Introduction & Pharmacokinetics

Question 1

Abbreviations

o. d.
b. d.
t. d.s
q. d.s
p. r.n

Answer 1

• o.d. Once daily
• b.d. Twice daily
• t.d.s Thrice daily
• q.d.s Four times daily
• p.r.n. As required

Question 2

Lidocaine is used as a…

Answer 2

Antiarrhytmic drug

Question 3

Time required for one arm-brain cycle

Answer 3

ca. 10 seconds

Question 4

Phenytoin is used to manage…

Answer 4

Status epilepticus

Question 5

Advantages of IV

Answer 5

• Rapid effects
• Absorption circumvented, i.e. not subject to bioavailabilty
• Permits titration of dosage
• Emergency use

Question 6

Cons in use of IV route

Answer 6

• Increased risk of adverse effects
• Risk of embolism
• Not suitable for oily solutions or insoluble substances
• Requires IV access

Question 7

Advantages of subcutaneous administration

Answer 7

• Slow sustained release from repository preparations
• Suitable for some insoluble suspensions

Question 8

Cons of subcutaneous administration

Answer 8

• Not suitable for large volumes
• Somewhat incomplete bioavailability, varies from drug

Question 9

Pros of intramuscular administration

Answer 9

• Slow sustained release from repository preparations
• Suitable for oily vehicles and some irritating substances

Question 10

Cons of intramuscular administration

Answer 10

• Painful
• Less predictable absorption
• Danger from injection at incorrect site e.g. nerve damage

Question 11

Pros of oral route

Answer 11

• Convenient
• Cheap

Question 12

Cons of oral route

Answer 12

• Subject to 1^st pass metabolism
  
  • Propanolol, morphine, statins
• Varying bioavailability
• Effected by food in stomach

Question 13

ADME

Answer 13

Absorption

Distribution; some drugs redistribute or pile up in certain areas e.g. brain

Metabolism; liver/kidney

Exrection

Question 14

Drugs subject to first pass metabolism

Answer 14

Propanolol, morphine, statins

Question 15

Describe first pass metabolism

Answer 15

• The first pass effect (also known as first-pass metabolism or presystemic metabolism) is a phenomenon of drug metabolism whereby the concentration of a drug is greatly reduced before it reaches the systemic circulation. It is the fraction of drug lost during the process of absorption which is generally related to the liver and gut wall. Notable drugs that experience a significant first-pass effect are imipramine, morphine, propranolol

Question 16

Define zero-order eliminatin kinetics

Answer 16

“Elimination of a constant quantity per time unit of the drug quantity present in the organism.”

Question 17

Define First order elimination kinetics

Answer 17

“Elimination of a constant fraction per time unit of the drug quantity present in the organism. The elimination is proportional to the drug concentration.”

Question 18

Define bioavailability

Answer 18

the proportion of a drug or other substance which enters the circulation when introduced into the body and so is able to have an active effect.

Question 19

Formula for working out Bioavailability

Answer 19

F=AUC_oral/AUC_iv

Question 20

Aminophyline/Theophylline Salt factor

Answer 20

Aminophylline is 80% Theophylline

Question 21

Define Volume of Distribution

Answer 21

The apparent volume in which a drug is distributed. Drugs with low V_d are predominantly in the circulation, while drugs with a high V_d are predominantly have diffused into the peripheral tissue compartment

Question 22

Volume of Distribution formula

Answer 22

Question 23

Define clearance

Answer 23

Volume of plasma cleared of the drug per unit time

Question 24

Formula for clearance

Answer 24

Question 25

Half-time formula

Answer 25

Question 26

Define steady state

Answer 26

Drug administered = Drug eliminated

Takes approximately 5 half-lives to achieve C_ss

Question 27

Define maintenance dose

Answer 27

Once Css achieved maintenance dose = amount removed

Question 28

Oral regimen formula

Answer 28

Question 29

loading dose formula

Answer 29

Question 30

Maintenance dose formula

Answer 30