How long does Seroquel XR stay on your system?

[John101]

How long does Seroquel XR stay on your system?

 

[Mysterie]

from some googling.

it appears the half life for XR is 7-12 hours whereas IR is 6

so to my understanding XR would stay in your system up to 24 hours

 

[John101]

7-12? Can you be more precise? Can you paste here the link where you got that info? Thanks

 

[Mysterie]

section from this article (https://www.drugs.com/pro/seroquel-xr.html)

Pharmacokinetics
Adults

Following multiple dosing of quetiapine up to a total daily dose of 800 mg, administered in divided doses, the plasma concentration of quetiapine and norquetiapine, the major active metabolite of quetiapine, were proportional to the total daily dose. Accumulation is predictable upon multiple dosing. Steady-state mean Cmax and AUC of norquetiapine are about 21-27% and 46-56%, respectively of that observed for quetiapine. Elimination of quetiapine is mainly via hepatic metabolism. The mean-terminal half-life is approximately 7 hours for quetiapine and approximately 12 hours for norquetiapine within the clinical dose range. Steady-state concentrations are expected to be achieved within two days of dosing. Seroquel XR is unlikely to interfere with the metabolism of drugs metabolized by cytochrome P450 enzymes.

Children and Adolescents

At steady state the pharmacokinetics of the parent compound, in children and adolescents (10-17 years of age), were similar to adults. However, when adjusted for dose and weight, AUC and Cmax of the parent compound were 41% and 39% lower, respectively, in children and adolescents than in adults. For the active metabolite, norquetiapine, AUC and Cmax were 45% and 31% higher, respectively, in children and adolescents than in adults. When adjusted for dose and weight, the pharmacokinetics of the metabolite, norquetiapine, was similar between children and adolescents and adults [see Use in Specific Populations (8.4)].

Absorption

Quetiapine fumarate reaches peak plasma concentrations approximately 6 hours following administration. Seroquel XR dosed once daily at steady state has comparable bioavailability to an equivalent total daily dose of SEROQUEL administered in divided doses, twice daily. A high-fat meal (approximately 800 to 1000 calories) was found to produce statistically significant increases in the Seroquel XR Cmax and AUC of 44% to 52% and 20% to 22%, respectively, for the 50 mg and 300 mg tablets. In comparison, a light meal (approximately 300 calories) had no significant effect on the Cmax or AUC of quetiapine. It is recommended that Seroquel XR be taken without food or with a light meal [see Dosage and Administration (2.1)].

Distribution

Quetiapine is widely distributed throughout the body with an apparent volume of distribution of 10±4 L/kg. It is 83% bound to plasma proteins at therapeutic concentrations. In vitro, quetiapine did not affect the binding of warfarin or diazepam to human serum albumin. In turn, neither warfarin nor diazepam altered the binding of quetiapine.

Metabolism and Elimination

Following a single oral dose of 14C-quetiapine, less than 1% of the administered dose was excreted as unchanged drug, indicating that quetiapine is highly metabolized. Approximately 73% and 20% of the dose was recovered in the urine and feces, respectively. The average dose fraction of free quetiapine and its major active metabolite is <5% excreted in the urine.

Quetiapine is extensively metabolized by the liver. The major metabolic pathways are sulfoxidation to the sulfoxide metabolite and oxidation to the parent acid metabolite; both metabolites are pharmacologically inactive. In vitro studies using human liver microsomes revealed that the cytochrome P450 3A4 isoenzyme is involved in the metabolism of quetiapine to its major, but inactive, sulfoxide metabolite and in the metabolism of its active metabolite norquetiapine.

then this quote from aurochs which is a more simple explanation of that quote^, found in this thread (http://www.crazyboards.org/forums/i...t-find-the-half-life-of-seroquel-xr-anywhere/)

To be more direct: 800 mg of Seroquel XR lasts about 24 hours, which is twice as long as 400 mg of Seroquel IR. Since the IR would need to be taken twice a day, the actual exposure is the same in either case.

then used this to help corroborate, a post from another poster in that thread from crazyboards

according to epocrates (pill app for iphone that i LOVE) says the half life is 7-12 hours where as the IR is 6 hours.

 

[John101]

So 800 mg XR is the dose that lasts all day. Isn't that to much of a dose? When I say I used to take 200mg per day people already say "WOW".

 

[Mysterie]

first i should preface i'm not a doctor and am not trying to play one on the internet. in order to get the best medical advice you should consult your doctor about the medication

but i'll try interpret the information i've read.

it seems that if you would normally take 100mg of seroquel IR twice a day (in order to maintain the exposure of seroquel in your bloodstream all day)

200mg of seroquel XR, taken once a day, would have the same exposure due to it staying in your body by almost twice the length of time that IR does.

what dosage do you currently take at the moment of seroquel IR? you take it once a day i'm guessing?

 

[Erikmen]

^ Precisely

I had given an example of how it works on his previous thread.