I, for one, take a handful of pills per day. Along with maintenance drugs for blood pressure, cholesterol, and a baby aspirin, I also take in the area of 18 to 20 vitamins.( all doctor approved). How does each pill know where to go to do it’s thing? Once the stomach acids do their thing, is there a mad scramble going on for different organs? How do they know which path to take to aid the different things they are made for?
I always assumed they all went into the blood and were picked up by the areas they were designed to appeal to.
I’m as clueless as you though, so don’t take this as an informed answer.
Mapquest?
Well, I’m not a doctor or a pharmacologist, but as far as I know, most drugs taken orally are…
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not affected much by stomach acids, aside from getting dissolved if necessary. Food is broken down by stomach acid, but if a drug would be attacked by stomach acid or any digestive compounds in that area (and can’t be protected from such) it needs to get delivered another way than down the digestive tract.
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absorbed through the stomach lining directly into blood vessels, like most of the water in fluids we drink.
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From there, they don’t ‘know which path to take’ - blood flows everywhere, and so does ever compound in it. Many drugs will only interact with receptors that are found in very specialized tissue. Some, like acetylsalicilic acid (aspirin) will affect just about all cells in the human body.
I’m not sure about drugs for cholestorol and blood pressure control, but I’d imagine that they’re of the more specialized sort. But they still don’t ‘know’ to go anywhere… some drug receptors will find the right place and get to work. Others will take a little longer. I’d imagine that over the course of a few hours to a day, depending on a number of factors, enough will have found their way there (or gotten broken down by accident elsewhere in the body) that the concentration of the drug in your bloodstream will drop to a few percent of when it was just recently absorbed.
Does that help at all??
chrisk is correct. I wondered this about aspirin (how does it find the pain?!?!) and discovered that with pain and inflammation comes the release of certain things prostoglandins. Aspirin travels through the blood until it finds these prostoglandins and inhibit their production. With over 250 different cell types and anywhere from 30,000-100,000 different proteins in your body there’s a lot of room for good drug selectivity. Of course drugs don’t always act where they should, especially since many signalling proteins are very similar, so blocking one usually affects others which is why a lot of drugs have side effects at high enough doses.
Chrisk was almost right.
Most drugs aren’t absorbed through the stomach lining though, rather they are absorbed in the small intestine. Aspirin and alcohol are two notable exceptions, which go straight from the stomach into the blood.
There are a lot of drugs which work on certain receptor subtypes found in specific tissues and organs. For example, Beta-blockers work by blocking the effects at beta-adrenergic receptors in the heart, blood vessels and lungs. Because they affect the lungs most types of beta blockers aren’t safe for asthmatics, but some types are more specific for the blood vessel receptors, and so are safer for people who have asthma.
As others have said: they don’t know where to go. That’s why you get side-effects with a lot of drugs.
One of the more interesting and intuitive techniques used for a drug to inhibit some undesirable behavior is by clogging a particular receptor – “docking”, as they call it, in the receptor, thereby interrupting some unwanted process.
Once when I went to speak with a scientist about one of our computer applications, I noticed a beautiful multi-color diagram on the wall of a very fancy molecule. It didn’t look like the stick-and-ball models we usually see; it was more like a lumpy amorphous form. The researcher pointed to a particular little pocket in the corner of the lumpy molecule and told me that his team was interested in finding something that could fit perfectly in that pocket. This was so cool: a five-year-old child could have understood what they were trying to accomplish.
They have been using molecular modeling in computers for many years now to try and identify chemical structures (hopefully in the existing company library) that can fit in particular docking sites.
This is but one of many techniques available for inhibiting processes, but it is a common one, and you can imagine that a flood of very carefully shaped molecules in the bloodstream would only dock in the desired receptors.
Oh yes, and about the delivery of the drug: there are many paths where the drug can find its way to the target, but not all drugs are as capable of following all paths. This is why some drugs must be delivered by injection; others by topical application; still others by ingestion. Clearly, one prefers drugs that can be taken in pill form, but many cannot survive the trip.
When a new drug candidate molecules are being selected for a particular target, potential molecules are evaluated on many criteria such as toxicology and how easily it can reach the target (e.g. can it cross the blood-brain barrier?).
minor7flat5: The diagram is usually called a ‘space-filling model’, if it’s made up of spheres that represent the radii of the atoms. If each sphere was color-coded (red for oxygen, blue for nitrogen, black for carbon, white for hydrogen, and so on), that’s probably what it was. If it was a lumpy, smooth shape, then it was an electron density surface that shows what the ‘electron cloud’ around the nuclei looks like. This is more accurate than a space-filling model made of spheres if you want to know how the molecule will react with others. Electron density surfaces are often color-coded to represent various things – areas of slightly more positive and slightly more negative charge are common. Designing a molecule that will fit in the pocket is about more than finding one that’s the right shape – it also has to have negative and positive charges in the right places, so it will actually stay in the pocket once it gets there.
Another way to design a drug that will inhibit the activity of an enzyme is find out how the enzyme works and look at the transition state, an intermediate in the process of the enzyme changing one molecule to another that generally binds to the enzyme very tightly, but not permanently. If you can design a molecule that resembles the transition state in the enzyme’s usual process but that binds to it permanently, or at least much more strongly than the usual transition state, you can inhibit the enzyme. In a course on enzyme mechanisms, we looked at how this was done in the design of HIV protease inhibitors, which are molecules that resemble the transition state of the viral proteins that HIV protease cuts apart, but that bind so tightly to the HIV protease that it can’t function once the drug has bound.