What are the four processes of Pharmacokinetics?
Determines how much of an administered dose gets to it's site of action.
4 major phases:
1. Drug Absorption
2. Drug Distribution
3. Drug Metabolism
4. Drug Excretion
This process is "the impact of the body on drugs" & How Drug moves through body.
Movement of drug from administration site into the blood stream.
The rate depends on route of administration
- speed of dissolving
- Surface area
- blood flow
- lipid solubility
- Drug concentration
Movement of drug through the blood stream to tissues and cells
- Blood Flow
- Drugs ability to leave blood (protein binding; BBB, Placental Membrane)
- Drugs ability to enter cells
Conversion of the drug into another substance; also called biotransformation
sites for drug metabolism:
- Liver (primary location); GI Tract; Lungs, Kidneys, Skin
Factors affecting Metabolism:
- Liver Function; life span/gender; lifestyle; habits; diet; environment
Removal of drug or the substance it became from the body;
Routes of excretion:
- Urine (most common)
- Exhaled thru lungs
- breast milk
The rate at which drug molecules disappear from the circulatory system, primarily through hepatic (liver) metabolism and renal (kidney) excretion.
Process during distribution in which a portion of drug is attracted to & binds to protein, such as albumin in blood, preventing it from passing through capillary walls; therefore this portion is inactive and cannot achieve therapeutic effect.
The portion of being distributed in the body that is not bound to protein and therefore is active and can achieve therapeutic effect.
Impact of drugs ON the body
Biological, chemical, and physiological actions of a particular drug within the body & study of how those actions occur.
How a drug causes the changes in the body (once at receptor site- what is the drug doing? blocking receptors)
Drugs CANNOT create new responses in the body, can only turn on, turn off, promote, or block a response that the body is already capable of producing.
Drug molecule that attach to receptors on cells to stimulate the cell to act; they promote function
Drug molecules that attach to receptors and prevent something else from attaching (block the receptor) and causing effect.
The amount of time that is required to remove half (50%) of the blood concentration of a drug.
The point at which the amount of drug that is administered and the amount that is being eliminated from the body balance off. The balance creates a stable level of drug in blood.
achieved @ 4-5 half lives
increasing does does NOT affect it, only based on time it takes for 4-5 half lives to occur.
Clearance ( or clearance rate)
the rate at which drug molecules disappear from the circulatory system, primarily through hepatic (liver) metabolism & renal (kidney) excretion.
Gender can alter too
Another term for metabolism of drugs; when drugs are changed from their original form to a new form in the body.
A product of metabolism, a drug that is metabolized and is generally changed into an inactive form on its way to excretion. Occassionally a drug can be metabolized into an active metabolite (substance) that can achieve an independent effect that can be either therapeutic or cause adverse effects.
drugs that are inactive until metabolized into an active form.
First Pass Effect
The rate of metabolism of a drug varies as it is circulated through the blood stream, to portal circulation and through the liver. If the percentage of the drug metabolized on the first circulation or pass through the liver is high (highly metabolized) then the drug losses effectiveness during this "First Pass'' before it reaches the general circulation (Loss of effectiveness in first pass)
A system of liver (microsomal) enzyme families, (also called cytochromes), three of which are involved in drug metabolism. Drugs can either induce or inhibit the P-450 system altering metabolism of other drugs.
A drugs relative pharmacologic activity; the amount of drug that must be given in order to produce a particular response. (Highly potent drugs often have affinity for the receptor site on the cell so little is needed to produce its effect.)
PP: Amount of drug that must be given in order to produce a particular response.
How well a drug produces its desired effect; it is related to its intrinsic activity; the higher the activity, the greater the efficacy.
PP: The level of the drug and how well a drug produces its desired effect.
Minimum Effective Concentration
This is the goal for amount of drug!
Effective Dose 50 the dose of a drug that is required to produce a therapeutic effect in 50% of the population. Often considered the standard or typical dose and is chosen when the drug therapy is initiated.
Lethal Dose 50 the point at which the dose of a drug would be fatal in 50% of the population.
A drug that is administered consistently over time, such as every day. (often achieved after 4-5 half lives)
A higher dose of a drug given initially at the start of drug therapy when the drug has a longer half life and needs to achieve steady state in shortened time frame to the patients' medical condition requiring immediate steady state for effective treatment.
PP: Difference b/w a Effective Dose and a Lethal Dose.
A ratio of comparison used to determine the safety of a drug. The ED50 is divided by the LD50 in ratio form and if there is little difference b/w the two the drug has a narrow therapeutic index and is therefore not very safe due to difficulty in dosing the drug safely (also called therapeutic range)
An immune system, antigen/antibody response after a drug is taken again,. It involves the release of hisamine, which leads to allergic s/s and possible anaphylaxis; the most serious allergic response
An unusual adverse effect of a drug; can be an opposite response from what is anticipated. An individuals unique response to a drug, also called a paradoxical effect.
When 2 or more drugs that are alike in therapeutic effect are combined and the resulting response is the sum of the drugs effect. (can be intentionally, more therapeutic or unintentionally can cause harm)
When 2 or more unlike drugs (in terms of therapeutic effect or mechanism of action) are used together to produce a combined effect; the outcome response is greater than if either was used alone
An interaction between drugs in which one of the 2 drugs is increased. ie a drug that has a mild effect may enhance the effect of a second drug
Is the opposite of a synergistic effect which results in a therapeutic effect that is less than the effect of either drug alone bc the second drug either diminishes or cancels the effects of the first drug.
Anything that can harm a developing fetus or cause a birth defect (the majority of drugs can be teratogens)