Lecture 1 Pharmacology Flashcards
4 stages of Pharmacokinetics
- Absorption
- Distribution
- Metabolism
- Elimination
Absorption
- Drugs are made available to the body fluids that distribute the drugs to organ systems
- Passive: high to low
- Active: low to hight
What are the 2 key factors in absorption
- route of a administration
- dosage formulation
Bioavailability
- Measurement of completeness of absorption
Enteral Administration of Absorption
- Oral: first pass effect, taken by mouth, subject to liver and GI system
- Buccal: between gum and the inner lining of the mouth cheeks
- Sublingual: not subject to first pass by liver, taken under tongue
- Rectal: Good blood and lymph supply, fast-acting, easy distribution
Parenteral Administration of Absorption
- Transdermal: through skin administration, Iontophoresis and phonophoresis
- Topical: Applied directly to skin, Steroid Cream, numbing creams
First pass effect
- only applies to ORAL MEDS
- Absorbed in the alimentary canal
- Transported to the liver through the portal vein
- Dosage must be large enough to survive first pass effect
- Liver metabolizes drugs
Controlled Release Preparations
- Can be Timed, extended, sustained release
- Slow, uniform dissolution of the drug so that more drug can reach the systemic circulation
-Less doses per day, more sustained levels
Enteric-coated or delayed release formulations
- resist stomach acid
Distribution
- movement or transport of a drug to the site of action
Distribution depends on which 4 factors
- Tissue Permeability
- Blood flow
- Binding to plasma proteins
- Binding to subcellular components
Distribution: Tissue Permeability
- highly lipid soluble drug can pass through easier
- Blood-Brain Barrier: filters selectively to protect CNS (limiting the substances that enter the brain and spinal cord)
- Morphine: across the BBB to act on CNS itself
Distribution: Blood Flow
- Better Blood flow = Better distribution
- Drugs circulating in the bloodstream will gain greater access to perfused tissues
- Disease can reduce blood flow, leading to less drug being delivered to tissues
Distribution: Binding to plasma proteins
- Drugs form reversible bonds to circulating proteins
- only the unbound or “free” drug can reach target tissue and have effects
- Bound drug not available for therapeutic effect
Distribution: Binding to subcellular components
- Drugs bound to specific intracellular components can not take effects or be distributed
- Subcellular organelles can trap the drug within the cell
Other factors affecting distribution
Competition between medications for the same receptors
Metabolism: Biotransformation
- Biotransformation: chemical changes that take place after taking a drug
- Metabolite: altered version of the original compound, usually inactive or reduced level of activity
What is the primary function of biotransformation
- drug termination
Primary Biotransformation location
- Liver
others include: lungs, kidneys, skin, GI epithelium
Metabolism: Enzyme Induction
- prolonged use of medication leads to reduced effects and higher tolerance, because body is adjusting to it
Tolerance
- Repeated same dose produce a lower response, so needs to increase amounts of a drug
- often seen with Narcotic/ Analgesics
Primary sites for drug excretion
Kidneys
Gomerular filtration
drugs are filtered through the glomerulus and then carried through the tubule into the urine
Polar vs. nonpolar compound
- Polar: cannot be diffuse back into circulation
- nonpolar: can be reabsorbed back into system
- drugs that bind to plasma proteins will remain to circulation; not bound will be excreted
