pharmacokinetics FOM Flashcards
1
Q
How are enteral formulations administered?
A
- mostly oral but also sublingual and rectal
2
Q
Example of enteral formulation
A
- tablet: compressed. has enteric coating which prevents disintegration until passage through stomach
- extended/sustained/modified release, have permeable coating allowing slow release from osmotic core
3
Q
How are parenteral formulations administered?
A
- straight into vein, skin, muscle
4
Q
Examples of topical formulations
A
- cutaneous: cream, ointment, gel ,paste
- inhaled: MDI, nebuliser
- eye drops, nasal sprays, suppositories, dermal implants
5
Q
What state can drugs cross the lipid membrane?
A
- non-ionised
6
Q
How is non-ionised state achieved by drug?
A
- acid drug in basic environment
- basic drug in acidic environment
7
Q
What is bioavailability?
A
- fraction of administered dose reaching general circulation unchanged
8
Q
How is bioavailable dose worked out?
A
- administered dose x bioavailability
9
Q
What is volume of distribution?
A
- volume of plasma in which the total amount of drug would need to be dissolved to give observed drug conc.in blood or plasma
- relatively fixed characteristic for each drug and is independent of drug dose
- units are litres but is often expressed per body weight to compare individuals
10
Q
What is the main organ involved in metabolism?
A
- liver: catabolises lipophilic drugs typically inactive and water-soluble metabolites
11
Q
Why is the rate of elimination important?
A
- determines the rate of drug administration needed to maintain drug concentration in the body
12
Q
What are the two phases of drug metabolism?
A
- phase 1: inactivation
- phase 2: conjugation
13
Q
What occurs in phase 1 of drug metabolism?
A
- drugs undergo chemical modification by CYP450 enzymes by addition or exposure to functional groups
- purpose is to drug more water-soluble
14
Q
What occurs in phase 2 of drug metabolism?
A
- become chemically linked to larger, more water-soluble molecules
- increases drug’s water solubility for faster elimination from body
15
Q
Describe the first pass effect
A
- when passing through liver, enzymes may metabolise a significant portion of the drug before it reaches the bloodstream
- can reduce bioavailability of certain orally administered drugs
16
Q
What is a prodrug?
A
- drug administered inactive with metabolism needed to activate them
17
Q
Examples of routes excretion
A
- pulmonary, renal, faecal
- glomerular filtration, reabsorption and secretion
18
Q
What are the different pharmacodynamic effects?
A
- additive: overall effect is sum of each effect
- synergistic: overall effect is greater than additive
- antagonistic: overall effect is less than additive some of each drug
19
Q
What are zero-order kinetics?
A
- constant amount of drug is eliminated from body over given amount of time
- regardless of plasma conc.
- fixed amount of drug is metabolised/excreted per unit time
20
Q
What are first-order kinetics?
A
- proportionally increase elimination as plasma conc. increases
- constant fraction % of drug is eliminated per unit time in a particular organ
21
Q
What is clearance?
A
- volume of blood from which all drug is cleared per unit of time in a particular organ
- constant for particular drug and independent of drug dose
22
Q
A
