Chapter 4 Flashcards
what are the 4 phases of pharmacokinetics?
Absoprtion
Distribution
Metabolism
Excretion
What are the 3 ways that drugs cross a cell membrane?
- Passage through channels or pores
- passage with the aid of a transport system
- Direct penetration of the membrane itself.
In order for a drug to have effect, it needs to ___
enter a cell
In order for a drug to cross a cell membrane, what property do they need to posess?
Lipophilic
- lipid soluble
elimination: ___ + ___
metabolism + excretion
the most importan transporter protein that takes drugs out cells is:
P Glycoprotein
Define: Absorption
the movement of a drug from its site of administration into the blood.
the ___ of absorption determines how ___ effects will begin.
rate, soon
the rate of dissolution helps to determine the rate of ___
absorption
Absorption depends on these: (5)
- Rate of dissolution- dissolving in stomach/intestines
- Surface area- larger surface area: ^ absorption
- Blood flow- ^ then absorption is fast
- Lipid solubility- ^ absorbed faster, low absorbed slow
- pH partitioning- basic is attracted to acidic
the routes of administration that are the most commonly used are:
- enteral (GI tract)
2. Parentaral ( Outside the GI tract- injection)
The principle paranteral routes of med administration are:
- intravenous
- subcutaneous
- intramuscular
the route by which a medication is administered will significantly effect both the ___ and the ___ of effects
onset, intensity
IV medication administration:
- no barriers to absorption: straight into blood
- Complete and instantaneous ( no first pass effect)
- Advantages: rapid onset, control of dose, ^ fluid volume dose, can use irritant drugs bc its diluted
- Disadvantages: ^ cost, difficult, inconvenient, IRREVERSIBLE ONCE GIVEN, infection, embolism
You should take at least ____ to administer IV drugs
1:00 minute
How can IV insertion create an embolism?
- damage to the venous wall, creating thrombus
- Injection of hyper and hypotonic solutions can destroy RBC’s. debri from these cells can make embolism
- powder drug not shaken enough
IM medication administration:
- barrier: capillary wall
- absorption: depends on water solubility & blood flow
Advantages: can be used for admin of poorly soluble drugs, depot preparations (depo privara birth control shot)
Disadvantages: Hurts, inconvenient, local tissue injury, possible nerve damage, bleeding risk for those on anticoagulants
Subcut medication administration:
- barrier: pass through spaces between cells of the capillary wall
Advantages: same as IM
disadvantages: same as IM
Oral medication administration:
- barriers: layer of epithelial cells, capillary wall
- Absorption: highly variable due to many factors…
Advantages: easy, convenient, inexpensive, safer
Disadvantages: variability, inactivation, local irritation, patient responsibility
Factors that influence absorption of Oral medications: (6)
- solubility and stability of the drug
- gastric and intestinal pH
- gastric emptying time
- food in the gut
- coadministration of other drugs
- special coating on the drug
Enteric coasted oral preparations protect what? (2)
- drug from acid and pepsin in stomach
2. stomach from drug that cause cause gastric discomfort
defined as drug movement from the blood to the interstitial space of tissues and from there into the cells
distribution
Distribution is determined by 3 major factors:
- blood flow to tissues- except abcess & tumors
- the ability of a drug to exit the vascular system
- the ability of drugs to enter the cell
drugs that are bound to albumin have an extended:
half-life and distribution phase
Drug metabolism is also known as ___ and is defined as__
biotransformation,
the chemical alteration of drug structure
what performs the metabolism of drugs in the liver?
Hepatic Drug- Metabolizing Enzymes: Cytochrome P450 system (CYP)
the most important consequences of drug metabolism is:
promotion of renal drug excretion
in infants, drug metabolism capacity is limited, why?
bc their liver doesn’t develop fully until their 1 yr old.
The first-pass effect refers to:
the rapid hepatic inactivation of certain oral drugs.
If the capacity of the liver to metabolize a drug extremely high, that drug can be ___
completely inactivated on its first pass through the liver.
“First Pass Effect”
if renal failure occurs, both the ___ and ___ of drug responses may occur.
duration and intensity
Urinary excretion of drugs occurs from 3 processes in kidney:
- glomeruluar filtration
- passive tubular reabsorption
- active tubular secretion
Non renal excretion of drugs:
breast milk (only lipid soluble drugs can exit)
Bile- pooped out or reabsorbed through portal blood
Lungs- volatile anesthetics
Small amounts in sweat and saliva
For most drugs, there is a direct correlation between ___ and __ responses and the ___ of drug present in the plasma
therapeutic and toxic responses and the amount of drugs present in the plasma
Minimum Effective Concentration (MEC)
the plasma drug level below which therapetuci effects will not occur.
the plasma level which toxic effects begin
toxic concentration
range of plasma drug levels that fall between the MEC and toxic concentration:
therapeutic range
the objective of drug dosing:
maintain plasma drug levels within the therapeutic range
Drug Hal-Life
time required fro the amount of drug in the body to decrease by 50%
the drug ___ determines the dosing interval
half life
when the amoutn of drug eliminated between doses equals the ______, average drug levels will remain constant and plateau
doses administered
if doses remain constant, plateau will be reached in ____
4 half-lives
What are 3 techniques to reduce fluctuations in drug levels?
- administer drugs by continuous infusion
- administer a depot preparation
- reduce both the size and dosing interval of each dose
