Drug metabolism, which is the biochemical translation of pharmaceuticals by internal human organ systems, can be hindered or accelerated by multiple factors. Modified metabolism of drugs can lead to toxication, which is an exaggerated activation of the chemical compound, or detoxication, which is an over deactivation. These processes can be caused by factors like absorption and bioavailability, pathogenesis, and the inhibition of certain enzymatic pathways. The majority of drug metabolism takes place in the liver — other less active sites exist in the gastrointestinal (GI) tract, lungs, and kidneys. For this reason, studies done on factors known to interfere with drug metabolism focus on these systems, in particular.
The absorption and subsequent bioavailability of active drug compounds is often times the first interference considered when studying drug metabolism. Absorption and bioavailability dictate how quickly and in what level a drug reaches its target organ. In this regard, these processes greatly affect the rate at which drug metabolism takes place. Improper absorption can be caused by diseases or malfunction of the GI tract; it can also vary due to a drug’s pharmacological method of administration. Methods of administration that require the drug to pass through the stomach, for example, can be affected by the specific rate of absorption by the patient. Patients who have a stomach acidity lower than a normal pH may have trouble absorbing many drug compounds.
Food and other drugs can sometimes interfere with absorption rates as well. For example, high-fiber foods have a tendency to bind with many compounds, preventing them from being absorbed at normal rates. Over-the-counter laxatives and diuretics may affect how much active drug remains in the system, determining its efficacy after metabolizing. Enzymatic pathways, crucial for the metabolism of drugs, can be hindered by certain foods and other medications that the patient is prescribed. In these cases, chemicals inherent in food, like the grapefruit, for example, use the same enzyme for metabolism that many drugs do. If both the food and the medication are taken at the same time, metabolism of the drug may be significantly inhibited.
Within the liver, an organelle known as the rough endoplasmic reticulum is indicated in the initial metabolism of drugs. As the drug passes into this system, the beginning stages of drug metabolism take place. This phase is called the drug’s first pass, referring to its first pass through the organ of major metabolism, the liver. Any mechanical malfunction or disease present within the liver can affect drug metabolism upon the first pass.