Stressors Requiring Medication Phases of Drug Action. NUR101 Fall 2009 Lecture # 11 & 12 K. Burger, MSEd, MSN, RN, CNE PPP by Sharon Niggemeier RN, MS (J. Garnar & R. Kolk) Rev kburger06,07. Three Phases of Drug Action. I. PHARMACEUTICAL PHASE II. PHARMACOKINETIC PHASE
NUR101 Fall 2009
Lecture # 11 & 12
K. Burger, MSEd, MSN, RN, CNE
PPP by Sharon Niggemeier RN, MS
(J. Garnar & R. Kolk) Rev kburger06,07
I. PHARMACEUTICAL PHASE
II. PHARMACOKINETIC PHASE
III. PHARMACODYNAMIC PHASE
3# Metabolism (Biotransformation)
Liquids, elixirs, syrups FastestSuspension solutions êPowders êCapsules êTablets êCoated tablets êEnteric-coated tablets Slowest
Mucous membranes of the mouth:
intraarticular - synovial cavity
intrathecal - spinal subarachnoid space or epidural space
REMEMBER – Parenteral meds retain 100% bioavailability THEREFORE smaller doses are appropriate
Volume of Distribution (Vd) - The degree of distribution of a drug into various body compartments and tissue
PlasmaProtein Binding - drugs bind to proteins in the blood (albumin, globulins) in varying degrees, from highly bound to poorly bound
Protein binding decreases the concentration of free drug in circulation therefore there is a limited amount of drug available to travel to the site of action. Only free drug is able to diffuse into tissues.
Only free drug is able to diffuse into tissues, interact with receptors, and produce biological effects. Bound drugs are pharmacologically inactive.
Excretion: process where drugs are removed from the body. Kidneys are the major organs of excretion.
Lungs excrete gaseous drugs.
Biliary excretion (bile & feces) is important for a few drugs. These drugs may be reabsorbed when passing through the intestines from the liver ( enterohepatic re-circulation).
Intestines, sweat, saliva and breast milk constitute minor routes of drug excretion.
Clearance of drugs - elimination of drugs from circulation by all routes. It affects the time a drug remains in the body and the dosage required.
Trough level will occur immediately before a drug is given, or once sufficient drug is eliminated. This is the lowest point of drug concentration
Plasma blood levels may be taken for peak and trough levels. The drug must be administered precisely as ordered and a blood sample must be taken just before the next drug dose is scheduled for an accurate trough level.
Therapeutic range: plasma drug concentration between minimum and toxic concentrations.
Loading doses: higher amount of drug given once or twice to achieve maximum effective dose quickly
Maintenance dose: intermittent doses given to maintain plasma levels.
Ex: Advicor ( niacin + statin drugs) improves lipid lowering action.
Ex: amoxicillen + probenecid (anti-gout) prolongs serum levels of the antibiotic
Ex: Genetic G6PD enzyme deficiency (prevents RBC hemolysis) idiosyncratic reactions to ASA, sulfonamides(African American and Kurdish Jewish populations)