Pharmaceutical Drugs

The Pharmaceutical industry is one of the world’s largest industries, grossing well over $300 billion in the United States alone. Understanding how the drugs the pharma industry develops work and different characteristics of these compounds is important to nearly everyone as 50% of the US population takes at least one prescription medication regularly and nearly everyone takes a pharmaceutical pill at some point in their life.

This page will serve as a simple explanation of how specific pharmaceutical compounds work and what their “pharmacokinetic” characteristics are.

Pharmacokinetics TranslatedPharmacokinetics Translated

Pharmacokinetics (PK) measures the variations of drug levels in the body with relation to how much compound you take and time since taking the drug.

Bioavailability (F)Bioavailability (F)

This is the amount of a drug that actually makes it into your bloodstream as compared to the amount you put in your mouth, inhale, or inject. Since the body has dozens of defense mechanisms to keep foreign compounds out of your blood, simply getting the active compound into your bloodstream is pretty difficult. Drug compounds must pass through the hostile stomach, must avoid setting off an immune response, must avoid being metabolized by the liver and ultimately be absorbed by the small intestine in order to make it into the blood.

Protein BindingProtein Binding

Once a drug compound has successfully entered the blood stream, an important consideration is how much of the drug is freely available to enter cells versus how much is bound by plasma proteins. Proteins bind drug compounds at varying rates, decreasing the rate at which drug compounds are absorbed by cells. Without such proteins, many compounds, like adrenaline, would be absorbed too fast and would not reach all of the targets in the body. Many drugs are so completely bound by protein that their availability toward absorption by cells is nearly zero.

BarriersBarriers

Certain parts of the body have barriers to entry. Cell membranes for example have a highly hydrophobic interior which excludes polar molecules to enter. Thus most drugs must pass into cells through membrane channels and membrane transport proteins. Another important barrier is the so-called “blood brain barrier”, which protects your brain and spinal cord from toxins. This is a good thing as the brain is a sensitive place, but it can be detrimental to pharmaceutical scientists attempting to develop a compound to function in the brain.

Dose (D)Dose (D)

Quite simply it is the mass of active compound you take, typically measured in mg.

Concentration(C0) or (Css)Concentration(C0) or (Css)

It either the initial or steady state concentration of the drug in the blood plasma

CmaxCmax

This is the peak concentration of a drug after administration

CminCmin

This is the lowest concentration a drug reaches before a second administration of the drug occurs.

Half Life (T1/2)Half Life (T1/2)

Typically measured in hours, it is the time required for the concentration of the drug in your blood to be reduced by ½. Once a drug enters the blood, the body will immediately start to remove it. T1/2 gives an indication of how long the drug will be active for.

Clearance (Cl)=Clearance (Cl)=

This is a measure of the volume of plasma cleared of the drug per unit of time.

Area Under the Curve (AUC)Area Under the Curve (AUC)

This is a measurement of the total exposure someone has to the curve. It is represented by the area under the PK curve. It is the integral of the concentration over time.

Inhibitory Concentration (IC50)Inhibitory Concentration (IC50)

This is a measurement of the half maximal inhibitory concentration. In other words, it is a measure of how much drug must be taken before 50% of the particular biochemical function is inhibited. It is the typical measurement of drug potency in which lower values indicate increased potency.