Pharmacology- Pharmaceutics, Pharmacokinetics, Pharmacodynamic phases (First 1/2) (CL)

3 Phases of Drug Action
1.) Pharmaceutic
-Dissolution (Breaking down and Disintegrate)
2.) Pharmacokinetics
-Movement of medication through the body
3.) Pharmacodynamics

Pharmaceutic Phase
Tablet —–> Disintegration—–> Dissolution (now it’s a liquid)

What factors effect Dissolution?
-Tablets that contain other medications and excipients
-pH of the environment
>gastric secretions are acidic
>Meds that decrease gastric secretions
-Form of Medications
>Enteric coated/sustained release
>Suspensions
-Food
>Can increase or decrease absorption (more food
causes more acid production in the stomach)
-Age
>Young and old (Less acidic—>slower absorption)

Pharmacokinetic Phase
The pill can now move through the body
-Absorption
-Distribution
-Metabolism or Biotransformation
-Excretion or Elimination

Site of ORALLY administered drug absorption
SMALL INTESTINE is the most common site

Active Absorption
-Needs a carrier (enzyme or protein)
-Energy required
-Especially if it’s a water soluble pill, needs water to carry it
-Moves substances against concentration gradient

Passive Absorption
-Do not need a carrier
-No Energy needed. Effortless, no assistance needed to get into cell
-Movement from higher to lower concentration- DIFFUSION

Pinocytosis (Absorption)
-Enzyme engulfs the substance to carry it over to the cell
-Similar to Active Absorption but it engulfs it to carry it
-Energy REQUIRED
-Like a pacman or Leukocyte, comes along and eats it up and spits it back out

Lipid vs. water soluble
Lipid:
Easily passes through GI membrane
Water:
Needs a carrier

Non- Ionized vs. Ionized
Non-ionized:
Absorbs easily
Ionized:
Not as easily absorbed

Factors Affecting Absorption
-Blood flow ]
-Pain ]—–>the more—>the more absorption
-Stress _____ ]
-Body posture
-Exercise—->more exercising—>less acid stomach
-Fasting —->more alkaline
-Food —-> more acidic
-pH
-Age—>young&old—>less acid so slower absorption
-Site of administration

First-Pass Effect
-ONLY occurs with oral and rectal administration
-Does not occur to all oral medications
-Metabolism will cause some drugs to be
>inactive, remain the same, or metabolites
-First- Hepatic Pass- breaks down medication. Will NOT go into general circulation at full amount (not 100%)

Other routes of Administration
-Inhaled
-Topical
-Parenteral Not affected by the
-Sublingual FIRST PASS EFFECT
-Buccal
-Transdermal

Bio-availability
-Percentage of medication that reaches the systemic circulation
-Occurs after absorption and first-pass effect (hepatic drug metabolism)
-The bio-availability of IV medications is 100%
>IV is injected directly into the system. Does not
have a pharmaceutic phase

What affects Bio-availability?
-Drug form
-Route of administration
-GI mucosa (If they have a section of the GI tract
removed they will not absorb much)
-Motility (If they have diarrhea they may not absorb
much cause it would pass through too quickly)
-Food and other drugs (certain foods interact with
certain meds)
-Changes in liver metabolism
>Liver dysfunction
>Inadequate blood flow

Medication Distribution
Protein Binding—-> _________________________
Blood Flow———-> I Pharmacologic Effect I
Body Affinity——–> I_________________________I

Protein Binding
-The higher bound protein would get advantage over
the lower bound protein—>it would “get on the bus
first” while the lower bound becomes free drug
-Albumin—-“bus”
-Drugs in the Albumin (higher protein bound) are
passive drugs
-Lower protein drugs become free drug— all free drug
is active (doing work, being used) (This drugs level
will be high when a blood draw is taken)
-Protein bound drugs are unable to exert any effects
-Can’t have all the free drugs out at once, so they have
to switch out until the half- life is finished and it is
excreted
>Higher protein bound in the albumin will
eventually switch out and become free drug

Protein Binding Categories
-Highly Protein Bound- (>89%)- ex. Dixoin, Coumadin
-Moderately High Bound- (61-89%)
-Moderately Bound- (30-60%)
-Low Protein Bound- (<30%)

Factors Affecting Protein Binding
-Low Albumin —> means more free drug (bad)
-Age
-Weight —>You loose weight and you’ll have more free
drug if you weigh more you’ll have less
-Drugs that are highly protein bound

Overdose or Toxicity

Tissue Affinity
-Medication has an attraction for a specific organ or body part
-Blood Brain Barrier will only allow lipid soluble medication to cross
>When you’re pregnant, more soluble types will be
able to pass the blood brain barrier

Biotransformation (Metabolism)
-“chemical inactivation of a drug through its conversion
into a more water- soluble compound or into
metabolites that can be excreted from the body
-Primary site is the LIVER
-Process is detoxifying the body of the chemical
-It’s been absorbed and distributed, not it’s being
metabolized
-Not the same as the First-Hepatic Pass

Half Life (t 1/2)
-The time it takes for a medication to be eliminated by 1/2 or 50% of its original concentration
-Rate is based on a healthy adult
-Disease and age will affect the elimination
-The time it takes for half the dosage to be eliminated

Factors Affecting Excretion
-Acidic or alkaline urine (acidic urine will decrease excretion. Alkaline urine will increase excretion)
-Decrease in kidney perfusion
-Kidney disease
-Age—>kidney function decreases with age
-Fluid intake

Pharmacokinetic Review
-Medication Absorption, Distribution, Metabolism, and Excretion

Pharmacodynamic
-“study of drug concentration and its effects on the body”
-Complex process
-When they’re in the plasma doing their thing

Time Response Curve
-MTC – Minimum Toxic Concentration (don’t wanna give
over this level)
-MEC- Minimum Effective Concentration (don’t wanna
give less than this level)

Receptor Theory
-Kinase- linked receptors
-Ligated- gated ion channels
-G protein-coupled receptors systems
-Nuclear receptors
-2 drug agonists attach to the receptor site. The drug agonist that has an exact fit is a strong agonist and is more biologically active than the weak agonist
-Strong Agonist—> strongly effective, function at 100%
-Weak Agonist—->weakly effective, function at 50%

Drug Effects
-Non-specific
>Drugs that affect SIMILAR receptors at a variety of
sites
*ex. Bethanechol acts on the Cholinergi
receptors located in the bladder, heart, blood
vessels, stomach, bronchi, and eyes.
-Non-selective
>Drugs that affect DIFFERENT receptors along with
the targeted one
*ex. Epinephrine acts on three different
receptors: Alpha1, Beta1, and Beta2
receptors

Drug Action
-Stimulation or depression
-Replacement
-Inhibition or killing of organisms (antibiotics)
-Irritation (Laxatives)

Therapeutic Index and Range
-Mathematical Equation
-Measuring the minimum amount of medication administration to achieve therapeutic effect along with the minimum amount causing a toxic effect

Minimal lethal dose (LD)50% Don’t take when both
————————————– are 50%or it’ll kill you
Minimal effective dose (ED)50%

Low Therapeutic Index
Narrow margin of safety
-can easily cause toxic effects

High Therapeutic Index
Wide margin of safety
-Decrease in danger of causing toxic effects

Therapeutic Range (window)
Range between the minimum amount needed to cause an effect and minimum toxic concentration

Drug Levels
-Peak (high)
-Trough (low)
-Draw a T before a P on a Low Index medication
-Peak- highest concentration of the drug in your blood
stream
-Trough- Lowest concentration of the drug in your
blood stream

Loading Dose
-Large initial dose
-Purpose is to reach therapeutic levels quickly or
sooner
-ex. when given an antibiotic you are told to take
double the first time then the next dose take regular
amount

Side Effects
-Undesired effects of therapy
-Generally predictable
-Able to be tolerated
-Can cause discontinuation of medication if significant
-Educate patient

Adverse Drug Reactions (ADR)
-Undesirable
-Can cause harm
>Reversible to irreversible
-Unintended and unpredictable
-Can occur with normal dosing
-More severe than side effects
-Document and report

Toxic effects or Toxicity
-Medication in blood plasma is above therapeutic range
-Causes:
>Medication has low therapeutic index
>Drug overdose
>Combination of medications
>Alteration in absorption, metabolism, distribution,
or excretion

Pharmacogenetics
-Studies how drug action is affected by genetics or hereditary
>ex. when you and other family members have an
allergic reaction to the same medication
-Metabolism of medications altered

Tolerance
-Medications lose effectiveness
-Occur when taken for extended periods of time

Tachyphylaxis
-“rapid decrease in response to the drug”
-Common with narcotics and laxatives
-Acute tolerance to a drug

Placebo Effect
-Psychological belief
-A medication disguised as another but lacking chemical structure
-Used in drug trials
-Unethical
-“You think it’ll work so it works”

A client has liver and kidney disease. He is given a medication with a half-life of 30 hours. The nurse expects the duration of this medication to:

1.) increase
2.) decrease
3.) remain unchanged
4.) dissipate

1.) Increase

Because they have liver and kidney disease the half-life will have to be longer than a normal person

In older adults and those with renal dysfunction, the nurse knows that creatinine tolerance is usually:

1.) Substantially increased
2.) Slightly increased
3.) Decreased
4.) In the normal range

3.) Decreased

They’ll have decreased kidney function so therefore decreased creatinine clearance

Drug Interaction
-“an altered or modified action or effect as a result of interaction with one or more other drugs”
-Can occur in pharmacokinetic and pharmacodynamic phases
-ex. Elderly taking more than 1 medication at a time

Absorption
-Slowing down or speeding up emptying time of stomach contents
-Changes in gastric pH
-Potential formation of drug complexes
-Alteration in normal bacterial flora

Distribution
-Two drugs that are highly protein bound
-Decrease in serum albumin or protein plasma levels

Metabolism or Biotransformation
-Enzyme (hepatic) inducers:
>STIMULATES production of enzymes
>Metabolism of a drug is increased resulting in
excretion (the half life can be shorter)
>RESULT: MEDICATION IS DECREASED IN BLOOD
=less effectiveness of drug
-Enzyme (hepatic) inhibitors:
>DECREASES metabolism (in the liver) of specific
drugs

Excretion
-Increase or decrease in kidney function
-Change in urine pH

Therapeutic Drug Monitoring (TDM)
-Serum drug levels
-Digoxin is 0.5-2.0 ng/mL <----Therapeutic Drug level

Pharmacogynamic Interactions
-Additive Drug Effect
1+1=2
-Synergistic drug effect or potentiation
>One drug becomes stronger or more effective
1+2 = 2+1
-Antagonistic drug effect
1+1=0

Symptoms of drug- drug interactions
-Nausea
-GI upset
-Headache
-Dizziness
-Can be severe of life threatening
>Significant drop in BP or irregular heart rate
>Production of toxins that can damage vital organs

Drug-food interactions
-Absorption
>Increase
>Decrease
>Delay
-Empty stomach or with food
-Type of food
>Tyramine-rich foods such as cheese, wine, and
yogurt
>Foods high in vitamin K

Drug-Laboratory Interactions
-Abnormal electrolytes
-ex. Lasix decreases potassium levels as a result so you have to monitor it

Drug-Induced Photosensitivity
-Exposed skin has a reaction with sunlight
-Photoallergy
>Delayed hypersensitivity reaction
>Need to have previous exposure
>Antibodies are developed
-Phototoxicity
>Occurs 2-6 hours
>Erythema develops

Over the Counter Medications (OTC)
-No prescription needed
-Includes herbal remedies
-FDA monitors regularly
-Can be deadly (can inhibit or stimulate your prescribed drugs which can be deadly so always check PCP first)

FDA Regulations
-Monitors drug safety
-Establishes mandatory labeling
-3 Categories:
1.) Safe and Effective
2.) Either Unsafe or Ineffective
-Not marketed unless reaches category 1
3.) Can’t determine safety or efficacy

Polypharmacy
Administration of many drugs together
-Can be OTC or prescription
-Occurs more with the elderly

Cautions in use of OTC medications
-Delay in professional diagnosis and treatment
-Symptoms may be masked
-Read labels
-Consult health care provider before use
-Inactive ingredients may cause adverse reactions
-Potential for overdose
-Intentions of prescription and OTC medicines
-Polypharmacy

Nursing Implications
-Nurses must be aware of current drug information
-Changes in FDA recommendations
-Patient education of drug information and resources
-Teach your patients to speak up , ask questions, find the facts, evaluate their choices, and read the labels.
-Encourage patients to use only one pharmacy if at all possible

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