Class 3 - Pharmacology Flashcards
What are the 4 processes of pharmacominetics?
1 . Absorption
2. Distribution
3. Metabolism
4. Excretion
Absorption
The movement of a drug from the site of administration to the blood
Distribution
- Movement of the drug from the blood to interstitial space of tissues and enter the cell
- It is determined by 3 major factors: blood flow to tissues, the ability of a drug to exit the vascular system, and the ability of a drug to enter cells
Metabolism
- To be excreted by kidneys
- Some drugs act on specific liver enzymes to increase rate of metabolism (inducers) –> the plasma levels fall and its therapeutic effect is reduced
- Others decrease metabolism (inhibitors) -> when metabolization is inhibited, drug plasma levels stay high, increasing the effect of the drug… toxicity
First pass effect
When drugs are absorbed from the GI tract and immediately pass through the liver resulting in significant inactivation of the drug and limiting its therapeutic effect
What are the 6 possible consequences of drug metabolism
- Accelerated excretion from the kidneys
- Inactivation of the drug
- Conversion of a “prodrug” to its active form
- Increased therapeutic action
- Increased toxicity
- Decreased toxicity
Excretion
- The kidneys excrete the majority of drug
- Drugs can also be excreted through secretion in bile and then excreted in the feces, through the lungs, and in the sweat glands, saliva and breast milk
Ionization rule
- Nonionized drugs = lipid soluble –> absorbed (can cross BBB)
- Ionized drugs = water soluble –> excreted (travel through pores in capillaries)
Protein binding in drugs
ALBUMIN
- All drugs have this property
- Reversible
- A drug that is highly protein bound may take longer to develop a plasma concentration
Half-life
The time required for the plasma level of the drug to decrease by 50% after administration
- Determines the dosing interval
How many half-lives to hit therapeutic range?
To hit a steady state in the plasma it takes 4 half-lives
What are the 4 families of receptors that drugs act on
- Cell membrane-embedded enzymes
- Ligand-gated ion channels
- G protein-coupled receptor systems
- Transcription factors
3 ways drugs can affect receptors
- Agonist
- Antagonist
- Partial agonist
Agonist
By activating or mimicking the receptor’s activity
Antagonist
Block/prevent the action of endogenous regulatory molecules
- Non-competitive vs Competitive
Partial anatgonist
They are used to produce modest effects and to minimize adverse effects that can result from full activation of the receptor
Maximal efficacy
- The biggest effect a drug can produce
- The goal is to match the drug’s maximal efficacy with the intensity of the patient’s needs
Potency
The amount of a drug need to produce an effect
Altered metabolism
CYP450 liver enzyme system
- Enzymes induced by Drug A –> Drug B effects reduced
- Enzymes inhibited by Drug A –> Drug B effect increased
Lab values
- Kidney = SERUM CREATININE
M (53-106 mcmol/L); F (44-97 mcmol/L)
– Increased level = kidney impairment
– Decreased level = decreased muscle mass - Liver = LIVER FUNCTION TESTS (AST/ALT)
- Electrolytes = SODIUM AND POTASSIUM
S (135-145 mmol/L); P (3.5-5 mmol/L)
– Some drugs will increase levels and other drugs ill decrease levels
