D&B Chapter 4 Pharmacology

Pharmacokinetics

The study of how drugs are handled by the body—how they are absorbed into the bloodstream, distributed throughout the body, transformed into different chemicals, and excreted.

Absorption

The process by which drugs pass from the external world into the bloodstream.

Factors affecting absorption

Dosage, route of administration, solubility, and pH.

Dosage

Depends on the nature of the drug, the person's body weight, and their prior experience with the drug.

What are the routes of administration?

Includes oral, rectal, vaginal, sublingual, intranasal, transdermal, inhalation, and intravenous injection.

What can affect drug distribution?

Drug's solubility, size, whether it is bound to plasma proteins.

Drug depot

An area of the body that can accumulate and store a drug, but where no significant biological effect of the drug occurs.

Blood-brain barrier

A system of capillaries that prohibits most water-soluble substances from entering the brain.

Placenta

Not an effective barrier to drug distribution; almost all drugs in a mother's blood supply will enter the fetus's circulation.

Metabolism

The process by which the body accepts a drug, alters it chemically, and prepares it for excretion.

Liver

The most important organ for metabolism.

Cytochrome P450 enzymes

Many drugs are metabolized by these enzymes in the liver.

Factors influencing metabolism

Genetics, size, age, sex, other foods or drugs, and environment.

First-pass effect

When the liver metabolizes an orally administered drug before it reaches the systemic circulation, thus reducing its bioavailability.

First-order kinetics

The rate of the drug's metabolism is proportional to the concentration of the drug.

Zero order kinetics

The rate of the drug's metabolism is constant over time and independent of the concentration of the drug.

Kidney

The most important organ for elimination.

Drug interactions

When two drugs are both metabolized by CYP450 enzymes, there is a potential for interactions.

What is pharmacodynamics?

The study of the mechanisms by which a drug exerts its effects.

What is a ligand?

Any molecule that binds to a receptor.

What does it mean if a receptor exists for a substance?

It means there is an endogenous ligand that will bind to that receptor.

What is an agonist?

A drug that mimics the effects of a neurotransmitter, which can be excitatory or inhibitory.

What is a full agonist?

An agonist that binds directly to the receptor and produces the maximum effect.

What is a partial agonist?

An agonist that binds and partially activates a receptor.

What is an antagonist?

A substance that prevents a neurotransmitter from having its effect.

What is an inverse agonist?

A substance that binds to the main receptor site and stops all receptor activity.

What are allosteric modulators?

Substances that bind to an alternate site on the receptor and influence the effect of agonists.

What are direct ionotropic receptors?

Receptors that are ion channels, opening quickly when a neurotransmitter binds.

What are metabotropic receptors?

Receptors that require a series of events to open an ion channel, taking more time to produce an effect.

What is a placebo?

A pharmacologically inert substance that can elicit a significant therapeutic response.

What influences a person's drug experience?

The setting, which includes the physical, social, and cultural environment in which a drug is taken.

What are side effects?

Pharmacological actions that occur in addition to the main action of a drug.

What does the dose-response curve measure?

The magnitude of a drug's effect as a function of the dose.

What is the therapeutic index (TI)?

A measure of the safety of a drug, expressed as a ratio of the lethal dose to the effective dose.

What are pharmacokinetic drug interactions?

Interactions that occur when one drug alters the absorption, distribution, metabolism, or excretion of another.

What are pharmacodynamic drug interactions?

Interactions that occur when one drug alters the pharmacological effect of another at the receptor site.

What is physical dependence?

A condition where chronic drug use produces tolerance and withdrawal symptoms.

What is tolerance?

The need for more drug to produce the same response due to chronic use.

What is withdrawal?

Physical symptoms that occur upon abrupt discontinuation of a chronically used drug.

What does it mean if a receptor for a substance exists?

It means there is an endogenous ligand that will bind that receptor.

What is the difference between dependence and addiction?

Dependence refers to physical and psychological reliance on a drug, while addiction is a more severe condition characterized by compulsive drug-seeking behavior.