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37 Cards in this Set

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What is pharmacokinetics?
refers to the time-course of drugs and their metabolites in various tissues of the body. It is based upon concepts of drug disposition, that is, the fate of drugs in the body with regard to drug entry (or absorption), distribution, biotransformation (or metabolism), and elimination. Pharmacokinetics may be considered “what the body does to the drug."
What is pharmacodynamics?
refers to the relationship between drug levels in the body and the pharmacologic effects of drugs. Pharmacodynamics may be considered “what the drug does to the body.”
What are drug receptors?
may be enzymes, cellular mediators, proteins, or other structures or organs or membranes
What is a therapeurtic range? What are two of the defining characteristics?
The minimum effective concentration and maximum safe concentration define the therapeutic range. It should only be viewed as an initial guide to therapy. Some patients may be below the minimum and some patients can take levels of the maximum recommendation.
can be narrow or wide, depending on the pharmacological effects.
What is the best way to measure drug efficacy and drug toxicity?
CAN ONLY BE DETERMINED BY CLINICAL ASSESSMENT of the patient's drug response. This is why it is important to define MONITORING PARAMETERS for drug beneficial effects and drug toxic effects.
What is bioavailability?
-describes the extent of drug entry into the systemic circulation and is defined in reference to direct IV drug administration, where the extent of drug entry is considered to be 100%.
What is the rate of bioavailability?
The rate of bioavailability refers to the speed with which a drug is available to the system circulation. The rate of drug bioavailability varies from rapid (within minutes) to moderate (within a few hours) and slow (requiring six or more hours).
How does large/small volume of distribution explain drug distribution in tissues?
-drugs with a large volume of distribution distribute extensively into extravascular tissues
-small volume of distribution do not
What is first-pass effect? What organ does it involve? Does it usually involve oral, IV, or SC drugs?
-refers to the strategic location of the liver in the venous portal pathway between the gut and system circulation. Drugs given orally and well absorbed in the gut must first pass through the liver before entering into the arterial circulation. When the liver has a high affinity and high metabolizing capacity for a drug, it may remove and metabolize substantial amounts of the drug during this “first- pass” of the drug through the liver. This effectively reduces the drug’s extent of bioavailability. The first pass is so effective for some drugs that they cannot be administered by the oral route.
What does biotransformation of a drug refer to?
- the metabolism of the drug!
-more specifically the alteration of a drug by the body to one or more chemically different species, or drug metabolites
What three important clinical pharmacokinetic aspects of drug actions can biotransformation impact?
1.extent of bioavailability,
2.drug elimination
3. clinical effects of active metabolites.
What is drug elimination half life (t1/2)?
-time required for the drug level to decline by 50%
-important in decisions about proper dosing interval for medications
What is the steady state of a drug?
-when the rate of drug entry equals the rate of drug elimination
How many half lives does it take to reach steady state?
How many does it take to eliminate the drug?
-4-5 half lives to reach steady state and 4-5 half lives to eliminate the drug
What is cytochrome p450?
-generic name for the group of enzymes that are responsible for most drug metabolism reactions.
-included are CYP1A2, CYP2C9, CYP2C19, CYP2D6, CYP2E1, CYP3A4.
What is a drug delivery system?
formulation or device that safely brings a therapeutic agent to a specific body site at a certain rate to achieve an effective concentration at the site of drug action.
What is drug delivery system used for?
- to carry, distribute or transport drugs into and throughout the body
What is a pro-drug?
-form of a drug that remains inactive during its delivery across biologic membranes or until it reaches the site of action.
-In other words, a pro-drug is an inactive precursor of a drug.
What are the benefits of a pro drug?
Increase solubility or absorption
-increase chemical and metabolic stability
-mask irritation or taste
What are the three main functions of the Blood brain barrier?
1) it protects the brain from “foreign substances” in the blood that may injure the brain
(2) it protects the brain from normal hormones and neurotransmitters of the rest of the body
(3) it maintains a constant environment for the brain.
How do drugs enter the body directly?
injection into body fluids such as
-blood (IV)
-cerebrospinal fluid (intrathecal administration)
How do drugs enter the body indirectly?
-absorption across membrane barriers of the
-GI tract(oral)
-skin (transdermal)
-Muscle (IM)
-pulmonary alveoli (inhalation)
What are important determinants of the rate and extent of indirect drug entry into the body?
1. physical formulation of the drug
2. biophysical properties of the drug
What are types of drug formulations?
-rapid entry
-a tablet for moderate entry
-time release preparation (slow entry)
What are physical properties that affect entry into the body?
-biophysical properties
1.molecular size
2. liphophilicity
3. acid/base characteristics
What factors determine the distributional properties of a drug?
1.molecular size
2. lipophilicity
3. acid/base properties
4. affinity to bind to circulating and tissue protiens
What are two ways biotransformation contributes to drug elimination?
o First, biotransformation may convert a lipophilic substance to a water soluble form which is more readily excreted in urine or bile than is the original drug.
o Secondly, biotransformation to a pharmacologically inactive metabolite effectively eliminates the original drug from the system insofar as its pharmacodynamics are concerned.
What patient factors influence drug effects in the body?
1. body size
2. body composition
3. sex
4.age
5. lifestyle habits (smoking)
What three general factors influence drug effects?
1. patient factors
2. diseases
3. concurrent drug therapy
How do diseases effect drug effects on the body?
Diseases that affect organ function can significantly influence drug disposition and may have a sizable influence up on the patient’s clinical response to a given dosage regimen.
- Since the liver and the kidney are the primary organs involved in drug biotransformation and elimination, it is not surprising that disease affecting these organs must often be taken into account in dosage regimen design.
-- Renal disease may influence both dose used and the interval with which it is administered. Hepatic disease (cirrhosis, acute hepatitis, etc.) may have similar effects on regimen design for some drugs.
How does concurrent drug therapy effect the drug effects in the body?
may alter drug disposition in a predictable fashion
What is linear pharmacokinetics?
-Most drugs follow linear pharmacokinetics in which steady state serum concentrations change proportionally with long-term daily dosing.
How does a linear pharmacokinetic drug effect the steady state if the dose is doubled?
- a patient who doubles the dose of a medication will have a doubling of the steady state serum concentration of that drug.
What is non linear pharmacokinetics?
Instead of steady state drug concentrations changing proportionally with the dose, serum concentration changes may be more or less than expected.
How does a non linear drug effect the steady state if the dose is doubled?
-if a practitioner doubles the dose of a drug following non-linear pharmacokinetics, the steady state serum concentration of the drug could quadruple with corresponding pharmacological effects and potentially toxicities, too.
What is a targeted drug delivery system? When would you use it, and what are the benefits?
-delivering drugs to a desired body location, organ, tissue, specific cells, intracellular organelles, or molecules
-it is used to optimize a drug's therapeutic index by strictly localizing its activity to the site or organ of action
- results in a significant limiting of drug toxicity, a reduction in the dose of the drug, and an increased efficacy of treatment
What is controlled drug release? When would you use it and what are the advantages of its use?
-the release of a drug or other active agent in a predesigned manner
-rationale is to promote therapeutic benefits while at the same time minimizing toxic effects
-Controlled, sustained drug delivery can reduce the undesirable fluctuations of drug levels, enhancing therapeutic action and eliminating dangerous side effects.