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Pharmaceutics Exam 1 > Part 4 > Flashcards

Part 4 Flashcards

1
Q

What is biopharmaceutics?

A

The area of pharmaceutics embracing the relationship between the physical, chemical, and biological sciences as they apply to drugs, dosage forms, and drug action

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2
Q

What is another word for metabolism

A

biotransformation

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3
Q

If a drug has an oral route of administration, explain its movement throughout the body

A

gastrointestinal tract. from there, some of the drug is absorbed into the circulatory system, from which the drug either enters the tissues (fluids and organs) or metabolic sites. At metabolic sites, the drug is excreted as metabolites. If excreted upon return to the circulatory system, it is excreted through the kidneys

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4
Q

Once a drug is administered and absorption begins, does the drug remain in a single body location?

A

no — it is distributed throughout the body until its ultimate elimination

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5
Q

Drugs administered by intravenous route are introduced where?

A

in the circulatory system, avoiding absorption (which is required in order for systemic effects to occur in all other routes of administration

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6
Q

In intramuscular and subcutaneous injections, where is the drug being introduced?

A

at the tissues. From there it goes into circulation/GI tract

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7
Q

Most drugs pass through biological membranes by….

A

PASSIVE DIFFUSION

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8
Q

Explain what passive diffusion is

A

The membrane does NOT actively participate in the process. The absorption process is driven by the concentration gradient— the drug comes from the side with high concentration

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9
Q

Explain what Fick’s first law is

A

Fick’s first law states that the rate of diffusion across a membrane is proportional to the difference in drug concentration on both sides of the membrane

-dc/dt = P(C1-C2)

C1 and C2 are the drug concentrations on each side of the membrane (C1 is the compartment with the greater concentration of the drug)

P is a permeability coefficient/constant

-dc/dt is the rate of diffusion/transport across the membrane

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10
Q

C1 usually represents ___ and c2 ___

A

C1 — compartment with higher drug concentration. ie: the absorption site

C2 — concentration of drug in the blood

C1 is usually MUCH greater due to the rapid dilution of the drug in the blood and its subsequent distribution into the tissues.

so, for practical purposes, fick’s law can just be:::

-dc/dt - PC1

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11
Q

The gastrointestinal absorption of most drugs occurs in accordance with _________ kinetics

A

1st order

the rate depends on drug concentration. Doubling the dose doubles the transfer rate

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12
Q

What is the permeability coefficient?

A

The rate at which a substance (drug) moves through a permeable membrane

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13
Q

What does a high permeability coefficient mean

A

that the drug will diffuse across the membrane very rapidly

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14
Q

Name 3 things that affect the permeability coefficient/constant

A
  1. The diffusion coefficient of the drug
  2. The thickness and area of the absorbing membrane
  3. The permeability of the membrane to the particular drug
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15
Q

The cell membrane is highly permeable to…

A

LIPID SOLUBLE SUBSTANCES

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16
Q

The Henderson-Hasselbach equation measures…

A

the extent of ionization of a drug

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17
Q

Are most drugs strong or weak acids/bases

A

most drugs are weak acids/bases because they are more lipid soluble and can cross the membrane easier

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18
Q

Explain how passive transport may be different from specialized transport

A

specialized transport may be slower. this is so because the carrier molecules across the membrane may become completely bound with the substance to be transported

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19
Q

What is active transport (absorption)

A

a subcategory of specialized transport.
the drug is carried AGAINST its concentration gradient

substrate forms a complex with the carrier in the membrane surface.

Substrate-carrier complex moves through the membrane. Substrate is released from the complex at the other side of the membrane

carrier molecule is now free and returns to the apical surface of the membrane, ready to bind further substrates

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20
Q

What is facilitated diffusion

A

along with active transport, the substance is moved across the membrane through a carrier molecule, but the process does NOT require energy as it is moving with its concentration gradient

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21
Q

Does active absorption require energy?

A

yes

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22
Q

For a drug to be absorbed it must first be….

A

dissolved in the fluid at the absorption site

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23
Q

the process by which a drug particle is dissolved is termed….

A

dissolution

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24
Q

Which has a larger surface area – the stomach or the small intestine

A

the small intestine

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25
Q

What is the MAJOR absorption site

A

the small intestine

26
Q

What is gastric emptying time

A

the amount of time it takes for the drug to leave the stomach and begin absorption in the small intestine

27
Q

Name 6 factors affecting dissolution (and hence drug absorption)

A

-particle size (smaller particle size = faster dissolution)
-surface area (larger surface area = fast dissolution)
-crystal or amorphous drug form (amorphous = fast dissolution. crystalline is more stable and requires more energy to dissolve)
-salt forms (salt forms are ionized and dissolve faster)
-state of hydration (anhydrous form is less stable and has a fast dissolution rate)
-condition of the environment (ie: pH, tetracycline forms a complex with calcium which causes solubility to decrease)

28
Q

What does bioavailability mean

A

“bioavailability” describes the rate and extent to which an active drug ingredient is absorbed from a drug product and becomes available at the site of action

29
Q

What does bioequivalence mean

A

the term bioequivalence refers to the COMPARISON of bioavailabilities of different formulations, drug products, or even batches of the same drug product

30
Q

Graphically, bioavailability of a drug is portrayed by……

A

a blood, serum, or plasma concentration time curve

31
Q

Give scenarios in which a bioavailability study would have to be submitted

A

NDA
ANDA
SNDA

32
Q

Plasma profile has which 3 key features

A

-peak height (C max)
-time of peak (Tmax)
-Area under the serum-concentration time curve (AUC)

33
Q

Most drugs exhibit their therapeutic effect through _____ circulation. Receptor sites are available through…

A

systemic
systemic circulation

34
Q

Are we able to measure drug concentration at the receptor site?

A

no - not at this point

That’s why we measure the amount of drug in the PLASMA and try to correlate that to the amount at the receptor site

35
Q

What are the factors influencing drug availability (bioavailability)

A

rate and extent of absorption

36
Q

Are we concerned with bioavailability in drugs with an intravenous route of administration?

A

NO
The drug is placed directly into systemic circulation. The bioavailability for intravenous routes is this almost always 100%

37
Q

Are we concerned with bioavailability in drugs with an extravascular route of administration?

A

YES — because the drug doesn’t reach systemic circulation until after it is absorbed

38
Q

the plasma profile curve is ___ vs ___

A

concentration vs time

39
Q

What is Cmax

A

the peak concentration of the drug in the serum

40
Q

what is tmax

A

the TIME at which cmax occurred (ie: 2 hours after administration)

41
Q

plasma profile usually follows ____ order kinetics

A

1st order

42
Q

Explain the concept of a half life of a drug

A

if the half life of a drug is 3 hours, after 3 hours, 50% of the drug will remain in the body. After another 3 hours, 25% of the drug will remain in the body, etc

43
Q

In conducting a bioavailability study, we want the sampling time to be at least ____ half lives of the API

A

3

44
Q

When drug concentration is decreasing at the absorption site, where is it going?

A

into the body

45
Q

When a drug becomes a metabolite, what organ did this happen in

A

through the liver

46
Q

A bioavailability study can be conducted using ___ or ___, and it is difficult to do with ___

A

a bioavailabilty study is conducted using blood or plasma, but it is difficult to do with urine

47
Q

What factors on the plasma profile have to do with the RATE of absorption

A

Cmax
Tmax

48
Q

What factor on the plasma profile has to do with the EXTENT of absorption

A

the area under the curve – tells the amount of drug absorbed into circulation

49
Q

The smaller the AUC, the _____ drug being absorbed

A

LESS

50
Q

Relative bioavailability is used for comparing bioavailability of drug products. Give 3 examples

A

-extravascular dose vs intravenous dose
-same product made by 2 diff manufacturers
-same drug in different dosage forms. ie: tab vs solution

51
Q

How do we determine relative bioavailability

A

F = AUCtest/AUCreference

AUC test = product whose bioavailability is being determined

AUC reference - standard against which the test is being evaluated

BOTH PRODUCTS MUST BE ADMINISTERED AT THE SAME DOSE

52
Q

For a NEW PRODUCT intended for extravascular administration, what will the reference AUC be to determine bioavailability?

A

the INTRAVENOUS DOSE of the product
This is called ABSOLUTE bioavailability

53
Q

If testing drugs made by 2 different manufacturers, what will the reference bioavailability be?

A

the innovator’s product (brand name – co. who discovered it)
This is RELATIVE bioavailability

54
Q

For the same drug marketed as different dosage forms, what will the reference bioavailability be?

A

the reference is the EXISTING dosage form of the product
This is RELATIVE BIOAVAILABILITY (absolute is extravascular compared to IV)

55
Q

How do you determine absolute bioavailability

A

F = AUC test/D test / AUCIV/DIV

test product = product whose bioavailability is being determined

reference = intravenous dose of the product

F = fraction of dose administered that reaches systemic circulation

56
Q

Name the drug substance physiochemical properties that influence the bioavailability of oral drugs

A

-particle size
-crystalline or amorphous form
-salt form
-hydration
-lipid or water solubility
-pH and pKa

57
Q

Name the pharmaceutical ingredient factors that influence the bioavailability of oral drugs

A

-fillers
-binders
-coatings
-disintegrating agents
-lubricants
-suspending agents
-surface active agents
-flavoring agents
-coloring agents
-preservative agents
-stabilizing agents

58
Q

Name the dosage form characteristics that influence the bioavailability of oral drugs

A

-disintegration rate (for tablets)
-dissolution time
-product age and storage conditions

59
Q

Name the physiological factors and patient characteristics that influence the bioavailability of oral drugs

A

-gastric emptying time
-intestinal transit time
-gastrointestinal abnormality or pathologic condition
-gastric contents
-other drugs
-food (ie: tetracycline bonding to calcium)
-fluids
-gastrointestinal pH

60
Q

The longer the gastric emptying time, the _____ the absorption

A

less

61
Q
A

Pharmaceutics Exam 1 (8 decks)

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