Introduction to Pharmacokinetics

The extent to which a drug binds to proteins in the plasma, mainly albumin and alpha 1 acid glycoprotein.

Drugs that are attached to plasma proteins. They cannot distribute, metabolize, eliminate, or interact with receptors to produce effects.

Drugs that are not bound to proteins. They are free to distribute, metabolize, eliminate, and interact with receptors.

PPB affects how drugs are distributed, metabolized, and eliminated in the body. It also affects how the drug interacts with its target.

Acidic drugs tend to bind more strongly to albumin, while basic drugs bind more strongly to alpha 1 acid glycoprotein.

Bound drugs cannot interact with the receptor because they are trapped with the protein. They cannot reach the target site to initiate a response.

Sites where drugs are temporarily stored in the body, not for permanent storage. These are typically not the target site.

Free drugs can pass through biological membranes and reach their target. They are small enough to pass through the membrane.

Higher PPB leads to lower free drug concentration, potentially decreasing drug efficacy.

Conditions altering PPB, like renal or hepatic impairment, require dosage adjustments.

Drugs with high PPB can increase toxicity risk in patients with altered PPB.

Low albumin levels (hypoalbuminemia) can increase free drug concentration, potentially leading to toxicity.

Certain medications can compete for binding sites on plasma proteins, affecting drug efficacy.

Inflammation can alter PPB, potentially affecting drug efficacy.

A type of capillary found in most parts of the body. It has loose junctions between endothelial cells, allowing for easy passage of substances.

A specialized barrier formed by tight junctions between endothelial cells in brain capillaries, preventing the passage of most substances from the blood into the brain.

Only lipid-soluble (fat-loving) and unionized (not charged) molecules can pass through the Blood Brain Barrier.

A barrier between the mother and fetus, composed of chorionic villi, trophoblastic cells, and a basement membrane, protecting the fetus from harmful substances.

The Placental Barrier is less effective than the Blood Brain Barrier at preventing harmful substances from reaching the fetus. Some substances can cross and harm the developing baby.

Lipid-soluble, unionized drugs can easily pass through the Placental Barrier. Highly polar, large, or water-soluble drugs (like heparin and penicillin) cannot.

A hypothetical volume of body fluid into which a drug is uniformly distributed at a concentration equal to that in plasma.

Drugs with a low Vd (low volume of distribution) bind strongly to plasma proteins, meaning they are less able to distribute throughout the body's fluids.

The process by which the body breaks down and eliminates drugs. It involves two phases: Phase I (modification) and Phase II (conjugation).

The first stage of drug metabolism. It involves modifying the drug's structure by adding or removing functional groups. This often makes the drug more water-soluble, facilitating excretion.

The second stage of drug metabolism. It involves attaching a larger, water-soluble molecule (conjugate) to the drug, making it even more excretable.

A family of enzymes primarily responsible for the metabolism of drugs in the liver. They are also found in other organs like the lungs, brain, and intestines.

The most abundant CYP450 isoenzyme, responsible for metabolizing a wide variety of drugs.

A process where certain drugs or chemicals increase the activity of CYP450 enzymes. This can speed up drug metabolism and reduce their effectiveness.

A process where certain drugs or chemicals decrease the activity of CYP450 enzymes. This can slow down drug metabolism and increase drug levels in the body.

When two or more drugs interact with each other, affecting their metabolism and effectiveness. This can occur due to enzyme induction or inhibition.

Factors like molecular size & weight, lipid-solubility, degree of ionization, plasma protein & extra vascular protein binding, and disease states influence Vd.

A drug with a high Vd distributes extensively throughout the body, binding to tissues like muscles, fat, and organs.

A drug with a low Vd stays primarily in the blood, meaning it doesn't enter tissue compartments as much.

Overdose of a drug with high Vd is difficult to treat because it's spread throughout the body, making removal challenging.

A medical procedure to filter waste, fluids, and electrolytes from the blood for patients with non-functional kidneys.

An initial larger dose of a drug given to quickly achieve therapeutic levels in the blood, particularly for drugs with high Vd.

When a high Vd drug reaches its maximum binding capacity in tissues, subsequent doses primarily stay in the bloodstream, leading to therapeutic effects.

The rate of drug elimination is directly proportional to the drug's plasma concentration. This means that as the concentration of the drug in the blood increases, the rate of elimination also increases.

The rate of drug elimination is constant and independent of the drug's plasma concentration. This means that the body eliminates a fixed amount of drug per unit of time, regardless of the concentration.

The point where the rate of drug administration equals the rate of drug elimination. This means that the amount of drug in the body remains relatively constant over time.

The time it takes for the plasma concentration of a drug to decrease by half. This is a measure of how quickly a drug is eliminated from the body.

The ratio of the toxic dose to the therapeutic dose of a drug. A drug with a low therapeutic index has a narrow margin of safety.

It ensures a constant drug amount in the body, avoiding both acute toxicity and decline of drug effect. This is important for drugs with low therapeutic indices where precise dosing is crucial for efficacy and safety .

It takes approximately 4-5 half-lives to reach steady state concentration. This is because with each half-life, the drug concentration gets closer to the steady state level.

Drugs with a low therapeutic index, like digoxin and theophylline, require careful monitoring of their steady state concentration to avoid toxicity and ensure efficacy.