introduction to pharmacokinetics 1
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what does there need to be for a drug to exert an effective pharmacological effect?
adequate drug concentration at the target tissue
drug disposition
process by which a pharmaceutical compound (drug) is absorbed, distributed, metabolized, and excreted within an organism, typically a human or an animal
pharmacokinetics
what the body does to the drug
pharmacodynamics
what the drug does to the body
by what model can drug disposition be described
the ADME model
what does ADME stand for
Absorption Distribution Metabolism Elimination
how do you define the boundary of what is inside or outside of the body?
The epithelial cell layer defines the boundary of the body E.g. Digestive and respiratory systems classed as outside the body A substance is considered Inside the body when the substance has crossed the epithelial barrier into the bloodstream
How many different routes of drug administration can youth think of?(name at least 5)
intravitreal intranasal intramuscular transdermal subcutaneous transmucosal intrathecal epidural rectal viginal and many more…..
how do the intestinal walls and the liver serve as barriers?
the intestinal walls and the liver function as the protective barrier to prevent the entry of xenobiotics into the body
xenobiotics
foreign substances or chemical compounds that are not naturally produced or expected to be present in an organism’s body
formula for bioavailability
Bioavailability (F)= fraction absorbed (fg) * fraction escaping first-pass metabolism (fH)
describe the “first-pass effect”
The extent at which a drug is removed by the liver during the first passage into the portal vein through the liver (fraction of dose escaping first-pass effect (fH)) read the following if you want to understand more(it is from chatgpt) refers to the phenomenon that occurs when a drug is administered orally (by mouth) and is absorbed from the gastrointestinal tract, it enters the hepatic portal circulation (the network of blood vessels that carries blood from the digestive organs to the liver) before entering the systemic circulation (the bloodstream that circulates throughout the body). During this process, the drug is exposed to the liver’s metabolic enzymes before it reaches the systemic circulation. As a result, some drugs are extensively metabolized or transformed by the liver before they can exert their therapeutic effects in other parts of the body.
which organ is the first pass effect primarily linked to
the liver
what is the bioavailability of an intravenous dose
1 or 100%
to measure the bioavailability of a plasma drug on a concentration-time graph, what formula do we use
AUCoral/ AUCintravenous
what is bioavailability
The fraction of the drug that reaches systemic circulation as an intact drug
absorption of drugs in terms of bioavailability
Extent intact drug is absorbed from the gut lumen into the portal vein (fraction dose absorbed from gut (fg))
cell membranes
the barriers between compartments in the body
what does cholesterol affect in cell membranes?
the fluidity and stability of the membrane
how do lipophilic molecules cross the cell membrane
they permeate the cell membrane, i.e, they diffuse straight through the lipid bilayer
the permeability of lipid molecules through the cell membrane is dependent on?
the concentration gradient of the molecule partition coefficient
solubility in lipids is measured by?
the partition coefficient(Log P)
in what phase do lipophilic drugs partition in what phase do hydrophilic drugs partition
the hydrophobic phase aqueous phase
formula for the partition coefficient
log drug(in the hydrophobic phase)/ log drug (in the aqueous phase)