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Pharmacology > 1st lecture - pharmacokinetics > Flashcards

1st lecture - pharmacokinetics Flashcards

1
Q

define Pharmacology

A

the study of the actions of drugs on the normal or pathologically altered function of the organism.

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2
Q

A drug is

A

any combination of substances that is intended for the purpose of prevention, diagnosis, treatment or alleviation of an illness or symptom of illness on a human or animal or for the restoration or alteration of functions in a human or animal.

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3
Q

define Pharmacokinetics

A

all processes that define the existence and movement of a drug in an organism:

“adbe”
1. absorption
2. distribution (metabolism)
3. biotransformation
4. excretion

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4
Q

What are pharmacokinetics for? (3)

A

helps understand the behaviour of drugs inside the organism.

helps explain undesired responses

helps find the right drug, dose, route of administration and interval for administration.

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5
Q

Withdrawal period?

A

time from last administration of drug, until the time of animal product use (meat, milk, eggs etc.).

“varoaika”

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6
Q

The primary use of pharmacokinetics in a clinical setting is to

A

calculate safe and effective drug dosage regimens for patients.

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7
Q

effective drug dosage regimens are generally based on

A

target plasma drug concentrations that are believed to be therapeutically effective.

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8
Q

To maintain that target concentration, what is important (2)

A

the dose and dosage interval are important.

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9
Q

Methods of Systemic administration broadly (2)

A

Parenteral/outside the GI tract (IV; IM; SC; inhalation)
Enteral (PO)

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10
Q

Methods of Local administration (4)

A

On the skin
On mucous membranes
Intp the udder
Into the uterus
+ Elsewhere – for instance: epidural administration

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11
Q

name 4 methods of parenteral administration

A

IV; IM; SC; inhalation

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12
Q

Factors impacting absorption/ impact the penetration of the membranes (4)

A
  1. drug molecule properties
  2. membrane properties
  3. pH in place of absorption
  4. local blood supply
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13
Q

drug molecule properties (5)

A
  1. Lipid solubility
  2. The nature (anion, cation, non ionising)
  3. Degree of ionisation
  4. pH
  5. Pharmaceutical form
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14
Q

Diffusion

A

the property of molecules to move from the higher concentration towards the lower concentration.

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15
Q

Pinocytosis

A

an active, energy consuming process where extracellular fluid and solutes are taken up into a cell via small vesicles / transport of liquid droplets

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15
Q

Phagocytosis
and give example

A

transport of solid particles
(e.g. immunoglobulins in milk)

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16
Q

Degree of dissociation indicates

A

how much of a drug is dissociated (broken down into ions)
/
the extent to which the dissociation occurs.

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17
Q

what type of molecule absorbs more easily

A

Non- ionised - lipid soluble

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18
Q

“Acid-base conflict, ionic lock” refers to what

A

Such as in the rumen – some drugs cannot be administered per os to ruminants; since bacteria inactivate the drug, drug can be locked in rumen, diluted.

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19
Q

What type of animals cannot receive systemic drugs PO?

A

ruminants

Exception: Specific pharmaceutical forms that stay in the rumen for a long period and release the active ingredient gradually.

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20
Q

pH partition

A

pH partition is the tendency for acids to accumulate in basic fluid compartments, and bases to accumulate in acidic compartments.

For example, in ruminants, many basic drugs tend to distribute into the rumen, resulting in distribution volumes much larger than those in monogastrics.

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21
Q

pH partitioning phenomenon is important in

A

absorption, but also in any situation where the pH of fluid compartments across a biological membrane is different.

“It will occur for a drug distributing from plasma (pH=7.4), to milk (pH=6.5-6.8), to cerebrospinal fluid (pH=7.3) or intracellular sites (pH=7.0).”

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22
Q

General rule: weak acid drugs (ie. aspirin) are readily absorbed from

A

acidic environment (from GI tract (pH 1,5) to blood (pH 7,4));

weak base drugs (ie. morphine, ketamine) are absorbed from alkaline environment and trapped in an acidic environment (very poor absorption from GI).

23
Q

General rule: weak base drugs (ie. morphine, ketamine) are absorbed from

A

alkaline environment and trapped in an acidic environment (very poor absorption from GI).

weak acid drugs (ie. aspirin) are readily absorbed from acidic environment (from GI tract (pH 1,5) to blood (pH 7,4)).

24
Q

The following 2 are prerequisites for absorption through a cell membrane:

A

Low molecular weight
Lipid solubility

25
Q

how does Improved blood supply affect drug pharmacokinetics?

A

faster absorption

26
Q

Bioavailability is

A

the fraction (%) of an administered drug that reaches the systemic circulation.

27
Q

When drug is administered per os, the bioavailability may be influenced by

A

the fullness of the gastrointestinal tract; differences between animal species.

28
Q

the primary site for most drug absorption is

A

the small intestine

29
Q

The drug moves from the stomach and small intestine to the

A

liver via the portal circulation

30
Q

Pharmacokinetics:
some drug additives increase what

A

absorption,
some inhibit absorption.

31
Q

3 important points in regard to Absorption from subcutaneous tissue and muscle

A
  1. Blood supply in the site of administration
  2. Aqueous solutions absorb faster, oleaginous solutions absorb slower (fat soluble)
  3. Prolonged effect via this route because absorption takes time
32
Q

Oleaginous Solutions are

A

oh-lee-aj-i-nuss

fat soluble solutions

33
Q

forms of drug for Absorption from the lungs (3)

A

Gases, aerosols, vapours

34
Q

What stage follows the absorption stage

A

Distribution stage follows, except in case of administration into the blood vessel
(in that case no absorption occurs because its literally already in the blood)

35
Q

Factors impacting distribution (4)

A
  1. Binding of the drug with the blood plasma proteins and formed blood elements
  2. Physical-chemical drug properties
  3. Blood supply of the organ
  4. Tissue affinity
36
Q

where is the effective portion of drug in the blood

A

The free fraction achieves the effect, the bound fraction is not free to bind target tissues if its bound to a transport protein.

37
Q

Tissue affinity in the context of pharmacology is

A

Specific sensitivity of tissues with respect to certain medication.

38
Q

Tissue affinity/specific sensitivity of Aminoglycosides (a group of ab)

A

kidneys

39
Q

Tissue affinity/specific sensitivity of Tetracyclines

A

bones, including teeth

capable of destroying bones in young animals so long courses should be avoided in growing animals.

40
Q

Volume of distribution refers to

A

the theoretical volume that the total amount of administered drug would have to occupy to provide the same concentration as it currently is in blood plasma.

The volume of distribution (Vd) is a pharmacokinetic parameter representing an individual drug’s propensity to either remain in the plasma or redistribute to other tissue compartments.

41
Q

what compounds can penetrate the blood-brain barrier

A

small enough nonionized lipid-soluble compounds

ie. small polar molecules like glucose

42
Q

Before elimination, what takes place

A

Biotransformation – transformation of the drug into metabolites through chemical reactions

43
Q

Elimination includes what two processes?

A

biotransformation and excretion

44
Q

Biotransformation mainly occurs in ?
And to a lesser extent in (4)?

A

It mainly occurs in the liver,
to a lesser extent also in the intestines, kidneys, lungs, blood plasma.

45
Q

The primary liver enzymes that participate in biotransformation are the following:

A

oxidases, reductases, transferases.

46
Q

What does the following describe:
The drug that passes through the liver then goes into the gall bladder and it may be absorbed back from the gall bladder or the intestinal tract, getting back into the liver through the hepatic portal vein.

A

Enterohepatic circulation (recycling)

47
Q

explain secondary peak in plasma concentration

A

Compounds that are excreted into bile may have a prolonged stay in the body because of continuous opportunity for intestinal reabsorbtion via the enterohepatic circulation.

48
Q

explain First-pass metabolism

A

The degree of metabolic breakdown of an orally administered drug that occurs in the intestine or liver before it reaches the systemic circulation.

It is also known as the first-pass effect and results in a reduction in the concentration of the drug.

49
Q

Excretion usually occurs through (3)

A

1) the kidneys
2) the intestines via feces
3) the lungs

In addition, possible through: mucous membranes & glands
(sweat glands, sebaceous glands, mammary glands, biliary excretion)

50
Q

explain organ clearance

A

the volume of blood or plasma that an individual organ clears over a unit of time

51
Q

explain total clearance

A

the volume of blood or plasma that an organism clears over a unit of time,
= “the sum of organ clearances”

Thus, total body clearance is equal to the sum clearance of the substance by each organ.

52
Q

explain Half-life, T1/2

A

the period of time over which the concentration of a drug is reduced by 50% in the blood.

53
Q

Half-life depends on (3)

A

the animal species,
the particular nature of the tissue,
the method of administration.

54
Q

the aim of Interspecies extrapolations of pharmacokinetics is

A

to predict drug activity or toxicity in a new species not previously studied.

55
Q

2 difficulties with Interspecies extrapolations of pharmacokinetics

A
  1. a drug’s pharmacokinetic profile does not extrapolate without ajusting for species characteristics
  2. the pharmacodynamic response may be very different across species
56
Q

difference between pharmacokinetics and pharmacodynamics?

A

pharmacokinetics is the movement of drugs through the body, whereas pharmacodynamics is the body’s biological response to drugs.

Pharmacology (19 decks)

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