Highlighting pharmacokinetics, pharmacodynamics and mechanism of action

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US brand name: Abilify
Generic name: aripiprazole

Pharmacology

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

Half-lives: 75 hours for Abilfy, 94 hours for its active metabolite. Clearance: 20 days!

Steady State

Steady state reached in about 14 days

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 aripiprazole Works

the current best guess at any rate

According to Otsuka:

12.1 Mechanism of Action
The mechanism of action of aripiprazole, as with other drugs having efficacy in schizophrenia, bipolar disorder, major depressive disorder, irritability associated with autistic disorder, and agitation associated with schizophrenia or bipolar disorder, is unknown. However, it has been proposed that the efficacy of aripiprazole is mediated through a combination of partial agonist activity at D2 and 5-HT1A receptors and antagonist activity at 5-HT2A receptors. Actions at receptors other than D2, 5-HT1A, and 5-HT2A may explain some of the other clinical effects of aripiprazole (eg, the orthostatic hypotension observed with aripiprazole may be explained by its antagonist activity at adrenergic alpha1 receptors).

12.2 Pharmacodynamics
Aripiprazole exhibits high affinity for dopamine D2 and D3, serotonin 5-HT1A and 5-HT2A receptors (Ki values of 0.34 nM, 0.8 nM, 1.7 nM, and 3.4 nM, respectively), moderate affinity for dopamine D4, serotonin 5-HT2C and 5-HT7, alpha1-adrenergic and histamine H1 receptors (Ki values of 44 nM, 15 nM, 39 nM, 57 nM, and 61 nM, respectively), and moderate affinity for the serotonin reuptake site (Ki=98 nM). Aripiprazole has no appreciable affinity for cholinergic muscarinic receptors (IC50>1000 nM). Aripiprazole functions as a partial agonist at the dopamine D2 and the serotonin 5-HT1A receptors, and as an antagonist at serotonin 5-HT2A receptor. Abilify PI sheet

Based upon my research Aripiprazole is a moderate antagonist at the dopamine D3 receptor and a potent antagonist at the serotonin 5-HT2A receptors. Like quetiapine, ziprasidone, and clozapine, aripiprazole is a partial agonist at serotonin 5-HT1A receptors, but what makes it special (in the US, for now) is also being a partial agonist at the dopamine D2 receptors. Blocking 5-HT2A, and having a positive effect on 5-HT1A and D2 are responsible for fewer movement disorder and prolactin problems, and all those agitating/antsy/activating side effects. Excluding akathisia.

“Positive” isn’t quite the right word. As a partial agonist, aripiprazole fine tunes 5-HT1A and D2, which are happy brain juice receptors.

One thing that does makes aripiprazole unique, it’s the first crazy med I’ve written about where I think it actually does fewer things than are published in the PI sheet! Although I may have to re-evaluate the effect on H1, and make it wildly variable from person to person.

Active Ingredient

aripiprazole

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

Tablets & ODT - 3 years. Oral solution - 3 years (6 months after opening). IM Injection- 18 months.



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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 16:32:50 by JerodPoorePage Author Date created Tuesday, 29 November 2011 at 11:57:45
“Abilify (aripiprazole) Pharmacology” by Jerod Poore is copyright © 2011 Jerod Poore Published online 2011/11/29

Abilify, and all other drug names on this page and used throughout the site, are the trademarks of someone else. Abilify’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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