Additions

Question 1

What are the factors affecting drug absorption?

Answer 1

• Factors related to the drug

- Factors related to the absorbing surface

Question 2

What are the factors related to the drug that affects drug absorption?

Answer 2

 Molecular size: Small molecules are absorbed > large molecules.

 Drug formulations: Sustained-release (SR) tablets→ slow absorption.

 Drug combination: Vit C →↑ iron absorption.

 Lipid solubility: The pKa and drug ionization

Question 3

What are the factors related to the absorbing surface that affect drug absorption?

Answer 3

 Route: The IV route is the fastest, while the rectal is the slowest.

 The integrity of the absorbing surface: may ↑ or ↓ absorption.

 Total surface area: absorption across the intestine more
efficient (intestine has a large surface area).

 Rate of the circulation: at the site of absorption (blood flow).

Question 4

How is loading dose calculated? And what does it depend on?

Answer 4

Ld = Vd * Cp

Vd (volume of distribution)

Question 5

How to calculate maintanence dose? And what does it depend on?

Answer 5

{MD= CL X Cp}

Cl (clearance rate)

Question 6

What is the definition of clearance?

Answer 6

 The volume of fluid (usually plasma or blood) from which drug is removed per
unit time (ml usually per minute).

Question 7

What is the definition of elimination?

Answer 7

 The processes involved in the removal of drugs from the body (and/or plasma)

Question 8

What is elimination half-life? And what is it used for?

Answer 8

• It is the time taken for the concentration of a drug in the blood to fall half its original value.
• Used in determination of inter dosage interval.

Question 9

What are the patterns of elimination?

Answer 9

• First-order elimination

- Zero-order elimination

Question 10

What is the definition of first-order elimination? And what dugs show this type of elimination?

Answer 10

• A constant fraction (PERCENTAGE) of the drug is eliminated per unit time (t1/2 is constant).
• Most drugs follow first order

Question 11

What is the definition of zero-order elimination?

Answer 11

• A constant AMOUNT of drug is eliminated per unit time (t1/2 is variable), Drug cumulation and interactions are common.
• Aspirin & phenytoin (zero-order in high doses)

Question 12

What is steady-state concentration?

Answer 12

• Steady level of drug in the plasma is achieved when the rate of administration equals the rate of elimination.
• Steady-state plasma concentration abbreviated → Cpss.

Question 13

What is the concept of the role of 5?

Answer 13

The rule of 5 :

1. Cpss is reached after 4-5 t 1/2.
2. If a dose is changed, new Cpss after 4-5 t 1/2
3. Complete drug elimination after 4-5 t 1/2. (if the drug given once or stoped after continuous administration)

Question 14

How to achieve Cpss. After first t 1/2?

Answer 14

To achieve Cpss after first t 1/2 → give double the dose (loading dose) in the first time only then give the usual dose (maintenance dose)

Question 15

Percentage of the drug in body after one-time administration or stopping after continuous administration.

Answer 15

50
25
12.5
6.25  
3.125

Question 16

Percentage of the drug in blood in cases of Continous administration

Answer 16

50
75
87.5
93.75 
96.875

Question 17

What are the types of receptors?

Answer 17

Ligand-gated ion channel:
- Nicotinic & GABAA receptor.

G protein-coupled:

• Muscarinic receptors.
• Adrenergic receptors.
• Histamine 1&2 receptors.

Tyrosine kinase linked:
- Insulin receptor.

Intracellular:
- Glucocorticoid receptors.

Question 18

What are adverse drug reactions?

Answer 18

An ADR is any response to a drug which is noxious, unintended and occurs at doses used in man for prophylaxis, or therapy.

Question 19

What are types of clinical defect of the drug?

Answer 19

• Desirable

- Undesirable

Question 20

What are type types of adverse drug reactions?

Answer 20

Type A - Augmented 
Type B - Bizzare
Type C - Continous
Type D - Delayed
Type E - End of use

Question 21

Type A - Augmented

Answer 21

Related to the pharmacological action

E.g: bleeding with anticoagulants

Question 22

Type B - Bizzare

Answer 22

Unrelated to the pharmacological action

example: plastic anemia from carbimazole

Question 23

Type C - Continous

Answer 23

Chronic affects - dose and time related

Example: Analgesic nephropathy

Question 24

Type D - Delayed

Answer 24

Unmmon, time-related delay in Onset

Example: Tetratogenesis

Question 25

Type E - End of use

Answer 25

Soon after withdrawal

Example: MI by beta blocker withdrawal

Question 26

What are examples of type A ADRs?

Answer 26

They may result from an exaggerated response (e.g. hypotension from an antihypertensive) or non- specificity (e.g. anticholinergic effects with antihistaminic).

Question 27

What are predisposing factors for ADRs?

Answer 27

▪ Multiple drug therapy

▪ Age :
o very old
o very young

▪ Associated disease:
o impaired renal function.
o impaired hepatic function.