Pharmacokinetics Flashcards
What is pharmacokinetics?
Pharmacokinetics is the study of how drugs are impacted by the body
What is absorption?
The movement of a drug from it’s site of administration into the blood
What affects absorption?
The rate of dissolution, blood flow, surface area, lipid solubility, and pH partitioning
How does lipid solubility affect absorption?
An increased lipid solubility allows for the drug to cross the cell membrane easier, thus increasing its rate of absorption
What is rate of absorption?
The rate is how fast the med is absorbed and how quickly effects occur
How does pH partitioning affect absorption?
Drugs favor a pH where they ionize (acid->base, base->acid), thus a pH will be more readily absorbed where their pH favors ionization
What is distribution?
Distribution is the drugs movement from the blood to the interstitial space and into the cells (sites of action)
What affects distribution?
Distribution is affected by blood flow and the drugs ability to exit the vasculature
What affects the ability to exit the vasculature?
Lipid solubility: ability to pass through the cells membranes
Protein binding: binding to albumin and ifs affinity to the bond can prevent the drug from unbinding and getting to the site of action
What is metabolism?
The chemical alteration of the drug structure to promote the degradation and eventual excretion
Where does the majority of metabolism occur in the body?
The liver
What enzymatic pathway promotes drug metabolism
The P450 system
What is a prodrug?
A drug that needs to be metabolized and converted to it’s active form my the liver before it is effective
What effects can metabolism have on toxicitiy?
Through metabolism, the liver can inactivate the drug and prevent toxicity OR it can inactivate the drug and cause it to be converted into a toxic chemical in the body
What is a special consideration for metabolism with infants?
Infants have an underdeveloped liver and require lower doses due to their inability to breakdown medications
What is a special consideration for metabolism with the elderly?
The elderly have a slower metabolic rate and will also need smaller doses due to the prolongation of the drug in their system
What is the first-pass effect?
First-pass effect is when a drug undergoes rapid hepatic inactivation during the first pass through the liver. It can render drugs inactive and ineffective prior to getting to the site of action. This is accounted for in dosing of medications from FDA approval and research.
How does nutrition affect metabolism?
Malnutrition can cause alterations in cofactors of metabolism
What is excretion?
Excretion is the body’s elimination process of the drug
Where are the 2 primary sites for excretion?
The kidneys through the urine and the GI tract through bile and feces
What is a concern with excretion of a drug through the bile?
Enterohepatic recirculation where the medication can be reabsorbed through the GI tract and undergo metabolism again, can increase levels in the body and promote toxicity
What is passive reabsorption?
Drugs travel from the urine back into the blood stream due to lipid solubility or pH ionization
