Chapter 1 (Pharmacokinetics)

Question 1

Pharmacokinetics

Answer 1

Refers to how medication’s travel through the body. This results in absorption, distribution, metabolism, and excretion.

Question 2

What are the phases of pharmacokinetics?

Answer 2

Oral, sublingual/buccal, Mucous membranes (rectal, vaginal), inhalation via mouth or nose, intradermal, or topical, subcutaneous or intramuscular and intravenous.

Question 3

Absorption

Answer 3

The transmission of meds from the location of origin. The most common routes of administration are enteral (G.I. track) and parenteral (by injection)

Question 4

Oral

Answer 4

Barriers: meds have to pass through a layer of epithelial cells in the G.I. tract.

Absorption pattern: varies greatly due to
- Stability or solubility of medication
- G.I. pH and emptying time
- presence of food and stomach or the intestines.
- Other medication interactions.
- forms of medication (enteric coated pills or sustained release liquids)

Question 5

Sublingual or Buccal

Answer 5

Barriers: swallowing before dissolution allows for gastric PH to inactivate meds.

Absorption pattern: quick! It goes through highly vascular mucous membranes.

Question 6

Mucus membranes (rectal or vaginal)

Answer 6

Barriers: presence of stool in the rectum or infectious material in the vagina, limits tissue contact.

Absorption pattern: easy absorption with local and systemic effects.

Question 7

Inhalation via mouth or nose

Answer 7

Barriers: inspiratory effort.

Absorption pattern: rapid absorption through alveolar capillary networks.

Question 8

Intradermal or topical

Answer 8

Barriers: proximity of epidermal cells, so they could get in the way.

Absorption pattern: slow, gradual absorption.

This primarily affects local areas, but it can affect systemic areas as well, especially with lipid soluble medication’s.

Question 9

Subcutaneous or intramuscular

Answer 9

Barriers: capillary walls have large spaces between cells, so, no significant barrier!

Absorption pattern:
high solubility = rapid absorption. Low solubility = slow absorption.
High blood perfusion = rapid. Low blood perfusion = slow.

Question 10

Intravenous (IV)

Answer 10

Barriers: NONE
Absorption pattern: immediate and complete.

Question 11

Metabolism

Answer 11

Also known as bio transformation, changes meds into less active or inactive forms by the action of enzymes. This occurs primarily in the liver.

Question 12

Excretion

Answer 12

Elimination of meds from the body, primarily through the kidneys. If you have a kidney dysfunction, this can lead to an increase of duration and intensity of a med response so make sure you monitor the BUN and creatinine.

Question 13

Therapeutic index (TI)

Answer 13

Meds with a high therapeutic index, have a wide safety margin! (No need for routine blood medication level monitoring)

Meds with a low therapeutic index, have a narrow safety margin! (Requires close monitoring of blood levels)

Peak level – highest plasma level.
Trough level – lowest plasma level. (obtain blood level immediately before next dose)
It is important for the nurse to monitor the root of administration of the medication because different routes have different peak levels.
Ex: oral medication can peak one to three hours after admin, however IV medication can peak in 10 minutes!

Question 14

Half-life

Answer 14

Refers to the time it takes a medication in the body to drop by 50%.

Short half-life – meds leave the body quickly! (4 to 8 hours)

Long Half-life – meds, leave the body slowly! (Over more than 24 hours) higher risk for med accumulation and toxicity. Meds can be given at longer intervals without loss of therapeutic effects.

Question 15

Pharmacodynamics

Answer 15

Describes the interactions between medication and target cells, body systems, and organs to produce effects.

Question 16

Agonist

Answer 16

Medications that bind to or mimic the receptor activity that endogenous compounds regulate.

An example would be morphine, it’s an agonist because it activates receptors that produce analgesia.

Question 17

Antagonist

Answer 17

Meds that block the usual receptor activity.

An example would be losartan, it works by blocking angiotensin II receptors on blood vessels, which prevents vasoconstriction.

Question 18

Partial agonist

Answer 18

Acts as both agonist and antagonist.

Question 19

What are the advantages and disadvantages of oral or enteral routes of administration?

Answer 19

Advantages: safe, inexpensive, easy and convenient.
Disadvantages: highly variable absorption, and activation can occur at G.I. tract or first pass effect, and clients must be conscious and cooperative.

Question 20

What are the advantages and disadvantages of subcutaneous injections and intramuscular injections?

Answer 20

Advantages: use for poorly soluble meds, meds that have slow absorption rate.
Disadvantages: more expensive, and convenient, pain with risk of local tissue and nerve damage, and risk of infection at injection site.

Question 21

What are the advantages and disadvantages of an IV?

Answer 21

Advantages: immediate response, control over precise amount of medication, administration for large amount of fluid, and dilutes, irritating medication in free flowing IV fluid.
Disadvantages: expensive, inconvenient, irreversible, high risk for embolism or infection, low circulation can inhibit medicine distribution.

Question 22

What influences medication metabolism?

Answer 22

Age (order adult require smaller doses due to possibility of medicine accumulation), increase in some medication, metabolizing enzymes, first pass effect (liver and activate some meds on first time through, thus requiring an NONENTERAL route (sublingual or IV), similar metabolic, pathways, and nutritional status.

Question 23

What are the outcomes of metabolism?

Answer 23

– Increased renal, excretion of medication’s
– Inactivation of medications.
– increase therapeutic effect next line – activation of pro drugs into active forms.
– Decrease toxicity when active forms become inactive.
– Increase toxicity when inactive forms become active.

Question 24

Medication responses

Answer 24

Attempts to regulate medication responses to maintain plasma levels between minimum effective concentration and toxic concentration.

MEC (minimum effective concentration)

Plasma med level is in therapeutic range when it is affective and not toxic.

Question 25

Distribution

Answer 25

The transportation of medication to sites of action by bodily fluids.

Factors that influence distribution:
– circulation.
-Permeability of cell membrane
– Plasma protein binding

If there are two meds trying to bind to the same site that is called toxicity!