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Pharmacology/LC > All LC pharma > Flashcards

All LC pharma Flashcards

1
Q

Example of Over the counter product

A

Lotrimin AF (Miconazole, spray)

Lotrimin AF (Clotrimazole, cream)

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2
Q

What is meant by over-the counter?

A

similar brand name different active ingrediant

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3
Q

why should we use generic and not brand name?

A

1) single drug multiple brand name (overdosing)
2) Over the counter product (same brand name different active ingrediant)
3) endanger international travelers

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4
Q

how do we excrete lipophilic drugs

A

they get metabolized in the liver and become hydrophilic via adding more structures to it

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5
Q

how does the pH of the medium affects a drug absorption? remember for a drug to become lipophilic it should be unionized

A

wek acidic drugs are absorbed better in the stomach as they are found in their unionized for there while weak base drug do the same in the intestine

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6
Q

what are the factors affecting drug absorption?

A

1) drug properties (lipid solubility, polarity, & molecular weight)
2) route of administration
3) blood flow to the absorption site
4) total SA available for absorbtion
5) Contact time at absorption surface
Expression of P-glycoproteins (P-glycoprotein is a transmembrane transporter protein throughout the body, including the liver, kidneys, placenta, intestines, and brain capillaries, and is involved in transportation of drugs from tissues to blood.
)

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7
Q

what are the types of enteric-coated tablets?

A

Acid resistant (allows absorption in intestine)
Alkaline sensitive (dissolves in upper intestine)
aspirin is coated to reduce the side effects

coatings either protects drug from stomach or stomach from drug (ulcers

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8
Q

sustained release tablets

A

Designed to slowly release drug from the formulation ->
 rate of dissolution
 rate of absorption
 frequency of dosing

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9
Q

what is the effect of adrenaline on drug absorbance?

A

it decreases it as it causes vasoconstriction

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10
Q

which drugs are absorbed faster?

A

Inhalation→Sublingual→Rectal→intramuscular→subcutaneous→oral→transdermal

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11
Q

what does the area under the graph in the bioavailibity determination emphasizes?

A

extent of drug absorption

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12
Q

how can you calculate the bioavailibity of a drug from oral and iv graphs?

A

Area under the curve (oral/area under the curve IV) *100

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13
Q

what is meant by the therapeutic range?

A

the area between minimum effective concentration and minimum toxic concentration

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14
Q

what is meant by onset?

A

the time when the drug is given till it reaches the minimum effective concentration

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15
Q

what is meant by the duration of action?

A

it is the time from onset till it goes below the MEC again

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16
Q

what is the meaning of Bioequivalence,

A

we use it to describe two drugs, we say that drugs are bioequivalent if they have the same bioavailability and take similar timing to reach peak blood concentration.

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17
Q

what is the meaning of (blood brain barrier)

A
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18
Q

what is the meaning of volume of distribution,

A

Volume of distribution (Vd) = amount of drug in the body/ plasma concentration at time 0

                                 OR

F (Bioavailability) * Dose / TC (target plasma concentration) = Vd

it tells us how extensively the drug is distributed to the rest of the body compared to the plasma

so for example you take a certain volume of water and a certain mass of drug, then divide the mass of the drug by the volume of liquid you will get C=mg/L

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19
Q

what are the factors that affect drug distribution?

A

1) blood flow (brain, liver & kidney has the highest BFlow)
2) capillary permeability
3) binding of the drug to plasma proteins and tissues (may cause drug accumulation in tissue)
4) lipophilicity of the drug
5) volume of distribution

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20
Q

what is meant by a loading dose?

A

the extra dosage is given initially to go beyond the MEC and below MTC then as it comes down again we give extra dosages at certain time intervals to always be above the MEC

Dose = Vd * TC / F

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21
Q

what is meant by pharmaceutical equivalents?

A

same active ingredient but one has a brand and the other is generic, they could be differences in
1: drug particle size
2: excipients
3: manufacturing equipment/process
4: site of manufacturing

they could have different bioavailability and be bioinequivelant

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22
Q

how to calculate a dosage?

A

you multiply the effective drug with its volume of distribution (Vd)

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23
Q

which drugs have the lowest Vd?

A

drugs restricted to the vascular compartments, as they are large, charged, and often protein bound like warfarin: 9.8L

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24
Q

which drugs have the highest Vd?

A

Drugs that accumulate in the tissues, as they are small, lipophilic, and unevenly distributed like chloroquine: 13000L

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25
Q

what are the implications caused by the plasma protein binding?

A

1) Highly PPB drugs have low Vd
2) Drugs bound to the PPB are not available for action
3) there is an equilibration between bound and not bound drug

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26
Q

which drug has a high PPB?

A

Aspirin and it can be used to replace other drugs and bile “drug-drug interaction”

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27
Q

what should you do in a case of hypoalbuminemia?

A

adjust dosage as previously the bounded drug to proteins in the plasma will now enter the tissue so it might cause toxicity

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28
Q

What are the factors affecting the Vd?

A

1) Lipid solubility (lipid: water partition coefficient)
2) pKa of the drug
3) Affinity for different tissues
4) Blood flow
5) Disease states
6) Plasma protein binding

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29
Q

what is meant by biotransformation?

A

the conversion of non-polar lipid-soluble compounds to polar lipid-insoluble compounds to avoid reabsorption in renal tubules and enhance excretion

this protects the body from toxic metabolites

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30
Q

which drugs become more active after biotransformation?

A

morphine to morphine-6-glucuronide

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31
Q

what drug changes from inactive to active after biotransformation?

A

levodopa to dopamine

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32
Q

which drug changes from non-toxic to more toxic metabolites?

A

isoniazid to acetyl isoniazid

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33
Q

What are the phases in biotransformation?

A

1) metabolites become either active/unchanged or inactivate (oxid, reduced, and hydrolyzed) involving the cytochrome P-450 system “CYP1, CYP2 and CYP3” (microsomal mixed function oxidases)

basically, it make the drug more polar by introducing or unmasking a polar group (-OH, -NH2)

2) some drugs directly enter this phase, and metabolites are inactive (Morphine-6 glucuronide is an exception (the liver conjugates the oxidized product to make it water soluble))

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34
Q

which cytochromes carries the largest drug biotransformation?

A

CYP3A4/5 Found in the liver, intestine & kidney

35
Q

what are the drugs capable of increasing the synthesis of one or ore CYP isozyme?

A

1) phenobarbital (used for sleep & sedative)
2) rifampin (antibiotic)
3) carbamazepine

Causing significant decreases in plasma concentrations of drugs metabolized by these CYP isozymes

36
Q

which drugs inhibit CYP- biotransformations?

A

erythromycin
ketoconazole
ritonavir

mainly by their competition for the same isozyme

37
Q

what are the drugs that are oxidized by non-microsomal enzymes?

A

1) alcohol – Dehydrogenase

2) Adrenaline – Monoamine oxidases (MAO) and catechol-o-methyltransferase (COMT)

) Mercaptopurine – Xanthine oxidase

38
Q

in phase two metabolism, what are the endogenous substrates added to the drug to make it highly water soluble?

A

1) Glucuronic acid
2) Sulfuric acid
3) Acetic acid
4) amino acid

39
Q

what are the factors that affect the biotransformation of drugs?

A

1) Concurrent use of drugs (induction & inhibitors)
2) Genetic polymorphism
3) Pollutants
4) Pathological status
5) Age

40
Q

what is meant by half-life?

A

it is the time required to decrease the amount of drug in your body by 1/2 during elimination

41
Q

what is meant by first-order kinets?

A

when a constant fraction (percentage) of drug is metabolized per unit time

rate of drug elimination is proportional to plasma concentration

EXPONENTIAL GRAPH (VERY IMP)

42
Q

What is meant by zero-order kinetics?

A

when a constant amount of drug is being lost per unit time

Rate of drug elimination is constant

43
Q

what are some examples of drugs that follows zero-order kinetcs?

A

1) Ethanol
2) Phenytoin (high therapeutic dose)
3) Salicylates (high therapeutic dose)

44
Q

What is meant by clearance?

A

and estimate for the amount of drug cleared from the body per unit of time

Cl = Ke (0.693 * Vd) / T (1/2) or Infuision rate (in) / Css

The higher the Vd the higher the clearance

45
Q

What are the organs responsible for clearance?

A

1) Kidney (Urine)
2) Liver (bile)

46
Q

What are the organs responsible for excretion?

A

1) Kidney (urine
2) liver (bile)
3) gut wall - gut lumen - feaces
4) breat milk
5) sweat

47
Q

describe the biliary excretion

A

1) active transport
2) saturable, inducible, inhibitable
3) MW 300-500

48
Q

What is the enterohepatic circulation?

A

the process of drug elimination from the liver to the bile duct and then to the small intestine, where the drug might face deconjugation and be absorbed again due to the presence of bacteria

49
Q

how could you eliminate acidic and basic drugs in case of suicide respectively?

A

1) weak acids can be eliminated by NaHCO3 (Alkalizing agent)
2) weak bases can be eliminated by NH4Cl (Acidifying agent)

50
Q

What is meant by maintenance dose?

A

a dose of drug enough to replace what was eliminated, changed in renal failure patients,

Dose rate = elimination rate (clearance)

Dose rate (IV)= drug plasma average concentration Css * Cl

dose rate(oral) = Target dose/bioavailibility,

51
Q

when do we give a loading dose?

A

when the Css is very high due to high half-life of the drug, reaching steady-state concentration faster

52
Q

How to calculate the loading dose?

A

Loading dose (IV) = Target concentration * Vd

Loading dose (ORAL) = target conc * Vd / F (Bioavailibility)

53
Q

How to calculate the steady-state concentration?

A

4-5 half lives

54
Q

General key points

A

Volume Distribution = Amount injected / [Css steady state]
Clearance = 0.693 * Vd / t1/2
4-5 half-lives to get to a steady state
Maintenance dose = [Css Steady State] * CL / F
Loading dose = [Css Steady State] * Vd / F

55
Q

what is the main mechanism drugs work with?

A

Receptor mediated

56
Q

what characterizes the interaction between the drug and the receptor?

A

1) Affinity
2) Intrinsic activity (ability to produce a response)

57
Q

What is meant by efficacy?

A

it is the capacity of a drug to produce a maximal response (Emax) at full receptor occupancy

58
Q

what is meant by potency?

A

the different doses of two drugs needed to produce the same response

Drug A is 10x more potent than B, when 5mg of A is required to produce the same effect of 50mg of drug B

59
Q

What are the different types of drug response?

A

1) Graded
2) Quantal

60
Q

What is an example of graded response?

A

like BP we can measure the graded effect of drugs given with different doses

61
Q

What is meant by quantal effect?

A

it is whether a drug produces a therapeutic effect or not, can be measure by the percentage of patients responding to it

62
Q

What is meant by E50?

A

the concentration of drug required to reach half of the effect

63
Q

What is meant by effective concentration/dose 50 EC50/ED50?

A

Plasma drug concentration (EC50)/ dose (ED50) of the drug which produces the effect in 50% of subjects

64
Q

what is the meaning of Lethal Conc/Dose 50%

A

Plasma drug concentration or dose of the drug that induces death in 50% of experimental samples/subjects

65
Q

What is the meaning of MLC?

A

Minimum lethal concentration will lead to death

66
Q

What is the meaning of TD50?

A

50% of the toxic dose

67
Q

what ais the factor considered when talking about potency?

A

the lower the effective dose/concentration the higher the potency

68
Q

what factor is considered in the description of the efficacy of a drug?

A

the higher the Emax (more effect) the more the efficacy

69
Q

what are the four types of receptors?

A
  1. Ligand-gated ion channels (inotropic receptors)
  2. G-protein coupled receptors (metabotropic receptors)
  3. Enzymatic receptors (tyrosine kinase)
  4. Nuclear receptors (transcription factors)
70
Q

What is the classification of drugs?

A

1) Agonist
2) Antagonist
3) Partial agonist
4) Inverse agonist

71
Q

Example of an agonist drug and how it works

A

Methacholine (Cholinomimetic drug), which has both high affinity and intrinsic activity triggering the maximal biological response, mimicking the effect of acetylcholine on cholinergic receptors

they are specific to one receptor

72
Q

what is an antagonist drug?

A

drugs that bind to receptors with high affinity possessing zero intrinsic activity, it has no effects in the absence of an agonist but decrease its activity when present

73
Q

what are the types of antagonists?

A

1) Chemical antagonism (the binding of a drug to another making it inactive, like the binding of Protamine “+ charged” to Heparin “- charged” making it inactive

2) Physiological /Functional antagonism “opposite in function” (they have an opposite physiological function of different receptors like histamine (Bronchoconstrictor) and epinephrine (Bronchodilator))

3) Pharmacokinetic antagonism, (a drug that affects the absorption, Distribution, metabolism, & elimination of another drug, like the increased metabolism (and decreased bioavailability) of warfarin in the presence of phenobarbitol as it stimulates the liver enzymes)

4) Pharmacological antagonism (Binds to receptors blocking the agonist activity)
- Competitive ( Reversible, blocks the agonist ability to bind) we can overcome its effect by increasing the agonist concentration (Atropine is a competitive inhibitor to Ach)
- Non-competitive (Irreversible, binds to another site of the receptor blocking the action of the agonist)

74
Q

what is a partial agonist drug? and how does it work?

A

They have a full affinity to the receptor but low intrinsic activity (they do not reach their maximum effect), like aspirin, pindolol, and pentazocine

75
Q

what is an inverse agonist drug and how does it work?

A

they have full affinity towards a receptor with an opposite intrinsic activity like ß-Carboline is inverse agonist for Benzodiazepines receptors

they reduce the activity of an organ

The difference between inverse agonist and antagonist is in their mechanism of action while inverse agonist does it by intrinsic activity and the antagonist does it by blocking the receptor from the drug stimulating it

76
Q

what is meant by the therapeutic index?

A

it is a measurement of drug safety

77
Q

what is the equation to calculate the therapeutic index?

A

TI = LD50/ED50

The higher the TI the safer the drug as it means that the higher the dose to become lethal the safer the drug

TI should be greater than 1

In a graph it is between the ED50 (MinimumEffectiveDose) AND TD50

78
Q

what are some examples of drugs that have a low TI?

A

Warfarin
Digoxin
Lithium
Theophylline

79
Q

how are receptors regulated?

A

1) Sensitization/Up-regulation
2) Desensitization/Down-Regulation

80
Q

what is sensitization/Up-regulation?

A

It is the increase in density (Number) of receptors due to either:

1) Prolonged usage of a blocker
2) Inhibition of the release/synthesis of the hormone/neurotransmitter

  • It increases the response with a smaller amount of the drug shifting the graph towards the left
81
Q

what is desensitization/Down-Regulation?

A

A decrease in the number of receptors due to:

1) Prolonged use of agonist
2) Inhibiting the degradation of agonist

Causes tolerance (Increasing the amount of drug to obtain the same effect)

82
Q

what is meant by tachyphylaxis?

A

Acute tolerance is the decrease of tissue sensitivity after a short-term exposure

83
Q

What is tolerance?

A

the body’s physical adaptation to a drug requiring more amounts of the drug over time to get the initial effect as the number of receptors decreases.

  • it shifts the graph towards the right

Pharmacology/LC (2 decks)

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