WEEK 5 N100 GUIDED NOTES
MEDICATION ADMINISTRATION
1. Medication route and Pharmacokinetics
Pharmacokinetics refers to how medications ______Travel_ through the body.
Medications undergo a variety of biochemical processes that result in absorption, distribution,
metabolism, and excretion.
Phases of pharmacokinetics
Absorption The transmission of medications from the location of administration (gastrointestinal
[GI] tract, muscle, skin, or subcutaneous tissue) to the ______bloodstream_____________.
The most common routes of administration are enteral (through the GI tract) and parenteral (by
injection).
Each of these routes has a unique pattern of absorption.
The rate of medication absorption determines how soon the medication takes effect.
The amount of medication the body absorbs determines its intensity.
The route of administration affects the rate and amount of absorption.
2. Route: Oral
Barriers to absorption:
Medications must pass through the layer of epithelial cells that line the GI tract.
Absorption pattern
varies greatly due to
Stability and solubility of the medication
Gastrointestinal pH and emptying time
Presence of food in the stomach or intestines
Concurrent medications
Forms of medications (enteric-coated pills, liquids) Route:
Subcutaneous and intramuscular
Barriers to absorption: The capillary walls have large spaces between cells. Therefore, there is no
significant barrier.
Absorption pattern: factors determining the rate of absorption
Solubility of the medication in water
Highly soluble medications have rapid absorption (10 to 30 min).
Poorly soluble medications have slow absorption.
Blood perfusion at the site of injection
Sites with high blood perfusion have rapid absorption.
Sites with low blood perfusion have slow absorption.
Route: Intravenous
Barriers to absorption: No barriers
Absorption pattern
Immediate: enters directly into the blood
Complete: reaches the blood in its entirety
Distribution The transportation of medications to sites of action by bodily fluids.
Factors influencing distribution
Circulation: Conditions that inhibit blood flow or perfusion (peripheral vascular or cardiac disease)
can delay medication distribution.
Permeability of the cell membrane: The medication must be able to pass through tissues and
membranes to reach its target area. Medications that are lipid-soluble or have a transport system can
cross the blood-brain barrier and the placenta.
, WEEK 5 N100 GUIDED NOTES
Plasma protein binding: Medications compete for protein binding sites within the bloodstream,
primarily albumin.
The ability of a medication to bind to a protein can affect how much of the medication will leave
and travel to target tissues.
Two medications can compete for the same binding sites, resulting in toxicity.
Metabolism (biotransformation) Changes medications into less active forms or inactive forms by
the action of enzymes.
This occurs primarily in the liver, but also takes place in the kidneys, lungs, intestines, and blood.
3. Factors influencing medication metabolism rate
Age: Infants have a limited medication-metabolizing capacity.
The aging process also can influence medication metabolism but varies with the individual.
In general, hepatic medication metabolism tends to decline with age. Older adults require smaller
doses of medications due to the possibility of accumulation in the body.
An increase in some medication-metabolizing enzymes: This can metabolize a particular
medication sooner, requiring an increase in dosage of that medication to maintain a therapeutic level.
It can also cause an increase in the metabolism of other concurrent-use medications.
First-pass effect: The liver inactivates some medications on their first pass through the liver. Thus,
they require a nonenteral route (sublingual, IV) because of their high first-pass effect.
Similar metabolic pathways: When the same pathway metabolizes two medications, it can alter the
metabolism of one or both of them. In this way, the rate of metabolism can decrease for one or both
of the medications, leading to medication accumulation.
Nutritional status: Clients who are malnourished can be deficient in the factors that are necessary to
produce specific medication-metabolizing enzymes, thus impairing medication metabolism.
Excretion The elimination of medications from the body, primarily through the
____kidney____________. Elimination also takes place through the liver, lungs, intestines, and
exocrine glands (in breast milk). Kidney ______failure/decreased function____ can lead to an
increase in the duration and intensity of a medication’s response
4. MEDICATION RESPONSES
Medication dosing attempts to regulate medication responses to maintain plasma levels between the
minimum effective concentration (MEC) and the toxic concentration.
A plasma medication level is in the therapeutic range when it is effective and not toxic. Nurses use
therapeutic levels of many medications to monitor clients’ responses.
THERAPEUTIC INDEX (TI) Medications with a high TI have a wide safety margin; therefore,
there is no need for routine blood medication-level monitoring. Medications with a low TI require
close monitoring of medication levels. Nurses should consider the route of administration when
monitoring for peak levels (highest plasma level when elimination = absorption).
For example, an oral medication can peak from 1 to 3 hr after administration.
If the route is IV, the peak time might occur within 10 min.
Refer to a medication reference or a pharmacist for specific medication peak times.
For trough levels, obtain a blood sample immediately before the next medication dose, regardless
of the route of administration.
A plateau is a medication concentration in plasma during a series of doses. HALF-LIFE (t1/2)
The time for the medication in the body to drop by 50%.
Liver and kidney function affect half-life. It usually takes four half-lives to achieve a steady blood
concentration (medication intake = medication metabolism and excretion).
Short half-life: Medications leave the body quickly: 4 to 8 hr.
, WEEK 5 N100 GUIDED NOTES
_______Long______half-life Medications leave the body more slowly: over more than 24 hr,
with a greater risk for medication accumulation and toxicity.
Short-dosing interval or MEC drops between doses. Can give medications at longer intervals
without a loss of therapeutic effects. Medications take a longer time to reach a steady state.
Pharmacodynamics (mechanism of action)
The interactions between medications and target cells, body systems, and organs to produce
effects. These interactions result in functional changes that are the mechanism of action of the
medication.
Agonist: Medication that can mimic the receptor activity that endogenous compounds regulate.
For example, morphine is an agonist because it activates the receptors that produce analgesia,
sedation, constipation, and other effects. (Receptors are the medication’s target sites on or within
the cells.)
Antagonist: Medication that can block the usual receptor activity that endogenous compounds
regulate or the receptor activity of other medications. For example, losartan, an angiotensin II
receptor blocker, is an antagonist. It works by blocking angiotensin II receptors on blood vessels,
which prevents vasoconstriction.
Partial agonists: Medication that acts as an agonist and an antagonist, with limited affinity to
receptor sites. For example, nalbuphine acts as an antagonist at mu receptors and an agonist at
kappa receptors, causing analgesia at low doses with minimal respiratory depression.
5. Routes of administration
ORAL OR ENTERAL Tablets, capsules, liquids, suspensions, elixirs, lozenges
Most common route
Least expensive
Convenient
NURSING ACTIONS
For liquids, suspension, and elixirs, follow directions for dilution and shaking. To prepare the
medication, place a medicine cup on a flat surface before pouring, and ensure the base of the
meniscus (lowest fluid line) is at the level of the dose.
Contraindications for oral medication administration include vomiting, decreased GI motility,
absence of a gag reflex, difficulty swallowing, and a decreased level of consciousness.
Have clients sit upright at a 90° angle to facilitate swallowing.
Administer irritating medications (analgesics) with small amounts of food.
Do not mix with large amounts of food or beverages in case clients cannot consume the entire
quantity.
Avoid administration with interacting foods or beverages (grapefruit juice).
Administer oral medications as prescribed, and follow directions for whether medication is to be
taken on an empty stomach (30 min to 1 hr before meals, 2 hr after meals) or with food.
Follow the manufacturer’s directions for crushing, cutting, and diluting medications. Break or cut
scored tablets only.
Make sure clients swallow enteric-coated or time-release medications _____whole______.
Use a liquid form of the medication to facilitate swallowing whenever possible
Sublingual and buccal Directly enters the bloodstream and bypasses the liver
Sublingual: under the tongue
Buccal: between the cheek and the gum
CLIENT EDUCATION
Keep the medication in place until complete absorption occurs.
Do not eat or drink while the tablet is in place or until it has completely dissolved.
MEDICATION ADMINISTRATION
1. Medication route and Pharmacokinetics
Pharmacokinetics refers to how medications ______Travel_ through the body.
Medications undergo a variety of biochemical processes that result in absorption, distribution,
metabolism, and excretion.
Phases of pharmacokinetics
Absorption The transmission of medications from the location of administration (gastrointestinal
[GI] tract, muscle, skin, or subcutaneous tissue) to the ______bloodstream_____________.
The most common routes of administration are enteral (through the GI tract) and parenteral (by
injection).
Each of these routes has a unique pattern of absorption.
The rate of medication absorption determines how soon the medication takes effect.
The amount of medication the body absorbs determines its intensity.
The route of administration affects the rate and amount of absorption.
2. Route: Oral
Barriers to absorption:
Medications must pass through the layer of epithelial cells that line the GI tract.
Absorption pattern
varies greatly due to
Stability and solubility of the medication
Gastrointestinal pH and emptying time
Presence of food in the stomach or intestines
Concurrent medications
Forms of medications (enteric-coated pills, liquids) Route:
Subcutaneous and intramuscular
Barriers to absorption: The capillary walls have large spaces between cells. Therefore, there is no
significant barrier.
Absorption pattern: factors determining the rate of absorption
Solubility of the medication in water
Highly soluble medications have rapid absorption (10 to 30 min).
Poorly soluble medications have slow absorption.
Blood perfusion at the site of injection
Sites with high blood perfusion have rapid absorption.
Sites with low blood perfusion have slow absorption.
Route: Intravenous
Barriers to absorption: No barriers
Absorption pattern
Immediate: enters directly into the blood
Complete: reaches the blood in its entirety
Distribution The transportation of medications to sites of action by bodily fluids.
Factors influencing distribution
Circulation: Conditions that inhibit blood flow or perfusion (peripheral vascular or cardiac disease)
can delay medication distribution.
Permeability of the cell membrane: The medication must be able to pass through tissues and
membranes to reach its target area. Medications that are lipid-soluble or have a transport system can
cross the blood-brain barrier and the placenta.
, WEEK 5 N100 GUIDED NOTES
Plasma protein binding: Medications compete for protein binding sites within the bloodstream,
primarily albumin.
The ability of a medication to bind to a protein can affect how much of the medication will leave
and travel to target tissues.
Two medications can compete for the same binding sites, resulting in toxicity.
Metabolism (biotransformation) Changes medications into less active forms or inactive forms by
the action of enzymes.
This occurs primarily in the liver, but also takes place in the kidneys, lungs, intestines, and blood.
3. Factors influencing medication metabolism rate
Age: Infants have a limited medication-metabolizing capacity.
The aging process also can influence medication metabolism but varies with the individual.
In general, hepatic medication metabolism tends to decline with age. Older adults require smaller
doses of medications due to the possibility of accumulation in the body.
An increase in some medication-metabolizing enzymes: This can metabolize a particular
medication sooner, requiring an increase in dosage of that medication to maintain a therapeutic level.
It can also cause an increase in the metabolism of other concurrent-use medications.
First-pass effect: The liver inactivates some medications on their first pass through the liver. Thus,
they require a nonenteral route (sublingual, IV) because of their high first-pass effect.
Similar metabolic pathways: When the same pathway metabolizes two medications, it can alter the
metabolism of one or both of them. In this way, the rate of metabolism can decrease for one or both
of the medications, leading to medication accumulation.
Nutritional status: Clients who are malnourished can be deficient in the factors that are necessary to
produce specific medication-metabolizing enzymes, thus impairing medication metabolism.
Excretion The elimination of medications from the body, primarily through the
____kidney____________. Elimination also takes place through the liver, lungs, intestines, and
exocrine glands (in breast milk). Kidney ______failure/decreased function____ can lead to an
increase in the duration and intensity of a medication’s response
4. MEDICATION RESPONSES
Medication dosing attempts to regulate medication responses to maintain plasma levels between the
minimum effective concentration (MEC) and the toxic concentration.
A plasma medication level is in the therapeutic range when it is effective and not toxic. Nurses use
therapeutic levels of many medications to monitor clients’ responses.
THERAPEUTIC INDEX (TI) Medications with a high TI have a wide safety margin; therefore,
there is no need for routine blood medication-level monitoring. Medications with a low TI require
close monitoring of medication levels. Nurses should consider the route of administration when
monitoring for peak levels (highest plasma level when elimination = absorption).
For example, an oral medication can peak from 1 to 3 hr after administration.
If the route is IV, the peak time might occur within 10 min.
Refer to a medication reference or a pharmacist for specific medication peak times.
For trough levels, obtain a blood sample immediately before the next medication dose, regardless
of the route of administration.
A plateau is a medication concentration in plasma during a series of doses. HALF-LIFE (t1/2)
The time for the medication in the body to drop by 50%.
Liver and kidney function affect half-life. It usually takes four half-lives to achieve a steady blood
concentration (medication intake = medication metabolism and excretion).
Short half-life: Medications leave the body quickly: 4 to 8 hr.
, WEEK 5 N100 GUIDED NOTES
_______Long______half-life Medications leave the body more slowly: over more than 24 hr,
with a greater risk for medication accumulation and toxicity.
Short-dosing interval or MEC drops between doses. Can give medications at longer intervals
without a loss of therapeutic effects. Medications take a longer time to reach a steady state.
Pharmacodynamics (mechanism of action)
The interactions between medications and target cells, body systems, and organs to produce
effects. These interactions result in functional changes that are the mechanism of action of the
medication.
Agonist: Medication that can mimic the receptor activity that endogenous compounds regulate.
For example, morphine is an agonist because it activates the receptors that produce analgesia,
sedation, constipation, and other effects. (Receptors are the medication’s target sites on or within
the cells.)
Antagonist: Medication that can block the usual receptor activity that endogenous compounds
regulate or the receptor activity of other medications. For example, losartan, an angiotensin II
receptor blocker, is an antagonist. It works by blocking angiotensin II receptors on blood vessels,
which prevents vasoconstriction.
Partial agonists: Medication that acts as an agonist and an antagonist, with limited affinity to
receptor sites. For example, nalbuphine acts as an antagonist at mu receptors and an agonist at
kappa receptors, causing analgesia at low doses with minimal respiratory depression.
5. Routes of administration
ORAL OR ENTERAL Tablets, capsules, liquids, suspensions, elixirs, lozenges
Most common route
Least expensive
Convenient
NURSING ACTIONS
For liquids, suspension, and elixirs, follow directions for dilution and shaking. To prepare the
medication, place a medicine cup on a flat surface before pouring, and ensure the base of the
meniscus (lowest fluid line) is at the level of the dose.
Contraindications for oral medication administration include vomiting, decreased GI motility,
absence of a gag reflex, difficulty swallowing, and a decreased level of consciousness.
Have clients sit upright at a 90° angle to facilitate swallowing.
Administer irritating medications (analgesics) with small amounts of food.
Do not mix with large amounts of food or beverages in case clients cannot consume the entire
quantity.
Avoid administration with interacting foods or beverages (grapefruit juice).
Administer oral medications as prescribed, and follow directions for whether medication is to be
taken on an empty stomach (30 min to 1 hr before meals, 2 hr after meals) or with food.
Follow the manufacturer’s directions for crushing, cutting, and diluting medications. Break or cut
scored tablets only.
Make sure clients swallow enteric-coated or time-release medications _____whole______.
Use a liquid form of the medication to facilitate swallowing whenever possible
Sublingual and buccal Directly enters the bloodstream and bypasses the liver
Sublingual: under the tongue
Buccal: between the cheek and the gum
CLIENT EDUCATION
Keep the medication in place until complete absorption occurs.
Do not eat or drink while the tablet is in place or until it has completely dissolved.
