I understand that certain food’s acidity can affect absorption and other substances in food can interfere with liver enzymes… are these the two most common factors?
In: Biology
It’s different from one to the other, but a lot of it is because of binding. Some meds “stick” to calcium, so drinking milk makes less of the med free for your body to use. Sometimes it’s something in food that binds to the same protein that metabolizes the drug, so more of the drug stays in your system, making it more potent and potentially toxic.
Some drugs can be more or less fat soluble, or water soluble. Therefore, if you consume a high fat meal, more of the drug will be absorbed because it will dissolve in the fat. Same goes for a water soluble drug. Clearly, if the situations were reversed, the opposite will occur.
Another way food can affect the absorption is through affecting gastric emptying. For example, a high fat and/or protein meal leads to the secretion of a hormone known as cholecystokinin (CCK). CCK inhibits gastric emptying, meaning the drug remains in the stomach for an extended period of time.
So there are several factors
* Nutritional content of food: fatty meals decrease rate of your stomach emptying and prolong how long food may be in stomach (if the drug is absorbed in the small intestines this can decrease peak blood concentration)
* Some drugs are better absorbed at different acid levels: acidic drugs are better absorbed in the stomach and basic drugs are better absorbed in the small intestines (pH of food can alter both these environments to a small degree)
* Charged molecules can bind to drugs (calcium, magnesium, bicarbonate): many of these are found in antacids. They can decrease the overall amount of drug that can be absorbed as well as the surrounding ideal pH.
* Some foods/herbal supplements can affect liver enzymes: Generally, these don’t decrease the amount of drug absorbed but can either increase or decrease the level available in the blood. They do this by either increasing production of the metabolizing enzyme or blocking it, respectively
* Some drugs don’t like water: Some drugs prefer fat over water so route of administration can play a factor (ex. fat in a meal aids absorption of fat soluble vitamins). This is how birth control arm implants/depot shots work. This is because the birth control likes fat and tries to avoid water. Thus, the birth control only slowly leaks out of the implant and into the blood (mostly water).
* Some drugs bind blood proteins: increase or decrease of blood proteins may subsequently change how much free drug is in your blood. This may affect absorption. Some drugs compete for the same proteins.
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