Highlighting pharmacokinetics, pharmacodynamics and mechanism of action

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US brand name: Seroquel
Generic name: quetiapine

Pharmacology

Seroquel’s Half-Life & How Long Until It Clears Your System

Half-life: 12 hours. Plasma Clearance: 3 days.

Steady State

Half-life is the average time it takes for you to process half of the drug’s active ingredient. If a drug has a half-life of around 24 hours and you take a dose of 100mg, you’ll have roughly the equivalent a 50mg dose after one day, a 25mg dose after two days, and so on. The rule of thumb is: multiply the half-life by five and you get how long it is for the dose you took to be cleared from your bloodstream1.

Steady state is the flipside of half-life. This is when you can expect to get over side effects caused by fluctuating amounts of a medication in your bloodstream. Often, but not always the same amount of time as the plasma clearance above.



How quetiapine Works

the current best guess at any rate
Seroquel is a broad-spectrum atypical/second-generation antipsychotic, and is tied with Zyprexa for third place in how many, and which type, of neurotransmitter receptors it affects. Most of its activity involves reducing the activity 5HT-serotonin and alpha-1a & alpha-2c norepinephrine receptors. Like practically every AP on the planet, Seroquel is a D2 antagonist. Being a potent antagonist at 5-HT2A, 5-HT2C, and 5-HT7, a partial agonist at serotonin 5-HT1A, and a little norepinephrine reuptake inhibition accounts for its antidepressant effect. Because of that last one, and the nature of anxiety spectrum disorders, Seroquel can make you more or less anxious when you start taking it, then do the exact opposite at a higher dosage.

In a way Seroquel is a kind of off-beat third generation antipsychotic (TGA). By definition TGAs (e.g. Abilify) are both dopamine receptor antagonists and partial agonists. Seroquel is a partial serotonin agonist at 5HT2. Which is mildly ironic, as the name Seroquel probably derives from Serotonin Quelling.

Active Ingredient

quetiapine fumarate

The active ingredient is usually the same as the generic name, but more often than not it’s a chemical salt of the substance identified as the generic. E.g. Fluoxetine is the generic for Prozac, but the active ingredient is fluoxetine hydrochloride (or HCl). It usually doesn’t make much of a difference outside of the more esoteric aspects of a drug’s pharmacology, but not always.



Shelf Life

3 years



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1 After five times the half-life you'll have reached what's called "Plasma clearance," or "not enough left in your bloodstream to latch onto your brain and do anything." It's based on Julien's calculations from A Primer of Drug Action, and half-life multiplied by five is the generally accepted estimate of how long it takes a single dose of any given drug to be eliminated from the blood stream/plasma of someone with a normal metabolism. That's also the rough estimate for steady state if they can't get, or won't provide a number for that.
The next level is "Complete clearance", and is a complex equation based on a lot of factors which may or may not: be published in the PI sheet, include personal data like your weight, or even completely figured out by corporate and independent researchers. It usually winds up being within (as in usually, but not always, after) 2-5 days of plasma clearance no matter what, but sometimes can take weeks. Sometimes a drug will clear from your brain and other organs before it clears from your blood.
That's how it works for crazy meds. I have no idea what the average complete clearance is for other types of medications. For all I know there are drugs that utterly vanish from your system in under five passes, and others that won't let go of your squishy bits for years after you stop taking them.


Last modified on Wed, 04 May, 2016 at 17:54:17 by JerodPoorePage Author Date created Tuesday, 25 January 2011 at 17:03:23
“Seroquel (quetiapine) Pharmacology” by Jerod Poore is copyright © 2011 Jerod Poore Published online 2011/01/26

Seroquel, and all other drug names on this page and used throughout the site, are the trademarks of someone else. Seroquel’s PI Sheet will probably have the name of the manufacturer and trademark owner (they’re not always the same company) at or near the very bottom. Or ask Google who the owner is. The way pharmaceutical companies buy each other and swap products like Monopoly™ real estate, the ownership of the trademark may have changed without my noticing. It may of changed hands by the time you finished reading this article.



Page design and explanatory material by Jerod Poore, copyright © 2003 - 2016. All rights reserved. See the full copyright notice for full copyright details.
Don’t automatically believe everything you read on teh Intergoogles. No warranty is expressed or implied in this information. Consult one or more doctors and/or pharmacists before taking, or changing how you take any neurological and/or psychiatric medication. Your mileage may vary. What happened to us won’t necessarily happen to you. For more details see the Crazymeds big-ass disclaimer.

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