ATI Chapter 1: Pharmacokinetics & Routes
Administration & Pharmacody namics (Pt. 1)
1.Pharmacokinetics: refers to how medications travel through the body.
-How the BODY acts on the DRUG
2.Pharmacokinetics in Clinical Practice: i. onset of drug action (how long it will take to see beginning of therapeutic effects) ii.
drug half-life
iii. timing of the peak effect (how long it will take to see the maximum effect of the drug)
iv. duration of drug effects (how long the pt will experience the drugs effect)
v. metabolism (biotransformation) of the drug
vi. site of excretion
3.Critical Concentration: Critical Concentration: the amount of a drug needed to cause a therapeutic effect.
-after a drug is administered, its molecules first must be absorbed into the body, then make their way to *reactive tissues.* If a
drug is going to work properly on these reactive tissues, and thereby produce therapeutic effects, it must attain a *sufficiently
high concentration in the body.*
4.Loading Dose: Loading Dose: a higher dose than that usually used for treatment to reach the critical concentration.
-the critical concentration is then maintained by using the *recommended dosing schedule*
Some drugs may take a prolonged period to reach a critical concentration. If their effects are needed *QUICKLY,* a loading dose is
recommended.
Examples:
1.Digoxin (Lanoxin): drug used to increase the strength of heart contractions
2.Many of the Xanthine Bronchodilators (e.g. aminophylline/theophylline) used to treat asthma attacks are often started by a
loading dose.
5. Dynamic Equilibrium: The *actual concentration that a drug reaches in the body* results from dynamic equilibrium involving
several processes/phases:
,i. Absorption from site of entry ii.
Distribution to the active site
iii. Metabolism (biotransformation) in the LIVER iv.
Excretion from the body
These processes are key elements in determining the *amount of drug (dose)* and the *frequency of dose repetition
(scheduling)* required to achieve the *critical concentration for the desired length of time.*
6. Phase: Absorption (ATI): The transmission of medication from the location of administration [GI tract, muscle, skin, mucous
membrane, or subcutaneous tissue] to the bloodstream.
i. The *RATE* of medication absorption determines how soon the medication will take effect ii. The
*AMOUNT* of medication the body absorbs determines the intensity of its effects
iii. The *ROUTE* of administration affects the rate and amount of absorption
7. Phase: Absorption (textbook): To reach reactive tissues, a drug must first make its way into the *circulating fluids* of the
body.
*Absorption* refers to what happens to a drug from the time it is *introduced to the body until it reaches the circulating fluids
and tissues*
8. Absorption Process: Passive Diffusion, Active Diffusion & Filtration: *Passive Diffusion:* (the major process; does NOT
require cellular energy) Occurs across a *concentration gradient.*
-when there is a greater concentration of a drug on one side of a membrane the drug will move *through the membrane to the
area of LOWER concentration*
i. occurs more quickly if drug molecules are *small, soluble in water AND lipids [cell membranes are made of lipids and proteins],
and has NO electrical charge* that could repel it from the cell membrane
*Active Transport:*
Uses ENERGY to actively move a molecule across a cell membrane.
-the molecule may be *large,* or it may be *moving against the concentration gradient*
i. this process is not very important for absorption of most drugs, BUT it is *very important process in drug excretion through the
kidneys!*
*Filtration:* involves movement through *pores in cell membranes*
-Moves either DOWN a concentration gradient OR as a result of the *pull of plasma proteins* (when pushed by
hydrostatic/blood/or osmotic pressure).
, i. more common process in *drug excretion*
9. Routes & Absorption: The most common routes of administration are *enteral* (through the GI tract and intestinal mucosa) and
*parenteral* (by injection [IM, subQ] or IV). Each route has a unique pattern of absorption. i. Oral
ii.Sublingual, Buccal
iii. Other Mucous Membranes (Rectal, Vaginal) iv. Inhalation via Mouth, Nose v.
Intradermal, Topical vi. Subcutaneous, Intramuscular vii. Intravenous
10. *Fluid Compartments: 1. Intracellular Fluid (ICF): the fluid within cells [cytosol]
2. Extracellular Fluid (ECF): the fluid outside of cells
TWO Major Types of ECF:
i. Interstitial Fluid (ISF): the fluid surrounding the cells ii. Plasma: the fluid component of blood
11. Routes of Administration: Oral: Most frequently used in clinical practice.
*Factors Affecting Oral Absorption:* Medications must pass through the layer of epithelial cells that line the GI tract.
*Absorption Pattern:* varies greatly due to... i.
Stability and Solubility of the med ii. GI pH and
emptying time
iii. Presence of food in the stomach or intestines iv.
Other concurrent meds
v. Forms of med (enteric-coated, liquids)
*BARRIERS (textbook)* aimed at destroying ingested foreign chemicals.
i. *Acidity of Stomach:* the acid breaks down many compounds and *inactivates* others
-The normal volume of the stomach fluid is 20 to 100 mL and the pH is acidic (1.5 to 3.5)
ii. *Length of Time in Stomach:*
-When food is present, stomach acidity is HIGHER and the stomach empties more SLOWLY, thus exposing the drug to the
stomach's acidic environment longer
iii. *Presence of Interacting Foods or Drugs:*
-Foods that INCREASE stomach acidity (milk products/alcohol/protein) also *speed the breakdown of many drugs* -Other
foods may *chemically bind drugs* or *block* their absorption iv. Blood Flow to GI Tract (perfusion to area)
Administration & Pharmacody namics (Pt. 1)
1.Pharmacokinetics: refers to how medications travel through the body.
-How the BODY acts on the DRUG
2.Pharmacokinetics in Clinical Practice: i. onset of drug action (how long it will take to see beginning of therapeutic effects) ii.
drug half-life
iii. timing of the peak effect (how long it will take to see the maximum effect of the drug)
iv. duration of drug effects (how long the pt will experience the drugs effect)
v. metabolism (biotransformation) of the drug
vi. site of excretion
3.Critical Concentration: Critical Concentration: the amount of a drug needed to cause a therapeutic effect.
-after a drug is administered, its molecules first must be absorbed into the body, then make their way to *reactive tissues.* If a
drug is going to work properly on these reactive tissues, and thereby produce therapeutic effects, it must attain a *sufficiently
high concentration in the body.*
4.Loading Dose: Loading Dose: a higher dose than that usually used for treatment to reach the critical concentration.
-the critical concentration is then maintained by using the *recommended dosing schedule*
Some drugs may take a prolonged period to reach a critical concentration. If their effects are needed *QUICKLY,* a loading dose is
recommended.
Examples:
1.Digoxin (Lanoxin): drug used to increase the strength of heart contractions
2.Many of the Xanthine Bronchodilators (e.g. aminophylline/theophylline) used to treat asthma attacks are often started by a
loading dose.
5. Dynamic Equilibrium: The *actual concentration that a drug reaches in the body* results from dynamic equilibrium involving
several processes/phases:
,i. Absorption from site of entry ii.
Distribution to the active site
iii. Metabolism (biotransformation) in the LIVER iv.
Excretion from the body
These processes are key elements in determining the *amount of drug (dose)* and the *frequency of dose repetition
(scheduling)* required to achieve the *critical concentration for the desired length of time.*
6. Phase: Absorption (ATI): The transmission of medication from the location of administration [GI tract, muscle, skin, mucous
membrane, or subcutaneous tissue] to the bloodstream.
i. The *RATE* of medication absorption determines how soon the medication will take effect ii. The
*AMOUNT* of medication the body absorbs determines the intensity of its effects
iii. The *ROUTE* of administration affects the rate and amount of absorption
7. Phase: Absorption (textbook): To reach reactive tissues, a drug must first make its way into the *circulating fluids* of the
body.
*Absorption* refers to what happens to a drug from the time it is *introduced to the body until it reaches the circulating fluids
and tissues*
8. Absorption Process: Passive Diffusion, Active Diffusion & Filtration: *Passive Diffusion:* (the major process; does NOT
require cellular energy) Occurs across a *concentration gradient.*
-when there is a greater concentration of a drug on one side of a membrane the drug will move *through the membrane to the
area of LOWER concentration*
i. occurs more quickly if drug molecules are *small, soluble in water AND lipids [cell membranes are made of lipids and proteins],
and has NO electrical charge* that could repel it from the cell membrane
*Active Transport:*
Uses ENERGY to actively move a molecule across a cell membrane.
-the molecule may be *large,* or it may be *moving against the concentration gradient*
i. this process is not very important for absorption of most drugs, BUT it is *very important process in drug excretion through the
kidneys!*
*Filtration:* involves movement through *pores in cell membranes*
-Moves either DOWN a concentration gradient OR as a result of the *pull of plasma proteins* (when pushed by
hydrostatic/blood/or osmotic pressure).
, i. more common process in *drug excretion*
9. Routes & Absorption: The most common routes of administration are *enteral* (through the GI tract and intestinal mucosa) and
*parenteral* (by injection [IM, subQ] or IV). Each route has a unique pattern of absorption. i. Oral
ii.Sublingual, Buccal
iii. Other Mucous Membranes (Rectal, Vaginal) iv. Inhalation via Mouth, Nose v.
Intradermal, Topical vi. Subcutaneous, Intramuscular vii. Intravenous
10. *Fluid Compartments: 1. Intracellular Fluid (ICF): the fluid within cells [cytosol]
2. Extracellular Fluid (ECF): the fluid outside of cells
TWO Major Types of ECF:
i. Interstitial Fluid (ISF): the fluid surrounding the cells ii. Plasma: the fluid component of blood
11. Routes of Administration: Oral: Most frequently used in clinical practice.
*Factors Affecting Oral Absorption:* Medications must pass through the layer of epithelial cells that line the GI tract.
*Absorption Pattern:* varies greatly due to... i.
Stability and Solubility of the med ii. GI pH and
emptying time
iii. Presence of food in the stomach or intestines iv.
Other concurrent meds
v. Forms of med (enteric-coated, liquids)
*BARRIERS (textbook)* aimed at destroying ingested foreign chemicals.
i. *Acidity of Stomach:* the acid breaks down many compounds and *inactivates* others
-The normal volume of the stomach fluid is 20 to 100 mL and the pH is acidic (1.5 to 3.5)
ii. *Length of Time in Stomach:*
-When food is present, stomach acidity is HIGHER and the stomach empties more SLOWLY, thus exposing the drug to the
stomach's acidic environment longer
iii. *Presence of Interacting Foods or Drugs:*
-Foods that INCREASE stomach acidity (milk products/alcohol/protein) also *speed the breakdown of many drugs* -Other
foods may *chemically bind drugs* or *block* their absorption iv. Blood Flow to GI Tract (perfusion to area)
