Use LEFT and RIGHT arrow keys to navigate between flashcards;
Use UP and DOWN arrow keys to flip the card;
H to show hint;
A reads text to speech;
19 Cards in this Set
- Front
- Back
Biopharmaceutics:
|
*Factors related to the dosage form that affect the rate and extendt of drug reaching the systemic ciculation and ultimately the site of action.
|
|
Pharmacokinetics:
|
*The use of mathematics to characterize and predict drug disposition in the body.
|
|
Drug disposition:
|
*The sum total of processes that a drug undergoes once in the body. ADME
Absorption Distribution Metabolism Excretion |
|
Absorption:
|
*The process required for drug to get from the site of administration into the plasma (SYSCIR)
|
|
Distribution:
|
*As the drug circulates in the SYSCIR, it localizes preferentially in certain tissues (the drug "distributes" to certain tissues)
**If the drug has a higher tendency to locate in tissues, it is "HIGHLY DISTRIBUTED" **If the drug has a higher tendency to stay in the plasma, it is NOT highly distributed. |
|
Metabolism:
|
*The process of enzymatic conversion of drugs into metabolites
|
|
Excretion:
|
*The sum total of processes that remove a drug from the body.
**Urinary excretion **Fecal elimination **Sweating **Exhalation |
|
Zero order
|
Elimination Rate: Constant, does not depend on amt/conc of drug present
**Review equations |
|
First Order
|
Elimination Rate: varies depending on amt/conc of drug present **Review equations
|
|
Why do pharmacokinetics?
|
*Want drug to be effective with min. or no SEs:
-need a threshold amount of drug molescules present at the drugs receptor at the site of action (usually in tissues) -Too many drug molecules at the site of action or at unintended sites in the body can lead to toxic effects or unwanted effects **Most of the time the concentration of drug in the tissues is proportional to (or linearly related to) the concentraion of the drug in the plasma |
|
Why do pharmacokinetcs?
|
Example: Digoxin
*treats CHF; intended site of action is in the heart. *taken orally, dig is absorbed into the plasma and circulates throughout the body -As it circulates, dig is distributed into tissues, including heart tissue -therefore, as plasma concentration of dig increases, tissue concentraion of dig increases as well |
|
Continued:Digoxin
|
*Dig has a narrow therapeutic index (narrow range of tissues concentrations for which dig is therapeutically effective w/o causing SEs)
-Dig SEs are not trivial and can be harmful -Can't biopsy heart tissue to determine dig concentraion at site if action -Next best thing: measure plasma concentration levels of the dig -Because tissie concs are proportional to plasma concs, can determine plasma concs for which dig is therapeutically active w/o being toxic or causing SEs |
|
Continued why do pharmcokinetics??
|
*Take it a step further:
--Can find therapeutci ranges by experimentation using a population sample --Use average range to predict appropriate plasma concentraions (and this appropriate dose) --Once dose is given, PK allos us to monitor plasma concentraions and adjust the dose accordingly --PK allow pharmacists to tailor dosage regimens specifically for particular pts |
|
PK models:
|
*Allow us to visualize the course of the drug in the body by representing the body as a series of compartments
*Each "compartment" represents a tissue or group of tissues that have similar blood flor and drug affinity *Each compartment will be similar in terms of: -Drug distribution to the compartment -Drug conc in that comparntment; and -Drug elimination from that compartment *Allows us to visualize how drugs enter the compartment and how drugs are eliminated from the compartment |
|
One Compartment Model, IV bolus:
|
*Simplest Model: One compartment with IV bolus injection of drug
-Drug is located in one compartment of the body, the "Central Compartment"! |
|
Central Compartment:
|
*Plasma and tissue that are highly perfused=receives a high amount of blood flow to the tissue
*Drug conc equilibrates rapidly in tissues that are highly perfused *Examples of tissues that are part of the central compartment:: ***Heart, kidneys, lungs, liver |
|
1 compart, IV bolus:
|
*Iv bolus, therefore essentially all of the drug is in the plasma at the time of injection (t=0)
*One compartment because drug is not higly distributed to tissues outside the central compartment *That is, there would not be any significant conc of drugs in any other tissues besides heart, kidney, lungs, liver |
|
One compartment Model, First Order Absorption:
|
*One compartment, so drug is not distribued significantly outside the central compartment
*Instead of IV bolus admin., drug must be absorbed from a site of administations *First order absorption occurs with any formulation that reqires an absorption step: ex. po transdermal ( not CR), IM, SQ |
|
Two Compartment Model, IV Bolus:
|
*IV bolus, therefore essentially all of the drug is in the plasma at the time of injection (t=0)
*Drug distributes from the plasma and tissues of the central compartment to other tissues *Elimination of drug occurs ONLY from the central compartment |