What happens after a drug has been administered
Terms in this set (42)
What is pharmacokinetics?
an area of pharmacology dealing with how drugs move throughout the body.
What are the four components or processes of drug transport?
absorption, distribution, metabolism, and excretion
What is the process of absorption?
the first step in how the body handles a drug; process involving the movement of a substance from its site of administration across one or more body membranes. Drugs cross many membranes before reaching target organs. Many factors affect absorption.
What is the process of distribution?
the second step in how the body handles a drug; process by which drugs are transported after they have been absorbed or administered directly into bloodstream. Drugs bound to plasma proteins may be isolated in the plasma and prevented from reaching their target cells.
What are three anatomic barriers that represent areas in the body where drug distribution may be limited and prevent some drugs from gaining access?
The blood-brain barrier, the blood-placental barrier, the blood-testicular barrier.
Which anatomic barrier serves an important protective function in pregnant women?
The blood-placental barrier because it regulates which substances pass from the mother's bloodstream to the fetus.
What is metabolism?
the third step in how the body handles a drug; the sum total of all chemical reactions in the body or an organ. Metabolism occurs in almost every cell and organ - including the intestinal tract and kidneys, but the liver is the primary site.
What is biotransformation?
the chemical conversion of drugs from one form to another that may result in increased or decreased activity.
Why is metabolism important to drug therapy?
because chemical reactions deactivate most drugs.
Why do patients with liver disease usually receive much lower doses of drugs than normal?
because their liver is unable to metabolize the drug to a safe, active form.
What are prodrugs?
drugs that require metabolism to make them active. As the drug is broken down by chemical reactions of metabolism, the products formed by the breakdown produce a more intense response than does the original drug.
What is the first-pass effect?
a mechanism whereby drugs are absorbed across the intestinal wall and enter into blood vessels, known as the hepatic portal circulation, which carries blood directly to the liver (for metabolism). The liver may then metabolize the drug to a less active form before it is distributed to the rest of the body and target organs. In some cases, the first-pass effect inactivates more than 90% of an orally administered drug before it can reach general circulation.
What is excretion?
the fourth and final step in how the body handles a drug; the process of removing substances from the body by urination, exhalation, defecation, and/or sweating. Drugs are normally removed from the body by the kidneys, the respiratory tract, bile, or glandular activity.
What is the main organ of excretion?
What is a difference in respiratory excretion, in contrast to other methods of excretion?
the lungs excrete most drugs in their original unmetabolized form.
What is enterohepatic recirculation?
recycling of drugs and other substances by the circulation of bile through the intestine and liver
What does the term rate of elimination mean?
refers to the amount of drug removed per unit of time from the body by normal physiologic processes.
What does the rate of elimination help to determine?
how long a particular drug will remain in the bloodstream and is thus an indicator of how long a drug will produce its effect.
What is half-life of a drug?
the length of time required for a drug to decrease its concentration in the plasma by one half of the original amount.
How does renal or hepatic disease affect half-life of a drug?
the plasma half-life increases, reflecting the important relationship of half-life to metabolism and excretion.
What is pharmacodynamics?
how the drug exerts its effects; the study of how the body responds to drugs and natural substances
What is the receptor theory?
a classic theory referring to the cellular mechanism by which most drugs can change body processes.
What is a receptor?
any structural component of a cell to which a drug binds in a dose-related manner to produce a response.
Where in the body can receptors be located?
on the plasma membrane or in the cytoplasm or nucleus of the cell
What terms are often used to describe drug action at the receptor level?
agonist and antagonist
What are Agonists?
drugs capable of binding with receptors and causing a cellular response; these are FACILITATORS of cellular action. When they are present in the bloodstream, agonists cause the tissue to respond, resulting in a therapeutic action.
What are Antagonists?
drugs that inhibit or block the responses of agonists. Antagonists are called BLOCKERS.
What terms are often used to describe the success of drug therapy?
potency and efficacy
What is potency?
refers to a drug's strength at a certain concentration or dose.
What is efficacy?
refers to the ability of a drug to produce a more intense response as its concentration is increased; the ability of the medication to bring essential relief
Patients with liver disorders would most likely have problems with which pharmacokinetic phase?
What is a principle of drug-receptor interaction?
must occur at its target tissue
What are drugs called that bind with a receptor to produce a therapeutic response?
In pediatric and elderly patients, why is drug dosing decreased?
reduced metabolic enzyme activity
Is absorption generally faster across thinner or thicker membranes?
What are factors that influence the success of drug therapy?
drug dosing, frequency of dosing, and a changing medical condition
What is the process of moving a drug from its site of administration across one or more body membranes called?
What process describes how drugs are transported in the body?
What is the term used to describe how much of a drug is available to produce a biological response?
What is the removal of larger drug metabolites from the bloodstream to the urine referred to as?
For drugs easily dissolved in bile, a fraction of the drug amount is eliminated from the body through what?
What is important regarding excretion mechanisms and the breasts?
drugs excreted into breast milk may significantly harm the nursing infant.