Definitions Flashcards
Pharmacology
The study of the effect of drugs on the function of living systems
Pharmacodynamics
The effects of the drug on the body
Pharmacokinetics
Effects of the body on the drug, comes in 4 steps
1) Absorption
2) Distribution
3) Metabolism
4) Excretion
Drug
Biologically active compount other than a nutrient or essential dietary ingredient, consumed with the intent to produce a change in the body
Medicine
A chemical preparation which usually contains one or more durgs administered with the purpose of producing a therapeutic effect. Usually contain other substances to make them easier to use
Transgenic Models
Models that show changes in genetics that ace a random gene inserted into its DNA ie A normal rat with a rat that has been modified
Bioavailability
The fraction of administered dose that reaches the systemic circulation
- Incomplete bioavailability can be due to:
+ Incomplete absorption
+ 1st pass metabolism, where the drug passes through the system completely
Enteral administration
Where drugs are absorbed by GI tract Administration routes includes: - Oral - Sublingual - Rectal - Inhalation
Topical administration
Where drugs are applied directly on Administration routes includes: - Skin - Epithelial surfaces - Mucosal
Parenteral administration
Non-oral methods of drug administration ie injections Administration routes includes: - Subcutaneous - Intramuscular - Intravenous - Intrathecal
The apparent volume of distribution (Vd)
Defined as the volume of fluid required to contain the toal amount of the drug in the body at the same concentration as that present in the body
Vd = D/Cp
Vd = Volume of Distribution D = The total amount of drug in body Cp = Blood concentration
Vd cannot be less that the physiological volume of intravascular plasma (approx. 3L)
Can be further divided by body weight to normalise
Prodrugs
Where metabolism takes the parent compound + makes it metabolically active pharmacologically
1st Pass Metabolism
When metabolism begins before drugs reach general circulation/drug target
receptor Occupation Theory
Generally, the drug with the higher affinity is more specfiic for that receptor
Dissociation Constant Equation
Dissociation Constant = Rate of dissociation/Rate of association
Association constant
Association Constant = Rate of association/Rate of dissociation
Ki
Defines as the concentration of competing ligand required to displace 50% of the specific binding of the radiolignad + gives an estimate of affinity in assays
EC50 (Half Maximal Effective Concentration)
The concentration of a drug that causes 1/2 the maximal effect produced by a particular drug, not a measure of efficacy, a measure of potency of an agonist, but not a measure of affinity. Also gives infoIC50 about drug selectivity
IC50 (Half Maximal Inhibitory Concentration)
Concentration of antagonist required to block agonist response, dependent on assay conditions used. Approximates affinity of competitive reversible antagonists, but doesn’t tell the mechanism of the antagonist
Dose ratio
Dose ratio = EC50 + Antagonist/EC50 control
EC50 control is just the agonist concentration
The Schild Plot
Tells if the an antagonist is competitive and if so, an estimate of its affinity
Phase 1 reactions
- Such possible reactions are to change the drug molecule structure including
+ Oxidation
+ Reduction
+ Hydrolysis
Phase 2 reactions
- Involves formation of covalent bonds
- Results in water-soluble conjugates for excretion
- Products of phase 2 are predominantly inactive however in some cases activity is retained
1st pass metabolism
- Where metabolism begins before the drug reaches general circuit/drug target
- Can be caused by:
+ Liver
+ Lung
+ Intestinal lumen
+ Intestinal wall
