Bioavailability refers to how chemicals are absorbed by humans and animals, with applications in pharmacology and environmental science. It can determine drug dosages and evaluate medication delivery. Factors such as metabolism and storage can affect bioavailability. Environmental bioavailability studies can assess the presence of toxic substances in animals and plants, with potential impacts on human health. Examples include mercury levels in fish and DDT use as a pesticide. Bioavailability studies are important for responsible ecological choices.
Bioavailability is a term used by several branches of scientific study to describe how chemicals are absorbed by humans and other animals. Bioavailability was once strictly ascribed to pharmacology, but now has broad applications in environmental sciences as well. Examining the bioavailability of a substance in pharmacological studies helps determine dosages for particular drugs. A measurement of the bioavailability of a drug, as it reaches the circulation in the body, describes things like absorbency and half-life. It can also evaluate the delivery of medications.
Intravenous drug administrations are thought to have 100% bioavailability because they do not pass through the stomach. They are immediately in the circulatory system. However, other concomitantly administered drugs may reduce the effects of an intravenous administration and influence its bioavailability.
Pharmacology also distinguishes between absolute bioavailability and relative bioavailability. Absolute bioavailability is the measurement of a drug once it passes through the intestines and is released into the circulatory system. Relative bioavailability is a term used to compare different formulations of the same drug, such as brand name versus generic.
Some studies have found that some generic preparations are not equivalent in bioavailability to the brand-name versions of the drugs. An example of this is the drug Synthroid, which is usually marketed in generic form as thyroxidine. Many patients using thyroid replacement therapy find that thyroxidine is not as effective as Synthroid. Technically, the two drugs should be equivalent, but differences in the bioavailability of the two forms have been noted in studies. This, however, doesn’t change most of the insurance coverage regarding this drug. Typically, you will still have to pay extra to purchase Synthroid.
Other factors may affect bioavailability when drugs are taken orally. Slow or fast metabolism can change the absorption rate of drugs. Factors outside the body, such as improper storage of medications, can lead to lower-than-expected bioavailability results.
Bioavailability, when used in environmental science, evaluates the rate and amount of toxic substances that can occur in the body. An example of this is the recent concern over mercury levels in fish. Some fish contain high levels of mercury, a poison, which can lead to serious illness if ingested in large quantities. People who eat a lot of fish can get mercury poisoning. Recent US FDA recommendations suggest consuming mercury-rich fish no more than once a week.
Another bioavailability study that has raised concerns about our relationship to the environment is the discovery of small amounts of jet fuel secreted in human breast milk. So far no one has suggested that mothers stop breastfeeding their babies, but the study raises concerns about many things we take for granted, like flying planes or rockets, which can actually increase the risk of health problems for babies and adults.
Bioavailability studies can also compare animal or plant populations with the presence of toxic chemicals in an environment. Of concern is the degree to which these chemicals are present in animals when they reach the circulatory system and what possible effects they may have on animal populations.
For example, animal populations subsequently consumed by humans consumed plant populations coated with DDT. Some effects in humans have been an increase in certain types of cancer and autoimmune diseases. Humans could also consume DDT through plant material, creating similar problems. These studies led to a ban on DDT, which was once commonly used as a pesticide.
The bioavailability of toxins in our environment, if studied, can have a significant impact on our quality of life and our choices. These studies are invaluable, as they can help us approach our ecology with a sense of responsibility and with an eye to the future.
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