, wow I fear for this patient.

This is a bit harsh..

 

[Sikrouf]

Venlafaxine has an extremely short half life-so even if a serum level is obtained the value is almost useless, there's no standard to utilize Venlafaxine serum levels for treatment, and the medication could possibly have no benefit even if there's a good concentration in the serum. The benefits of a medication aren't simply based on metabolism. There's other factors such as lock-and-key theory.

There's very little point in ordering a serum level. Only situations where one may be needed I could fathom is to see if the patient is non-compliant, but even then very few doctors would order a test. Then the patient's failure is on them, and try a different approach. If you want to check metabolism of the med a pharmacogenetic test is a more conventional method. Due to the complex nature of medicine perhaps there's some out-of-left-field reason that makes sense from your perspective, but if so this is likely something very out of the ordinary.

If you're in training your teacher should be educated and experienced enough to answer this. If you're not in training (unless you're a non-psych provider and maybe a different type of MD/DO just trying to do your best with what you got) and you didn't know this, wow I fear for this patient.

I m a actually a doctor handling interns at a inpatient facility for SMI

I m only handling patients out of the ordinary as interns handle the "easy" cases most of the time

I ve already made my point clear; I m not sure that kind of comment is of any use but to each is own I guess

I said weird because I was just after a quick answer and didnt have time to write much more than that

I wont be answering anymore to attacks in this thread, "I fear for your patient because you ordered a blood level", seriously? Cant you disagree without feeling the urge to attack someone ? Are you THAT confident you're right ? Sigh

Take care