Pharmacokinetics and Routes of Administration Flashcards
(76 cards)
1
Q
Absorption
A
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
2
Q
Rate of Medication Absorption
A
determines how soon the medication will take effect
3
Q
Amount of Medication
A
determines the intensity of its effect
4
Q
Route of Administration.
A
affects the rate and amount of absorption
5
Q
Oral Route: Barriers to absorption
A
medications must pass through the later of epithelial cells that line the GI tract
6
Q
Oral Route: Absorption Pattern
A
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)
7
Q
Sublingual Route: Barriers to Absorption
A
swallowing before dissolution allows gastric pH to inactivate the mediation.
8
Q
Sublingual Route: Absorption Patterns
A
quick absorption systemically though highly vascular mucous membranes
9
Q
Other Mucous Membranes (rectal, vaginal): Barriers to Absorption
A
Presence of stool in the rectum or infectious material in the vagina limits tissue contact
10
Q
Other Mucous Membranes (rectal, vaginal): Absorption Patterns
A
easy absorption with both local and systemic effects.
11
Q
Inhalation via mouth and nose: barriers to absorption
A
inspiratory effort
12
Q
Inhalation via Mouth and Nose: Absorption Patterns
A
Rapid absorption through alveolar capillary networks
13
Q
Intradermal, Topical: Barriers to Absorption
A
Close proximity to epidermal cells.
14
Q
Intradermal, Topical: Absorption patterns
A
- slow, gradual absorption
- effects primarily local, but systemic as well, especially with lipid-solvable mediations passing through subcutaneous fatty tissue.
15
Q
Subcutaneous, Intramuscular: Barriers to Absorption
A
Capillary walls have large spaces between cels. Therefore, there is no significant barrier.
16
Q
Subcutaneous, Intramuscular: Absorption Patterns
A
- 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
17
Q
Intravenous: Barriers to Absorption
A
no barriers
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Q
Intravenous: Absorption Patterns
A
Immediate: enters directly into the blood
Complete: reached the blood in its entirety
19
Q
Distribution
A
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
20
Q
Circulation
A
conditions that inhibit blood flow or perfusion, such as peripheral vascular or cardiac disease, can delay medication distribution
21
Q
Permeability of the Cell Membrane
A
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
22
Q
Plasma Protein Binding
A
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.
23
Q
Metabolism
A
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.
24
Q
Factors that influence metabolism
A
age increase in some medication-metabolizing enzymes first-pass effect similar metabolic pathways nutritional status
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Age (metabolism)
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.
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Increase in some Medication Metabolizing Enzymes (metabolism)
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
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First- Pass Effect ( Metabolism)
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
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Similar metabolic Pathway (metabolism)
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
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Outcomes of Metabolism
- 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
30
Excretion
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.
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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. RNs use therapeutic levels of many medications to monitor clients responses.
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Therapeutic Index
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.
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Half Life
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)
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Short Half Life
- medication leaves the body quickly (4-8 hr)
| - short-dosing interval or MEC drops between doses.
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Long Half Life
- 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
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Pharmacodynamics
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.
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Agonists
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)
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Antagonists
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.
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Partial Agonist
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.
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Oral or Enteral
Tablets, capsules, liquids, suspensions, elixirs, lozenges
MOST COMMON ROUTE
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Oral Route Contraindication
voting, decreased GI motility, absence of a gag reflex, difficulty swallowing, and a decreased level of consciousness
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RN Considerations with Oral Route
- 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
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Advantages to Oral Route
safe
inexpensive
easy and convenient
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Disadvantages to Oral Route
- 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
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Sublingual
under the tongue
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Buccal
between the cheek and gum
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Sublingual and Buccal
directly enters the bloodstream and bypasses the liver
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Sublingual and Buccal: RN Actions
- 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
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Liquids, Suspensions, and Elixirs: RN Actions
- 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.
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Transdermal
Medication in a skil patch for absorption through the skin, producing systemic effects.
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Transdermal: RN Action
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
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Topical
Painless
| Limited Adverse Effects
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Topical: RN Actions
- apply with a glove, tongue blade, or cotton tipped applicator
- do not apply with bare hand
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Instillation (Drops, Ointments, Sprays)
generally used for eyes, ears, and nose
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Instillation (Eyes)
- 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.
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Instillation (Ears)
- 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.
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Instillation (Nose)
- 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.
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Inhalation
administer through metered dose inhaler (MDI) or dry-powder inhalers (DPI)
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Inhalation (MDI)
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
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Inhalation (DPI)
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.
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Nasogastric and Gastrostomy Tubes: RN Actions
- 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
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Nasogastric and Gastrostomy Tubes: General Guidelines
- 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.
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Suppositories: RN Actions
- follow the manufacturer's directions for storage.
- wear gloves for the procedure
- remove the wrapper, and lubricate the suppository if necessary
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Rectal Suppositories
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.
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Vaginal Suppositories
- 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)
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Parenteral
- 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
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Intradermal
- 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
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Subcutaneous
- 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
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Intramuscular
- 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.
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Advantages of Intramuscular
- use for poorly soluble medication
| - use for administering medication that have slow absorption for an extended period of time. (depot preparations)
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Disadvantages of Intramuscular
- 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
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Z-Track
- 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.
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Intravenous (IV)
- 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.
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Advantages of IV
- 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
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Disadvantages to IV
- 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.
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Epidural
- 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
