Bioavailability refers to the proportion of an unaltered drug that, after administration, enters the systemic circulation and can be distributed to the desired action site. Factors such as gastrointestinal (GI) absorption and liver biotransformation influence the bioavailability of a drug when it is administered orally. When a drug is administered intravenously, it enters the systemic circulation directly; by definition, its bioavailability is assumed to be 100%. The bioavailability of an...

Pharmaceutical substances known as xenobiotics are predominantly lipophilic and nonionized. This enables them to permeate lipid bilayers, such as cell membranes, and interact with intracellular target receptors. Lipophilic drugs have an advantage in crossing biological barriers and reaching their intended sites of action. However, lipophilic drugs often have a restricted capacity for renal expulsion or elimination from the body. When these drugs enter the kidneys and undergo glomerular...

The process of drug absorption signifies the transition of a drug from its site of administration into the plasma. This process is influenced by various factors, including the route of administration, the anatomy of the absorption site, the mechanism of absorption, gut motility, and the drug's physicochemical properties.
When drugs are injected intravenously, they directly enter the systemic circulation. Alternatively, orally administered drugs navigate through the gastrointestinal (GI)...

Pharmacokinetics is a scientific discipline that focuses on the journey of a drug within the body, encompassing four key stages: absorption, distribution, metabolism, and elimination. The first stage, absorption, involves the drug's transfer into the bloodstream. Several factors dictate the extent and speed of this process. For example, the liver often metabolizes oral drugs before they reach systemic circulation, leading to only partial absorption. In contrast, intravenous (IV)...

The biliary system of the liver, crucial for bile secretion and drug excretion, comprises intrahepatic bile ducts that merge to form the common hepatic duct. This duct, carrying hepatic bile, combines with the cystic duct, draining the gallbladder and forming the common bile duct, which empties into the duodenum. Bile, produced by hepatic cells lining the bile canaliculi, is composed primarily of water, bile salts, pigments, electrolytes, and lesser amounts of cholesterol and fatty acids. Bile...

A drug dosage regimen describes the specific instructions and schedule for administering a drug to a patient. It considers factors such as drug dosage, frequency, route of administration, and duration of treatment. Designing an appropriate dosage regimen for a patient aims to achieve a target drug concentration at the site of action.
Typically, the starting dose and dosing interval are guided by the manufacturer's recommendations based on clinical trials conducted during and after drug...