Pharmacokinetics and Routes of Administration

Question 1

Absorption

Answer 1

is the transmission of mediations from the location of administration 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 will take effect.
• the amount of medication the body absorbs determines the intensity of its effects.
• the route of administration affects the rate and the amount of absorption

Question 2

Rate of Medication Absorption

Answer 2

determines how soon the medication will take effect

Question 3

Amount of Medication

Answer 3

determines the intensity of its effect

Question 4

Route of Administration.

Answer 4

affects the rate and amount of absorption

Question 5

Oral Route: Barriers to absorption

Answer 5

medications must pass through the later of epithelial cells that line the GI tract

Question 6

Oral Route: Absorption Pattern

Answer 6

Varies greatly due to:

• stability and solubility of the mediation
• GI pH and emptying time
• presence of food in the stomach and intestines.
• Other concurrent mediations
• Forms of mediations (enteric-coated pills, liquids)

Question 7

Sublingual Route: Barriers to Absorption

Answer 7

swallowing before dissolution allows gastric pH to inactivate the mediation.

Question 8

Sublingual Route: Absorption Patterns

Answer 8

quick absorption systemically though highly vascular mucous membranes

Question 9

Other Mucous Membranes (rectal, vaginal): Barriers to Absorption

Answer 9

Presence of stool in the rectum or infectious material in the vagina limits tissue contact

Question 10

Other Mucous Membranes (rectal, vaginal): Absorption Patterns

Answer 10

easy absorption with both local and systemic effects.

Question 11

Inhalation via mouth and nose: barriers to absorption

Answer 11

inspiratory effort

Question 12

Inhalation via Mouth and Nose: Absorption Patterns

Answer 12

Rapid absorption through alveolar capillary networks

Question 13

Intradermal, Topical: Barriers to Absorption

Answer 13

Close proximity to epidermal cells.

Question 14

Intradermal, Topical: Absorption patterns

Answer 14

• slow, gradual absorption
• effects primarily local, but systemic as well, especially with lipid-solvable mediations passing through subcutaneous fatty tissue.

Question 15

Subcutaneous, Intramuscular: Barriers to Absorption

Answer 15

Capillary walls have large spaces between cels. Therefore, there is no significant barrier.

Question 16

Subcutaneous, Intramuscular: Absorption Patterns

Answer 16

• solubility of the medication in water: Highly soluble medications have rapid absorption (10-30 minutes); 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

Question 17

Intravenous: Barriers to Absorption

Answer 17

no barriers

Question 18

Intravenous: Absorption Patterns

Answer 18

Immediate: enters directly into the blood
Complete: reached the blood in its entirety

Question 19

Distribution

Answer 19

is the transport of medications to sites of action by bodily fluids. Factors influencing distribution: circulation, permeability of the cell membrane, and plasma protein binding

Question 20

Circulation

Answer 20

conditions that inhibit blood flow or perfusion, such as peripheral vascular or cardiac disease, can delay medication distribution

Question 21

Permeability of the Cell Membrane

Answer 21

the medication must be able to pass through tissues and membranes to reach its target area. Mediations that are lipid soluble or have a transport system can cross the blood-brain barrier and the placenta

Question 22

Plasma Protein Binding

Answer 22

Medications compete for protein binding sites within the bloodstream, primarily albumin. The ability of the medication to bind to a protein can affect how much of the medication will leave and travel to target tissues. Two mediation can compete for the same binding sites, resulting in toxicity.

Question 23

Metabolism

Answer 23

Biotransformation
changes medications into less active or inactive forms by the action of enzymes. This occurs primarily in the liver, but it also takes place in the kidneys, lungs, intensities, and blood.

Question 24

Factors that influence metabolism

Answer 24

age
increase in some medication-metabolizing enzymes
first-pass effect
similar metabolic pathways
nutritional status

Question 25

Age (metabolism)

Answer 25

infants have a limited medication-metabolizing capacity. the aging process also can influence mediation 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.

Question 26

Increase in some Medication Metabolizing Enzymes (metabolism)

Answer 26

this can metabolize a particular medication sooner, requiring an increase in dosage of that medication to maintain therapeutic level. It can also cause an increase in metabolism of other concurrent-use medications

Question 27

First- Pass Effect ( Metabolism)

Answer 27

the liver inactivates some medications on their first pas through the liver, and thus require a nonenteral route (sublingual, IV) because of their high first-pass effect

Question 28

Similar metabolic Pathway (metabolism)

Answer 28

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

Question 29

Outcomes of Metabolism

Answer 29

• increased renal excretion of medication
• inactivation of medication
• increased therapeutic effect
• activation of pro-medicavition (also called pro-drugs) into active forms
• decrease toxicity when active forms of medications become inactive forms
• increased toxicity when inactive forms of medications become active forms

Question 30

Excretion

Answer 30

is the elimination of medication from the body, primarily through the kidneys. Elimination also takes place through the liver, lungs, intestines, and exocrine glands (such as incrust milk). Kidney function can lead to an increase in duration and intensity of a medications response, so it is important to monitor BUN and creatinine levels.

Question 31

Medication Responses

Answer 31

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. RNs use therapeutic levels of many medications to monitor clients responses.

Question 32

Therapeutic Index

Answer 32

Medications with a high therapeutic index (TI) have a wide safety margin. Therefore there is no need for routine serum medication-level monitoring Medications with a low TI require close monitoring of serum medication levels. RNs 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 1-3 hours after administration. If the route is IV, the peak time might occur within 10 minutes. For trough levels, obtain a blood sample immediately before the next medication dose, regardless of the route of administration. A plateau is a mediations concentration in the plasma during a serious of doses.

Question 33

Half Life

Answer 33

refers to the time for the medication in the body to drop by 50%. Liver and kidney function affect the half life. It usually takes 4 half lives to achieve a steady state of serum concentration (medication intake = medication metabolism and excretion)

Question 34

Short Half Life

Answer 34

• medication leaves the body quickly (4-8 hr)

- short-dosing interval or MEC drops between doses.

Question 35

Long Half Life

Answer 35

• medications leave the body more slowly: over more than 24 hrL with a greater risk for medication accumulation and toxicity
• can give mediations at longer intervals without loss of therapeutic effects.
• medications take longer time to reach a steady state

Question 36

Pharmacodynamics

Answer 36

describes the interaction between medications and target cells, body systems, and organs to produce effects. These interactions result in functional changes that are the mechanism of actions of the mediation. Medications interact with cell sin one of two ways or in both.

Question 37

Agonists

Answer 37

medications that bind to or 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)

Question 38

Antagonists

Answer 38

medications that can block the usual receptor activity that endogenous compounds regulate or the receptor activity of other medications.

For example: losartan, an angiotensin 2 receptor blocker, is an antagonist. It works by blocking angiotensinogen 2 receptors on blood vessels, which prevents vasoconstriction.

Question 39

Partial Agonist

Answer 39

act as agonists and antagonists, with limited affinity to receptor sites.

For example: nalbuphine acts as an antagonist at mu receptors and an agonist at kappa receptors, causing analgesia with minimal respiratory depression at low doses.

Question 40

Oral or Enteral

Answer 40

Tablets, capsules, liquids, suspensions, elixirs, lozenges

MOST COMMON ROUTE

Question 41

Oral Route Contraindication

Answer 41

voting, decreased GI motility, absence of a gag reflex, difficulty swallowing, and a decreased level of consciousness

Question 42

RN Considerations with Oral Route

Answer 42

• have clients sit upright at a 90 degree angle to facilitate swallowing
• administer irrigating medications, such as analgesics. with a small amount 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, such as grapefruit juice
• in general, administer oral medications on an empty stomach (30 minutes to.1 hour before meals, 2 hours after)
• follow the manufacturers directions for causing, cutting, and diluting medications. Break or cut scored tablets only.
• make sure clients swallow enteric-coated or Tim-release medications whole.
• use liquid form of medication to facilitate swallowing whenever possible

Question 43

Advantages to Oral Route

Answer 43

safe
inexpensive
easy and convenient

Question 44

Disadvantages to Oral Route

Answer 44

• oral medications have highly variable absorption
• inactivation can occur in the GI tract or by first-pass effect
• clients must be cooperative and conscious
• contraindications include nausea and vomiting

Question 45

Sublingual

Answer 45

under the tongue

Question 46

Buccal

Answer 46

between the cheek and gum

Question 47

Sublingual and Buccal

Answer 47

directly enters the bloodstream and bypasses the liver

Question 48

Sublingual and Buccal: RN Actions

Answer 48

• instruct clients to keep the medication in place until complete absorption occurs
• Clients should not eat or drink while the table is in place or until it has completely dissolved

Question 49

Liquids, Suspensions, and Elixirs: RN Actions

Answer 49

• follow directions for dilution and shaking.
• when administering the medication, pour it into a cup on flat surface. Make sure the base of the meniscus (lowest fluid line) is at the level of the dose.

Question 50

Transdermal

Answer 50

Medication in a skil patch for absorption through the skin, producing systemic effects.

Question 51

Transdermal: RN Action

Answer 51

Instruct Clients To:

• apple patches to ensure proper dosing
• wash the skin with soap and water, and dry to thoroughly before applying a new patch.
• place the patch on a hairless area, and rotate sites daily to prevent skin irritation

Question 52

Topical

Answer 52

Painless

Limited Adverse Effects

Question 53

Topical: RN Actions

Answer 53

• apply with a glove, tongue blade, or cotton tipped applicator
• do not apply with bare hand

Question 54

Instillation (Drops, Ointments, Sprays)

Answer 54

generally used for eyes, ears, and nose

Question 55

Instillation (Eyes)

Answer 55

• have client sit upright or lie supine, tilt their head slightly, and look up at the ceiling.
• rest your dominant hand on the clients forehead, hold the dropper above the conjunctival sac about 1-2cm, drop the medication into the center of the sac, avoid placing it directly on the cornea, and have them close their eye gently.
• apply gentle pressure with your finger and clean facial tissue on the nasolacrimal duct for 30-60 seconds to precent systemic absorption of the medication.
• if instilling more than one medication in the same eyes, wait at least 5 minutes between them
• for eye ointment, apply a thin ribbon to the edge of the lower eyelid from the inner to the outer canthus.

Question 56

Instillation (Ears)

Answer 56

• have clients sit upright or lie on their side.
• straighten the ear canal by pulling the auricle upward and outward for adults OR down and back for children. Hold the dropper 1cm above the ear canal, instill the mediation, and then gently apply pressure with your finger to the tragus of the ear unless it is too painful.
• do not press a cotton ball deep into the ear canal. If necessary, gently place it into the outermost part of the ear canal.
• have clients remain in the side lying position if possible for 2-3 minutes after instilling drops.

Question 57

Instillation (Nose)

Answer 57

• use medical aseptic technique when administering medications into the nose.
• have clients lie supine with their head positioned to allow the medication to enter the appropriate nasal passage.
• use your dominant hand to instill the drops, supporting the head with your non dominant hand.
• instruct clients to breathe through the mouth, stay in a supine position, and not blow their nose for 5 minutes after drop instillation.

Question 58

Inhalation

Answer 58

administer through metered dose inhaler (MDI) or dry-powder inhalers (DPI)

Question 59

Inhalation (MDI)

Answer 59

Instruct clients to:

• remove the cap from the inhalers mouth piece
• shake the inhaler vigorously
• hold the inhaler with the mouthpiece at the bottom
• hold the inhaler with your thumb near the mouthpiece and your index or middle fingers at the top
• hold the inhaler about 2-4cm away from the front of your mouth or close your mouth around the mouthpiece of the inhaler with the opening pointing toward the back of your throat
• take a deep breath and then exhale
• tilt your head back slightly, press the inhalers, and, at the same time, begin a slow, deep inhalation breath. Continue to breathe in slowly and deeply for 3 to 5 seconds to facilitate delivery to the air passages.
• hold breath for 10 seconds to allow the medication to deposit in your airways.
• take the inhaler out of your mouth and slowly exhale through pursed lips
• resume normal breathing
• a spacer keeps the medication in the device longer, thereby increasing the amount of medication the device delivers to the lungs and decreasing the amount of mediation in the oropharynx
• for clients who use a spacer:
• remove the covers from the mouthpieces of the inhaler and of the spacer
• insert the MDI into the end of the spacer
• shake the inhaler 5-6 times
• exhale completely and then close your mouth around the spacers mouthpiece. continue as with an MDI

Question 60

Inhalation (DPI)

Answer 60

Instruct Clients to:

• do not shake the device
• take the cover off the mouthpiece
• follow the manufacturers directions for preparing the medication, such as turning the wheel of the inhaler or loading an medication pellet.
• exhale completely
• place the mouthpiece between your lips and take a deep inhalation breath through your mouth.
• hold your breath for 5-10 seconds.
• take the inhaler out of your mouth and slowly exhale through pursed lips
• resume normal breathing
• clients who need more than one puff should weight the length of time the provider specifies before self-administering the second puff
• instruct clients to rinse their mouth out with water or brush their teeth if using a corticosteroid inhaler to reduce the risk of fungal infections of the mouth.
• instruct the clients to remove the canister and rinse the inhaler, cap, and spacer once a day with warm water and dry them completely before using the inhaler again.

Question 61

Nasogastric and Gastrostomy Tubes: RN Actions

Answer 61

• verify proper tube placement
• use a syringe and allow the medication to flow in by gravity or push it in with the plunger of the syringe
• to precent clogging, flush the tubing before and after each medication with 15-30mL of warm sterile water/
• Flush with another 15-30mL of warm sterile water after instilling all the medications

Question 62

Nasogastric and Gastrostomy Tubes: General Guidelines

Answer 62

• use liquid forms of mediations; if no available, consider causing medications if appropriate guidelines allow.
• do no administer sublingual medications through the NG tube (may give sublingual medications under the tongue)
• do not crush specifically prepared oral medications (extended/time-release, fluid filled, enteric-coated)
• administer each medication separately
• do not mix medications with enteral feedings.
• completely dissolve crushed tablets and capsule contents in 15-30mL of sterile water prior to administration.

Question 63

Suppositories: RN Actions

Answer 63

• follow the manufacturer’s directions for storage.
• wear gloves for the procedure
• remove the wrapper, and lubricate the suppository if necessary

Question 64

Rectal Suppositories

Answer 64

Thin, buller-shapped medications

• position clients in the LLR or Sims position
• insert the suppository just beyond the internal sphincter
• Instruct clients to remain flat or in the LLR position for at least 5 minutes after insertion to retain the suppository. Absorption times may vary with this medication.

Question 65

Vaginal Suppositories

Answer 65

• position clients supine with their knees bet and their feet flat on the bed and close to their hips (modifies lithotomy or dorsal recumbent position)
• use the applicator if available
• insert the suppository along the posterior wall of the vagina 7.5-10cm
• instruct clients to remain supine for at least 5 minutes after insertion to retain the suppository
• if using an applicator, wash it with soap and water (if it is disposable, discard it)

Question 66

Parenteral

Answer 66

• the vestus lateralis is best for infants 1 year and younger
• the ventrogluteal site is preferable for IM injections and for injecting volumes exceeding 2mL
• the deltoid site has a smaller muscle mass and can only accommodate up to 1mL of fluids
• use a needle size and length appropriate for the type of injection and the clients size. Syringe size should approximate the volume of medication
• use a tuberculin syringe for solution volumes less the 0.5mL
• rotate injection sites to enhance medication absorption, and document each site.
• do not use injection sites that are edematous, inflamed, or have moles, birthmarks, or scars
• for IV administration, immediately monitor clients for therapeutic and adverse effects
• discard all sharps (broken ampule bottles, needles) in leak- and puncture- proof containers

Question 67

Intradermal

Answer 67

• use for tuberculin testing or checking for medication or allergy sensitivities
• use small amount of solution (0.01-0.1mL) in a tuberculin syringe with a fine-gauge needle (26-27 gauge) in lightly pigmented, thin-skinned, hairless sites (the inner surface of the mid-forearm or scapular area of the back) at a 1-15 degree angle.
• insert needle with the bevel up. A small bleb should appear.
• do not massage the site after injection

Question 68

Subcutaneous

Answer 68

• use for small doses of nonirritating, water-soluble medications, such as insulin and heparin
• use a 3/8-5/8-inch, 27-27G needle or a 28-31G insulin syringe. Inject no more than 1.5mL of solution
• select sires that have adequate fat-pad size (abdomen, upper hips, lateral upper arms, thighs)
• for average sized clients, pinch up the skin and inject at 45-90 degree angle. For clients who are obese, use a 90 degree angle

Question 69

Intramuscular

Answer 69

• use for irritating medications, solutions in oils, and aqueous suspensions
• the most common sites are ventrogluteal, dorsogluteal, deltoid, and vastus lateralis (pediatrics)
• use needle size 18-27G (usually 22-25G), 1-1.5” long, and inject at an angle of 90 degree angle. Solution volume is usually 1-3mL. Divide larger volumes into two syringes and use two different sites.

Question 70

Advantages of Intramuscular

Answer 70

• use for poorly soluble medication

- use for administering medication that have slow absorption for an extended period of time. (depot preparations)

Question 71

Disadvantages of Intramuscular

Answer 71

• IM injections are more costly
• IM injection are inconvenient
• there can be pain with the risk for local tissue damage and nerve damage
• there is a risk of infection at the injection site

Question 72

Z-Track

Answer 72

• use the technique for all IM injections because it is less painful and it prevents medication from leaking back into the subcutaneous tissue.
• use for medication that cause visible or permanent skin stains, such as iron preparations.

Question 73

Intravenous (IV)

Answer 73

• use for administering medications, fluid, and blood products
• vascular access devices can be for short-term use (catheters) or long term use (infusion ports). Use 16G devices for clients who have trauma, 18G during surgery and for blood administration, and 22-24G for children, older adults, or clients who have medical issues or are stale postoperatively.
• peripheral veins in the arms or hands are preferable. Ask clients which site they prefer. For newborns, use veins in the hands, lower legs, and feet. After administration, immediately monitor for therapeutic and adverse effects.

Question 74

Advantages of IV

Answer 74

• onset is rapid, and absorption into the blood is immediate, which provides an immediate response.
• the route allows control over the precise amount of medication to administer
• it allows for administration of large volumes of fluid
• it dilutes irritating medication in a free-flowing IV fluid

Question 75

Disadvantages to IV

Answer 75

• IV injections are even more costly
• IV injections are inconvenient
• absorption of medication into the blood is immediate. This is potentially dangerous if giving the wrong dosage or the wrong medication.
• there is an increased risk for infection or embolism with IV injections
• poor circulation can inhibit the medications distribution.

Question 76

Epidural

Answer 76

• use for IV opioid analgesia (morphine and fentanyl)
• the clinician advances the catheter through the needle into the epidural space at the level of the 4th or 5th vertebra
• use an infusion pump to administer medication