Pharmacodynamics (DOSE-RESPONSE RELATIONSHIP)

Question 1

Describe the two types of dose-response curves.

Answer 1

The two of dose-response curves the quantitative (graded) dose-response curve and the qualitative (All/None) dose-response curve.

Question 2

Define dose-response relationship.

Answer 2

Dose-response relationship refers to the relationship between the dose of a drug or treatment and the response or effect it produces in an organism.

Question 3

Graded dose response curve is obtained if the degree of response is ………….
EX ?

Answer 3

depicted against log the dose ///
↓ bl. glucose against the dose

Question 3

What parameters can be obtained from Graded dose response curve ?

Answer 3

Efficacy /// Potency (ED50, Slope)

Question 4

Describe what efficacy (Emax) refers to a graded dose-response.

Answer 4

Efficacy (Emax) is the maximal effect produced by a drug, representing the maximum value of the dose-response curve.

Question 5

Describe ED50.

Answer 5

ED50 is the dose that produces 50% of maximal reponse and is used for comparing the potency of different drugs.

Question 5

Define the slope of the middle portion of a dose-response curve in relation to drug potency.

Answer 5

The slope reflects the effect of the drug produced by one unit of the dose. A steeper curve (higher slope) indicates a more potent drug.

Question 6

How is potency assessed in a graded dose-response relation using ED50?

Answer 6

Potency is assessed using ED50, which is the dose that produces 50% of the maximal response. A lower ED50 indicates a more potent drug.

Question 7

Define All/None dose-response relationships.

Answer 7

It refers to the situation where the effect either occurs completely or not at all, typically depicted by a curve showing the percentage of patients responding to a drug against the log dose.

Question 8

Define LD50.

Answer 8

LD50 is the dose that causes mortality in 50% of animals treated with a drug, providing insight into the toxicity level of the substance.

Question 9

What parameters can be obtained from All/None dose response curve ?

Answer 9

ED50 // LD50 // Therapeutic index (TI)

Question 10

Do lower LD50 values indicate higher toxicity?

Answer 10

Yes, a drug with a lower LD50 is considered more toxic compared to a drug with a higher LD50 value.

Question 10

How is LD50 different from ED50?

Answer 10

LD50 is the dose that kills 50% of animals, indicating the toxicity of a drug, while ED50 is the dose that cures 50% of cases, reflecting the potency of a drug.

Question 11

How is Therapeutic Index (TI) calculated?

Answer 11

Therapeutic Index is calculated as the ratio between LD50 (lethal dose) and ED50 (therapeutic dose), where TI = LD50/ED50.

Question 12

Describe the significance of LD50 being much higher than ED50 in drug safety assessment.

Answer 12

If LD50 is significantly higher than ED50, it indicates that the drug is relatively safe for therapeutic use.

Question 12

Describe ED50 in pharmacology.

Answer 12

ED50 the dose that cures 50% of cases and is used for comparing the potency of different drugs.

Question 13

What is the therapeutic window ?

Answer 13

range between the minimum toxic dose and the minimum therapeutic dose.

It is practical for choosing the dose for a patient.

Question 14

what’s a narrow therapeutic window ?

EX : ??

Answer 14

A narrow window betw their effrctive doses & thoses producing adverse toxic effects.

EX: Aminoglycosides, anticoagulants, antiepileptics, hypoglycemic agents, lithium, quinidine, theophylline and tricyclic antidepressants.

Question 15

what are factors modifying Dose-Response Relationship

Answer 15

Age // Sex // Pathological state // Tolerance // Psychological state // Drug Interactions

Question 16

Describe the age method for calculating child dose.

Answer 16

The child dose is calculated by multiplying the adult dose by the child’s age in years, then dividing by the sum of the age and 12.

Question 17

Define the surface area method for calculating child dose.

Answer 17

The child dose is determined by multiplying the adult dose by the child’s surface area in square meters, then dividing by 1.73.

Question 17

How is the child dose calculated using the weight method?

Answer 17

The child dose is calculated by multiplying the adult dose by the child’s weight in kilograms, then dividing by 70.

Question 18

Do you know how the percentage method is used to calculate child dose?

Answer 18

The child dose is calculated as a percentage of the adult dose, with different percentages assigned based on the child’s age.
1 month => 12.5%.
2 months => 15%.
1 year => 25%.
2 years => 33%
7 years => 50%.
12 years => 75%

Question 19

What is the main factor modifying drug action according to the content?

Answer 19

The dose is identified as the primary factor modifying the dose-response relationship in drug action.

Question 20

Describe the impact of certain drugs on female organs in terms of sex hormones and specific examples.

Answer 20

Certain drugs act specifically in the female organs by affecting sex hormones such as estrogen, progesterone, ergot alkaloids, and oxytocin.

Question 21

Explain the potential risks of drug use during pregnancy in relation to teratogenicity and examples of such drugs.Explain the potential risks of drug use during pregnancy in relation to teratogenicity and examples of such drugs.

Answer 21

During pregnancy, some drugs can cause teratogenicity, leading to birth defects. Examples include thalidomide and antithyroid drugs.

Question 22

Define the concept of drug transfer through breast milk in lactating females and provide examples of drugs that can pass to the fetus through milk.

Answer 22

In lactating females, some drugs can pass to the fetus through breast milk. Examples include ephedrine and phenobarbitone.Describe how certain diseases can affect a patient’s to drugs + EX

Question 23

Describe how certain diseases can affect a patient’s to drugs + EX

Answer 23

Certain diseases can make patients more sensitive to specific drugs, leading to adverse reactions or exacerb of symptoms.
EX: bronchial asthma, ß-blockers can trigger an asthmatic attack.
Myasthenia gravis : competetive skeletal Muscles relaxants & quinine => myasthenic attack.

Question 24

Describe pharmacokinetic tolerance.

Answer 24

Phokinetic tolerance is tolerance that occurs due to a significant decrease in drug levels at the site of action, often caused by factors like enzyme induction increasing the liver’s ability to metabolize the drug (epileptic ddrugs as phenytoin & Phenobarbitone).

Question 25

Explain pharmacodynamic tolerance.

Causes & EX

Answer 25

tolerance w/O decrease of drug level.
**Causes **
- decreased sensitivity of receptors => Opiates
- Increase in receptor numbers (up regulation) => B adrenoreceptor blockers.
- Decrease in receptor numbers (down regulation) => B2 agonists.
- increased neurotransmitter release : increase ACH relase by ipratropium.
- counter regulatory mechanisms : salt & water retention by vasodilatros

Question 26

What is tachyphylaxis in the context of tolerance?

Answer 26

Tachyphylaxis refers to acute tolerance where the same effect cannot be achieved even with an increased dose.
EX: tolerance due to the depletion of neurotransmitters like norepinephrine by ephedrine.

Question 27

How does pharmacodynamic tolerance differ from pharmacokinetic tolerance?

Answer 27

Pharmacokinetic tolerance is due to decreased drug levels at the site of action, while pharmacodynamic tolerance occurs without a decrease in drug levels, involving changes in receptor sensitivity, numbers, neurotransmitter release, or counter regulatory mechanisms.

Question 27

Define cross tolerance and provide an example.

Answer 27

Cross tolerance is when tolerance to one drug results in tolerance to related drugs.
EX: the cross tolerance observed between different members of the opioid drug class.

Question 28

Describe the role of psychological factors in patient response to a placebo in medical treatment.

Answer 28

Psychological factors can influence how patients respond to placebos, sometimes eliciting similar effects as the active drug.
Placebos are used in psychological therapy and control studies to distinguish between true drug effects and those influenced by psychological factors.

Question 29

Define the term ‘placebo’ and explain its use in medical research.

Answer 29

A placebo is a substance or treatment with no therapeutic effect, often used in medical research to compare the effects of an active drug against those of psychological factors or other variables.

Question 30

What is meant by drug interaction ?

Answer 30

The response of one drug may be affected by administration of another drug.

Question 31

Types of drug interactions

Answer 31

Antagonsim : decrease reponse by a second drug
EX : βBlockers or α blockers with their agonists.

Enhancment :
Summation : 1 + 1 = 2 : when the effect of two drugs given in combination equals the mathematical summation of their effects when given alone.
EX : paracetamol + codeine→↑analgesia

Synergism : 1 + 1 = 5 : the interaction of two or more drugs when their combined effect is greater than the sum of the effects seen when each drug is given alone.
EX : sulfonamides + trimethoprim (-) two sequential steps in bacterial folic acid metabolism

Potentiation : a + b = B : when one drug does not elicit a response on its own but enhances the response to another drug.
EX : beta lactamase inhibitor (drug a) ↑ antibacterial effect of beta lactamase sensitive penicillin (drug b)