Pharmakokinetics Flashcards
Test I Review
The study of the movement of drugs throughout the body.
Pharmacokinetics
When solid drugs are administered, it is dissolved in ______ before it is absorbed into the blood.
Gastric or intestinal fluid.
True or False?
Administering a fluid with a solid drug speeds up the rate of absorption.
True
The term used to describe the efficiency of absorption into the blood of a particular drug form.
Bioavailability
If two different drug formulations go into the blood with the same efficiency they are said to be?
Bioequivalent
Pharmacokinetics involves four(4)processes :
i. absorption
ii. distribution
iii. metabolism
iv. excretion
Pharmacokinetics involves four processes that determines? (6)
i. serum drug levels
ii. onset of drug action
iii. peak serum level
iv. duration of action of a drug
v. drug half-life
vi. therapeutic and toxic effects of drugs
The process by which a drug passes from its site of administration into fluids of the body that will take it to the site of action
Absorption
The routes mainly used for drug administration.
Oral and parenteral routes
Factor that affect absorption in:
Oral route
i. Presence of food
ii. Food from some food groups
iii. Acidity of stomach
Factor that affect absorption in:
Parenteral routes
i. IV administration
ii. subcutaneous administration
iii. intramuscular
True or False:
In parenterally applied medication, application of heat or massage decreases absorption, while cold packs or compression increase absorption.
False. Heat/massage increase absorption, cold/compression decreases absoprtion.
Injection of ________ at the site of the injection (of the medication) constricts blood flow to the area and thus decreases absorption.
epinephrine
True or False?
Too long needles used for intramuscular drug administration delivers the drug to the subcutaneous tissue not the muscle.
False. Too “short”.
______________ has an unpredictable absorption pattern, so this route is only used when others are not feasible (e.g. in the presence of severe nausea, vomiting) or the drug is require in the lower intestine. To ensure correct absorption, the nurse must check the drug label for correct drug insertion technique.
Rectal administration of drug
Other routes of administration include __(4)__. These routes are useful to protect drugs from chemical decomposition in the stomach and liver.
- Sublingual
- Translingual (on the surface of the tongue) and 3. Buccal and
- Transdermal routes.
Factors that affect Absorption of a drug include: (13)
I. Size of drug molecules II. Physical state III. Properties of the drug IV. Environmental temperature V. State of absorption site VI. Membrane thickness VII. Surface area of body VIII. Blood supply at absorption site IX. Route of administration X. Compliance XI. Presence of food or other drugs in GIT XII. Formulation – enteric, slow release Xlll. Drug forms
True or False?
Liquid drug forms are faster absorbed than capsule and pills.
True
____ alllows absorptions into systemic circulation.
Mucosa
- Involves the transport of drug molecules within the body from the site of absorption to the site of drug action.
- It depends on adequacy of blood circulation: organ with extensive blood supply receives the drug very quickly (e.g., heart, liver, kidney and brain), areas such as muscles, skin and fat receive body supply more slowly.
DISTRIBUTION
Flow of Distribution of the Drug
Drug -> Blood Plasma and/or Tissue fluid -> Site of action of drug
Distribution in the CNS is limited by the?
Blood-Brain-Barrier.
True or False?
Most drug cross the placenta and can affect the foetus.
True
True or False?
Route of administration affects drug distribution.
True
Oral drug go to the liver first and the liver starts breaking down the drug. Hence, less active drug goes into the general circulation for distribution to tissue. This phenomenon is known as the?
“first pass effect.”
Drugs that are highly soluble in fats may accumulate quickly in _____.
Fats
True or False?
Many drugs enter breast milk.
True
Factors that affect distribution: (5)
i. Plasma protein binding
ii. Regional blood flow (vascularity)
iii. Anatomical barrier – blood-brain or blood-placental barrier
iv. Disease
v. Lipid solubility
The _____ route is used to administer certain medications which cannot cross barriers when given intravenously or orally.
- For example, in the administration of gentamicin for meningitis, this antibiotic is administered intrathecally because it cannot cross the blood-brain- barrier when given by IV route.
The intrathecal route.
_____ drugs form a complex with plasma protein, particularly albumin.
Lipid drugs
Drugs bound to protein are _______; they do not leave the blood stream.
Pharmacologically inactive
Protein binding slows drug metabolism, thus reducing the risk of ______.
Drug toxicity.
True or False?
If two drugs (A and B) are administered simultaneously and they use the same carrier, displacement of one of the drugs (say A) may occur causing more unbound A than B drug to move freely in and out of the blood.
- Example: warfarin administered with aspirin leads to much more free warfarin than in the absence of aspirin –> increase risk of bleeding.
True
Drugs bound to plasma proteins have ______ in the body than unbound drugs.
Longer duration of action
Note that ___(a)__, and in particular, __(b)____, adversely affects drug distribution.
a. hypoproteinemia
b. hypoalbuminemia
Factors that lower blood protein levels include: (8)
Malnutrition, starvation, Crohn’s disease, ulcerative colitis, celiac disease, cystic fibrosis, liver and renal disease, etc
______ application gives minimal absorption into systemic circulation.
Topical Application
True or False?
IM gives 100% bioavailability
False. IV gives 100% bioavailability.
Oral dose gives < 100 bioavailability because of?
First pass effect
Oral dose with food or antagonistic drug gives ______ bioavailability.
< 100%
- The ability of the living organism to modify the chemical structure of drug
- Occurs mainly in the liver, kidney and lungs
Biotransformation (Metabolism)
Is the process by which drugs are biotransformed by the body to make then water soluble and ready for excretion by the body
Metabolism
This causes a potent drug to be inactivated before it stored in the body
Biotransformation
It converts lipid soluble drugs to water-soluble forms so that they may be excreted by the kidney.
Metabolism
Most drugs are metabolized by enzymes in the liver called _____ system or ____ system.
- Cytochrome P450 (CYP) system or
2. Microsomal enzymes system.
Some drugs are metabolized by ____ in RBC, kidney, lungs, GI, mucosa and plasma.
Enzymes
Metabolism of a drug can produce ___ and _____.
- Active metabolites
2. Inactive metabolites.
Metabolites that can exert pharmacologic effect of cells.
- Active metabolites
Metabolites that has no pharmacologic activity
- Inactive metabolites.
Certain drugs can increase the levels of _____, while others have no effect or can lower it.
Microsomal enzymes
When the microsomal enzymes levels increase the enzymes _____ any drug that reaches the liver much faster than normal.
- Break down
When the microsomal enzymes level _____ drugs reaching the liver are metabolized less slowly than normal.
Decrease
_____ of a drug increases the risk of toxicity of the drug, e.g., acetaminophen toxicity
Rapid Metabolism
Some drugs inhibit metabolic enzymes, thus ____ the metabolism system, e.g., cimetidine.
Slowing down
Rate of metabolism is decreased in _____.
Infants and the elderly
Rate of metabolism is decreased in the presence of (2).
Impaired blood flow and low protein intake.
Factors that affect biotransformation include: (4)
- Site of drug metabolism –liver, kidney, lung
- Genetic factor
- Other drugs presence
- Age
Refers to the elimination of the drug from the body.
- It requires adequate function of CVS, kidney, bowel, lung, and skin.
Excretion
Factors affecting the excretion of drug:(4)
i. Age
ii. Organ status
iii. Site of drug excretion – kidney, GIT, lungs, sweat glands, mammary glands
iv. pH of urine
Drug action can be described by ____ and it’s graphical distribution over time.
Half-life
A lab measurement of the amount of a drug in the blood at any particular time.
Serum blood level
It is determined by dosage, absorption, bioavailability, half-life of the drug, rate of metabolism and excretion.
Half-life
Time interval required for the plasma concentration to half of its peak concentration.
Half-life
The half-life measure the rate of ___ of a drug from the body.
Rate of elimination
The distribution curve depends on the ____ .
Route of administration.
With ____ doses, the curve rise from zero to a maximum (peak plasma concentration) then falls of gradually. This curve appears to be skewed to the left. Subq. route and intramuscular routes have almost the same curve while, IV route has as much different curve shape.
Oral doses
Subq. route and intramuscular routes have almost the same curve as the oral route.. while, ____ route has as much different curve shape.
IV route
- determined by dose and absorption into the blood
- is the minimum quantity of the drug require to exert pharmacologic action on the body.
Minimum Effective Concentration (MEC)
- excess level at which drug causes adverse effects (toxic effects)
- may arise from single on multiple doses given or slow metabolism that causes accumulation of drug in tissue
Toxic concentration
Region for effective therapy
Therapeutic Region
Highest conc. of drug in the plasma
Peak
Time it takes for a drug to exert its therapeutic effects
Onset
The length of time a drug exhibits a pharmacologic effect after administration.
Duration
Nursing Interventions for Drug Therapy (4)
- Monitoring response of client on Drug therapy
- Observe client for manifestation of desired effects.
- Monitor client to detect adverse effects
- Measure biochemical changes which reflect the drug’s activity (e.g., measure plasma volume of the drug).
Factors that affect response to Drug Therapy
- Dose
- Frequency of administration
- Food
- Interaction with other drugs (potentiation, synergism, incompatibility)
- Speed of absorption
- Metabolic rate
- Genetic
- Rate of excretion
- Health status
- Herbal medication
Factors that contribute to individual variation to drug response include: (11)
- Age
- Gender
- Body weight and body surface area
- Basal metabolic rate
- Disease state
- Genetic factors
- Placebo effect
- Time of administration
- Tolerance
- Environmental factors
- Idiosyncratic responses
“What the PT do to the drug”
Pharmacokinetics
True or False?
A drug can’t have a systemic effect if it doesn’t go into the blood.
True
This tells how frequently the drug is going to be administered.
Half-life
