Determining dosage amount is determined while testing the toxicity of a drug. That means, at what point is the drug toxic or harmful to the human body. The next function is determining how much of the drug actually gets absorbed by the human body. Then of course is how it will be absorbed. The ultimate goal is to get to 100% of the drug being absorbed, but the more complex the drug, the less of a tendency for 100% absorption. That is one reason you might see certain drugs with 5 different dosage strengths. There are additional reasons for the 5 dosage strengths but absorption is one of them. Let’s discuss the different ways for prescription pills to be absorbed.
The majority of prescription drugs are taken orally. When you swallow a pill, it goes down your esophagus and into your stomach either with food or without. So if you take it with food, your pill starts to break down in your stomach along with the food. Now your stomach doesn’t have a stirring mechanism to get all the nutrients out. Instead the acidity breaks down what it can and creates for lack of a better word a clump or ball (bile) of processed nutrients to pass along the rest of your digestive system.
At this point, your body has absorbed about 50-60% of the nutrients. The rest are clumped and passed along until it gets into your large intestine where further absorption occurs. So picture a ball of dough sliding down tubes inside of you. As it rolls, it breaks down a little bit more and additional nutrients get absorbed. This ball never completely breaks down so what is in the center of the ball never gets absorbed. Chances are a small amount of the tablet is lodged in the center and never gets absorbed.
So your next thought is to not eat so the whole tablet breaks down. A lot of prescription drugs have this option but a few prescription drugs if consumed without food will actually damage your stomach lining (ulcers). Keep in mind that a pill has fillers and complex sugars used to bind to the active ingredient. The same ball action occurs with what is left but there is a higher percentage of absorption.
There are drugs that are enteric coated. This just means that there is a coating on the outside of the drug to prevent the stomach acid from breaking down the pill. These drugs were designed to be absorbed in your small or large intestines. Again, you won’t get 100% absorption especially since you have reduced the amount of time the drug can be absorbed. When these drugs reach the large intestine, they have to break down and get absorbed quickly. The enteric coated pills still face the problem of being piled together with other waste products and compacted in the large intestine. The easiest solution is to “overdose”, by which I mean give you more drug than needed without harming your body, to get the desired amount of drug.
Inhaled drugs are just the same but have a shorter distance for absorption. By breathing in medication, absorption starts in the esophagus and finishes in your lungs. Your lungs will absorb a large percentage of the drug but a portion stays in the lungs. Think of it as similar to smoking. Your lungs absorb the smoke with the nicotine but some tar residue stays behind. For inhalers, the only difference is that the excess powder will get dislodged over time. As it gets dislodged, mucous forms and eventually you remove it from your system. The great thing about inhalable medication is that it is delivered right into the blood stream after your lungs filter it.
Did you know about the absorption rate of medication?