Pharmacokinetics

Question 1

Bioavailability (F)

Answer 1

Will increase if the dissolution is rapid (from drug into free drug starte in blood where its AVAILABLE for use

The amount which reaches the blood UNALTERED by eg liver is bioavailable

Question 2

What is the AUC, and what is it used for

Answer 2

Area under (the) curve measures the total drug exposure, used in measuring Absolute and relative Bioavailability

Question 3

Absolute and relative bioavailebility

Answer 3

Absolute: availibility of drug in blood after non iv admin. iv is 1/100%, used to calculate absolute bioavailability. so when calculating compare it to how much IV is used as it will give 100%

Relative bioavailability: we compaire the bioavailability of one drug to another instead of one drug admin to iv admin

Question 4

first-pass effect

Answer 4

Conc of drug may be greatly reduced before it reaches the bloodstream

Affects the bioavailebility - dose may need to be adjusted

Question 5

Rate of distribution and blood flow

Answer 5

Different blood flow to different organs

1 brain, liver, kidney 2 muscle, skin
3` fat, bone

Question 6

Vd - the distribution of a drug in the blood

Answer 6

Drugs that distribute extensively have relatively large Vd values, and vice versa.

• A very low Vd value may indicate extensive plasma protein binding of the drug.
• A very high value may indicate that the drug is extensively bound to tissue sites.

Question 7

Pharmacologically inert metabolites

Answer 7

metabolism deactivates administered dose of parent drug and reduces effects on body

Question 8

pro-drugs

Answer 8

an ex of Metabolites that may also be pharmacologically active, even more than the parent drug

Question 9

Bioteansformation of xenobiotics

Answer 9

o Oxidizes the xenobiotic (phase I)
o Conjugates water-soluble groups onto the molecule (phase II).

Mainly done in the liver by redox enzymes, termed cytochrome P450 enzymes

Question 10

Biotransformations on general

Answer 10

Phase I: no conjugations, can be active or inactive, functional gr is prod by a reaction. CYP-450!!

Phase II: conjugation resulting in lost activity. Functional gr is used to conjugate.

Question 11

Enzymes inducible by drugs in cell

Answer 11

Only those enzymes located in the endoplasmic reticulum are inducible by drugs. Means that the only subcellular location for enzymatic activity of drugs is in the ER.

Enzymes are induced by drugs, hormones etc so they metabolise drugs

Question 12

metabolic tolerance

Answer 12

A drug may induce its own metabolism

Question 13

Glucuronyl transferase, where, what does it do?

Answer 13

• set of enzymes, involved in phase II reactions. - catalyzes conjugation of glucuronic acid to variety of active centers -OH, -COOH, -SH, and -NH2

In ER

Question 14

Incomplete excretion

Answer 14

accumulation of foreign substances adversely affecting the normal metabolism.

Question 15

Major site of excretion

Answer 15

Kidneys

Question 16

Net renal excretion of drugs

Answer 16

• the amount of drug filtered at the glomerulus
• PLUS the amount of drug secreted by active transport mechanisms in the kidney, - MINUS the amount of drug passively reabsorbed throughout the tubule.

Question 17

Zero-order elimination/kinetics

Answer 17

LINEAR
a constant amount of drug will be eliminated per unit time when we have taken in more drugs than the bodys` elimination mechanism has reached its limit.

Question 18

First-order elimination

Answer 18

• Occurs when drug level is BELOW saturation point
• this is the elimination of most drugs!
• linear function of PLASMA levels!

Question 19

One-compartment open model

Answer 19

• in central tissues
• even drug distr among tissues
• continous loss/elimination after a single administration

Question 20

two-compartment model

Answer 20

• drug elimination in peripheral tissues
• slower!
• more common that one compartment
• has a distr phase where equilibrium is made btw peripheral and central(plasma) tissues - rapid decr, then the decr in plasma cons is more linear - only elimination phase used for calc of Vd, halftime

Question 22

Bio exponential curve

Answer 22

Shows decr of drug level in time (plasma)

Question 23

When can Repeat administration

Answer 23

of drug eliminated by first-order kinetics

Question 24

Steady state

Answer 24

• Re admin of drugs to maintain a steady state.
• Often is better than larger and fewer doses.
• Approx 4-5 halftimes is needed to make a steady state.
• Its independant of the dose size, a steady state will be made either way.

Question 25

Loading dose

Answer 25

needed when therapeutic concentration of drug in plasma must be achieved rapidly (e.g., a life-threatening situation) then the drus is administered at maintenance dose rate to
maintain drug concentration at the desired steady-state level.

Question 26

How is mantinance dose rate calculated

Answer 26

Desired concCLmin*hours

Question 27

Factors influencing drug action, that developes after repeated admin

Answer 27

Tolerance, dependance and allergy

Question 28

Factors influencing drug action, that developes ok the first admin

Answer 28

Idiosyncrasy

= Individual hypersensitiveness, serious symptoms, hereditary

Question 29

Types pf medication creating an allergic response

Answer 29

antibiotics, hormones, anticonvulsants, NSAIDs

Question 30

Factors maintaining drug allergy

Answer 30

contamination of skin, inhalation –

contamination of airways, depot preparations, chronic diseases, atopy

Question 31

Type I allergic reactions typical diseases

Answer 31

PQ Urticaria (hives), oedema, Rhinitis, asthmatic
seizure

Histamine, prostaglandins, leukotrienes, Vasodilatation,, inflammation, Diarrhoea,), atopic dermatitis, in sever cases anaphylactic shock,

Elimination of clinical signs is rapid

Question 32

Elimination Half-life (T1/2) :

Answer 32

• time it takes for the plasma drug concentration to be reduced by 50%.
• applies only to drugs eliminated by first-order kinetics.
• so not if dose excedes elimination capasity! = saturated, zero order