Pharmacokinetics Flashcards
define pharmacokinetics
the study of drug movement throughout the body
3 ways for drugs to cross cell membranes
channels/pores-only the smallest compounds pass through, very little drugs
transport systems- carriers that move drugs from side to side of cell membranes, selective.
direct penetration- most common
TCD
what is P-glycoprotein’s role in transporting drugs across the cell membrane?
P-glycoprotein are a transmembrane proteins that transports a wide variety of drugs out cells
Commonly used RoAdmins=IV
Intravenous
Barriers to absorption: none
Absorption pattern: instantaneous and complete
Advantages: rapid onset, control, large volumes
Disadvantages= can give too fast, risk for infection, skin irritation,
Commonly used RoAdmins=IM
Intramuscular
Barriers to absorption: CAPILLARY WALL
Absorption pattern: rapid or slow depending on solubility
Advantages: Poorly soluble drugs can get into bloodstream faster
Disadvantages: discomfort/inconvenience
Commonly used RoAdmins=subq
no significant barriers to absorption
commonly used RoAdmins=oral
Barriers to absorption: epithelial cells and capillary walls
Absorption pattern: multiple factors affect rate and extent of absorption
Drug movement after absorption: depends on hepatic metabolism
Advantages: safer than injection, easy/convenient
Disadvantages: variability of absorption, inactivation, patient must be alert
what is the first pass effect
The first pass effect is a phenomenon in which a drug gets metabolized at a specific location in the body that results in a reduced concentration of the active drug upon reaching its site of action or the systemic circulation.
Doesn’t always have to be the liver
what factors affect drug distribution
Drug distribution is impacted by several factors related to the drug and the body. The drug-related factors include blood and tissue binding proteins, pH, and perfusion. The body-related factors include body water composition, fat composition, diseases (e.g., volume depletion, burns, third spacing).
Analyze how drugs are metabolized by the cytochrome P450 system.
P450 inducers-increase rate of drug metabolism so plasma levels fall. Because of the levels falling, you may need more of the drug. You also need to be careful about other drugs that are interacting, as they could decrease faster in the body.
how are drugs excreted
Glomerular filtration is the process by which the kidneys filter the blood, removing excess wastes and fluids.
Tubular REABSORPTION is the process that moves solutes and water out of the filtrate and back into your bloodstream.
Active tubular secretion
Tubular secretion gets rid of ions (excess potassium ions and hydrogen ions) and metabolic wastes (such as nitrogenous wastes) to contribute to the maintenance of the normal pH of the blood.
minimum effective concentration
the minimum amount of the drug that can cause a therapeutic effect.
toxic concentration
the concentration where the drug becomes toxic to the patient.
therapeutic range
The therapeutic range of a drug is the dosage range or blood plasma or serum concentration usually expected to achieve the desired therapeutic effect.
Ex: the drug’s therapeutic range is 2.5 to 5 mg
drug half life
the time it takes to clear one half of the total body load of the drug, or for the concentration to drop by 1/2
