Common Crazy Med Crap Index
Metabolism & Elimination | Pharmacology Index

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  1. 1. Bibliography

Why is knowing about absorption, distribution, bioavailability and other obscure crap important?

  • Absorption can be affected by food. Knowing how much of a difference it makes when you take a med after eating vs. on an empty stomach may not seem like a big deal, until you can’t eat much of anything.
    • Say if you got very sick
    • Or had gastric bypass surgery
    • Or the med makes you want to puke when you take it on an empty stomach
  • Bioavailability and distribution explain why some meds are vastly more potent than others (e.g. Paxil and Prozac), but there’s not a lot of difference in their dosages.
  • Bioavailability factors determine if a generic medication is functionally equivalent to the original brand-name drug. You can’t call bullshit on the generic’s manufacturer if you don’t understand the numbers, because the FDA claims any difference you experience is imaginary or coincidental.

Bioavailability made simple: practically all injected drugs are about, if not absolutely 100% bioavailable.
As most of the drugs we deal with here are taken orally (even if they do have an injectable version available), the simple version of bioavailability usually isn’t an option. So what do you need to know about bioavailability? Unless you’re studying to be a pharmacist or doctor, or you just like to learn everything you can about a med, you don’t need to know any of this.
Except when there’s a problem with a generic medication, and you want to figure out what the hell is wrong14. Not that you could do anything about it, or that the data on the generic medication are readily available, but it’s nice to know that the problem isn’t in your head. Rather the generic med in question doesn’t act the same way as the brand or another generic somewhere between your stomach and your brain. The most notorious example of this to date is Teva’s Budeprion XL version of Wellbutrin XL. We go into great detail about it in the section on branded vs. generic drugs, with an example of how these data are used.
The plasma half-life is the same as above and repeated here just to make it easier to perform any calculations you may want to do.


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However, the FDA requires only a single, frequently sub-therapeutic dose taken by healthy volunteers to test pharmacokinetic data, including bioavailability and bioequivalence factors. Until recently all pharmacokinetic data for a drug were based on a single study done on fewer than 20 healthy volunteers, who were mostly, if not all white males between the ages of 20 and 50 willing to take recently developed drugs because they need the money. Those guys took a single dose, which was often lower than the typical starting dosage, on an empty stomach, first thing in the morning. The only way to tell if the data is from the real world (e.g. from people with the condition the med treats who are in stage III clinical trials) is to look at the Full US Prescribing Information / PI Sheet in the pharmacokinetics section. If it doesn’t tell you how many people participated with demographic data, assume it was a handful of healthy white guys desperate for cash.
You can probably tell how those crappy studies create a big problem with pharmacokinetic data.

Fortunately more and more pioneering pharmaceutical companies (the ones that make the original, brand-name drugs) are using far more people in their studies, including those with the conditions as well as healthy volunteers to determine all PK data, they are not required to do so. By the US FDA. Other countries have different standards, and that forces big pharma to provide better PK data.
But unless a it’s a completely new drug that has been approved recently, or an existing drug that has been recently approved for a very different application, including overseas approvals, the PK data are probably from a dozen white guys who needed the money.


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Common Crazy Med Crap Index
Metabolism & Elimination | Pharmacology Index


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1.  Bibliography

Stahl’s Essential Psychopharmacology: Neuroscientific Basis and Practical Applications (Essential Psychopharmacology Series) Third edition by Stephen M. Stahl © 2008 Published by Cambridge University Press.
Primer of Drug Action 12th edition by Robert M. Julien Ph.D., Claire D. Advokat, Joseph Comaty © 2011 Published by Worth Publishers.
Genetic Basis of Drug Metabolism

11 See footnote 2 above. The good news is generic manufacturers are required to be at least 90% sure of everything being within the 80–125% range.12 If we see any evidence of a generic manufacturer ever doing more to establish the 80–125% bioequivalence standard than giving one small dose of the med to the 20 white guys who have already sold their monthly allotment of plasma, we’ll note it.

12 I know that’s not what a 90% confidence interval really means, but sometimes that’s what it seems like. Which is why we list all known generics (if any are available) that have been independently verified to meet the 80–125% standard on {{$$brandname}}’s Expanded Brand & Generic page?.


Pharmacokinetics 101 - Absorption, Distribution & Bioavailability by Jerod Poore is copyright © 2012 Jerod Poore

Last modified on Thursday, 27 March, 2014 at 18:34:53 by JerodPoorePage Author: Jerod PooreDate created: 28 April, 2012

All drug names are the trademarks of someone else. Look on the appropriate PI sheets or ask Google who the owners are. The way pharmaceutical companies buy each other and swap products like Monopoly™ real estate, the ownership of any trademarks may have changed without my noticing.





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Almost all of the material on this site is by Jerod Poore and is copyright © 2004, 2005, 2006, 2007, 2008, 2009, 2010, 2011, 2012, 2013, and 2014 Jerod Poore. Except, of course, the PI sheets - those are the property of the drug companies who developed the drugs the sheets are about - and any documents that are written by other people which may be posted to this site will remain the property of the original authors. You cannot reproduce this page or any other material on this site outside of the boundaries of fair use copying without the express permission of the copyright holder. That’s usually me, so just ask first. That means if want to print out a few pages to take to your doctor, therapist, counselor, support group, non-understanding family members or something like that - then that’s OK to just do. Go for it! Please. As long as you include this copyright notice and something along the lines of following disclaimer, I’m usually cool with it.



All rights reserved. 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. If you still have questions about a medication or condition that were not answered on any of the pages you read, please ask them on Crazy Talk: the Crazymeds Forum.
The information on Crazymeds pertains to and is intended for adults. While some information about children and adolescents is occasionally presented (e.g. US FDA approvals), pediatric-specific data such as dosages, side effects, off-label applications, etc. are rarely included in the articles on drugs or discussed on the forum. If you are looking for information regarding meds for children you’ll have to go somewhere else.
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All information on this site has been obtained through our personal experience and the experiences family, friends, what people have reported on various reputable sites all over teh intergoogles, the medications’ product information / summary of product characteristic (PI/SPC) sheets, and from sources that are referenced throughout the site. As such the information presented here is not intended as a substitute for real medical advice from your real doctor, just a compliment to it. You should never, ever, replace what a real doctor tells you with something from a website on the Internet. The farthest you should ever take it is getting a second opinion from another real doctor. Educate yourself - always read the PI/SPC sheet or patient information leaflet (PIL) that comes with your medications and never ever throw them away.
Crazymeds is not responsible for the content of sites we provide links to. We like them, or they’re paid advertisements, or they’re something else we think you should read to help you make an informed decision about a particular med. Sometimes they’re more than one of those things. But what’s on those sites is their business, not ours.
Very little information about visitors to this site is collected or saved. From time to time I look at search terms used and which pages they bring up in an effort to make the information I present more relevant. And the country of origin, just because I’m geeky like that. That’s about it. Depending on how you feel about Schrodinger, our privacy policy should either assuage or exacerbate your paranoia.
All brand names of the drugs listed in this site are the trademarks of the companies named on the PI/SPC sheet associated with the medication, sometimes on the pages about the drugs, even though those companies may have been acquired by other companies who may or may not be listed in this site by the time you read this. Or the rights to the drug were sold to another company. And any or all of the companies involved may have changed their names.
Crazymeds is optimized for the browser you’re not using on the platform you wish you had. Between you and me, it all looks a lot cleaner using Safari or Chrome, although more than half of the visitors to this site use either Safari or Internet Explorer, so I’m doing my best to make things look nice for IE as well. I’m using Firefox and running Windows 72. On a computer that sits on top of my desk. With a 23 inch monitor. Hey, at least you can make the text larger or smaller by clicking on the + or - buttons in the upper right hand corner. If you have Java enabled. Like 99% of the websites on the planet, Crazymeds is hosted on domain running an open source operating system with a variety of open source applications, including the software used to display what you’ve been reading. As such Crazymeds is not responsible for whatever weird shit your browser does or does not do when you read this site3.
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1 While there are plenty of books to help you with hypochondria, for some reason there’s not much in the way of websites. Then again, staying off of the Internet is a large part of curing/managing the disorder.

2 Remember kids, Microsloth operating systems are like TOS Star Trek movies with in that every other one sucks way, way more. With TOS Star Trek movies you don’t want to bother watching the odd-numbered ones. With Microsloth OS you don’t want to buy and install the even-numbered ones. Anyone who remembers ME and Vista knows what I mean.

3 Have I mentioned how open source operating systems for commercial applications is one of the dumbest ideas in the history of dumb ideas?
[begin rant] I rent a dedicated server for Crazymeds. It’s sitting on a rack somewhere in Southern California along with a bunch of other servers that other people have rented. The hardware is identical, but no two machines have exactly the same operating systems. I don’t even need to see what is on any of the others to know this. If somebody got their server at the exact same time, with the exact same features as I did, I’m confident that there would be noticeable differences in some aspects of the operating systems. So what does this mean? For one thing it means that no two computers in the same office of a single company have the same operating system, and the techs can spend hours figuring out what the fuck the problem could be based on that alone. It also means that application software like IP board that runs the forum here has to have so many fucking user-configurable bells and whistles that even when I read the manual I can’t find every setting, or every location that every flag needs to be set in order for a feature to run the way I want it to run. And in the real world it means you can get an MBA not only with an emphasis on resource planning, but with an emphasis on using SAP - a piece of software so complex there are now college programs on how to use it. You might think, “But don’t people learn how to use Photoshop or Adobe Illustrator in college?” Sure, in order to create stuff. And in a way you’re creating stuff with SAP. But do you get a Bachelor of Fine Arts degree with an emphasis on Photoshop?
Back in the Big Iron Age the operating systems were proprietary, and every computer that took up an entire room with a raised floor and HVAC system, and had less storage and processing power than an iPhone, had the same operating system as every other one, give or take a release level. But when a company bought application software like SAP, they also got the source code, which was usually documented and written in a way to make it easy to modify the hell out of it. Why? Because accounting principles may be the same the world over, and tax laws the same across each country and state, but no two companies have the same format for their reports, invoices, purchase orders and so forth. Standards existed and were universally ignored. If something went wrong it went wrong the same way for everyone, and was easy to track down. People didn’t need to take a college course to learn how to use a piece of software.
I’m not against the open source concept entirely. Back then all the programmers read the same magazines, so we all had the same homebrew utilities. We even had a forerunner of QR Code to scan the longer source code. Software vendors and computer manufacturers sponsored conventions so we could, among other things, swap recipes for such add-ons and utilities. While those things would make our lives easier, they had nothing to do with critical functions of the operating system. Unless badly implemented they would rarely cause key application software to crash and burn. Whereas today, with open source everything, who the hell knows what could be responsible some part of a system failing. [/end rant]

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