MP321 week 3 Flashcards
HIV viral replication steps
1- fusion of HIV to the host cell surface
2- HIV RNA reverse transcriptase , integrase and other viral proteins enter the host cell
3- viral DNA is formed by reverse transcription
4- viral DNA is transported across the nucleus and integrates into the host DNA
5- new viral RNA is used as genomic RNA and to make viral proteins
6- new viral RNA and proteins move to the cell surface and a new, immature, HIV forms
7- the virus matures by protease releasing individual HIV proteins
key HIV enzymes
protease
reverse transcriptase
integrase
inhibit these and stop HIV (viral) replication
define NRTIs
nucleoside reverse transcriptase inhibitors
how do NRTIs work
mimic the natural nucleosides that are incorporated into the double helix chain formation of DNA-RNA and DNA
NRTI prodrug and activated only viral kinase
target polymerase during transcription
prodrugs metabolised to give non-functional nucleosides
when NRTIs are incorporated into growing chain it causes chain termination
no more HIV can be made and CD4 cells not further compromised
to incorporate the nucleoside into the chain it needs to be converted to a nucleotide
the hydroxyl group enables the molecule to be seen and incorporated into the chain, the changes from hydroxyl to N3 in structure leads to chain termination
define prodrug
a biologically inactive compound which can be metabolized in the body to produce a drug
what is remdesivir used to treat
acute, severe covid-19, works differently to other NRTIs
chemistry of remdesivir
3’ hydroxyl group present - so a nonobligate chain terminator
although theoretically may bond to another nucleoside, it does not
note how others have this functional group removed to be active
it still works because it has a bulky group which hides and blocks the hydroxyl group
adenosine like most involved in base pairing with uracil
as this is very similar to how adenosine makes base pairs, this possibly is why it gets incorporated by viral polymerase - enables transcriptase to see and recognise
as it has a carbon - carbon bond it is more stable against nucleases as not a semi-aminal bond
define NNRTIs
non-nucleoside reverse transcriptase inhibitors
NNRTIs
Non-nucleoside reverse transcriptase inhibitors
Known as allosteric inhibitors (holy grail of inhibitor type)
Bind to a lipophilic pocket at the base of the “thumb” area of the RT enzyme
Conformationally prevents the enzyme from allowing the single strand of RNA to be transcribed
Prevents replication and protects CD4 cells
useful as they don’t block natural active site
targets polymerase during transcription as allosteric inhibitors
protease inhibitors (PI)
large proteins made following transcription and translation
proteases are inhibited by other small molecules
processed into smaller proteins to make virion
protease cleaves the larger proteins
hydrolysis of the protein peptide bond
HIV protease is a much smaller enzyme than the equivalent host aspartate proteases
Cleaves substrates N-terminal to proline residues unlike mammalian proteases (selectivity)
Tyr-Pro was identified as a cleavage site for the HIV protease
Rationale for inhibitor design was based on Phe-Pro or Tyr-Pro motif
mimic substrate with non hydrolysable functionality
hydrolysis of amide bond
split into amine and carboxylic acid and get rid of water
how does saquinavir work
when it is in the active site it won’t get cleaved and prevents the natural substrate binding, need to make the drug more favourable to get into site first
name 5 properties an ideal anti-microbial formulation should be
- effective against targeted infection
- able to reach (specifically) site of action
- rapid onset
- controllable duration
- free of side effects
name 2 things that will influence the route of administration and dosage form for antimicrobials
- site of infection
-severity of infection
topical administration- used for ?
mild infection
IV/IM administration- used for?
severe infections
name one advantage of topical administration onto the skin
local action- drug retained in the skin
to be suitable for topical drug delivery the drug should be (3)
- low MW (less than 500 Da)
- moderately lipophilic (log P between 1 and 4)
- effective at low dose (less than 10mg/day)
name the three formulation types for skin
- liquid
- semi-solid
- solid
name the 2 principles of formulation for the skin
- formulation should be stable but allowing drug to be released after application
- vehicle should allow some solubility of the drug but should not retain the drug by being a very good solvent
name one advantage and 2 disadvantages of a liquid formulation for the skin
ad- rapid short term input of permeant into the skin
dis- low drug delivery
dis- treatment of surface infection only
name 2 advantages and one disadvantage of ointments
ad- increase of transdermal drug flux (the number of molecules moving through a given cross- sectional area during a given period of time)
ad- prolonged drug delivery
dis- messy to use due to greasy nature
name 2 advantages and one disadvantage of creams
ad- easier to apply than ointments
ad- can be washed off skin surface
dis- less occlusive than ointments, therefore less beneficial in dry skin conditions
name an example of a solid formulation for skin application
spray powder
name one of the challenges with topical application to the nail
nail has a hard keratinised structure- need keratolytic components to increase diffusion of drug through nail plate
name one important must have property of topical formulae for the eyes
formulation must be sterile
one average what is the range (%) of drug in topical formulations that reaches the aqueous humour in the eye
1-5%
name 2 advantages and one disadvantage of eye drops
ad- easy to administer
ad- homogenous (better dose uniformity)
dis- rapidly drained out of the eye (90% in first 30s)
name 3 advantages and 3 disadvantages of eye ointment formulations
ad- reduced drug drainage caused by tear flow
ad- sustained drug release (2-4h)
ad- incorporation of drugs with poor aqueous solubility
dis- more difficult to administer than drops
dis- more variation in dosing
dis- blurs the vision
name 2 advantages of ear drop formulations
ad- easy to administer
ad- dose uniformity
name 2 considerations for topical applications for the nose
-need of increasing nasal residence time (bioadhesion, increased formulation viscosity
-mucocilliary clearance
define mucocilliary clearance
removal of the drug from the nasal cavity
name 4 oropharyngeal formulations
-solutions
-gels
-suspensions
-mucoadhesive buccal tablets
name 4 vaginal formulations
gels
creams
pessaries
ovules
define pessary
vaginal suppository- solid, single-dose formulations of ovoid shape
define ovules
vaginal capsules, shell pessaries- solid, single dose formulations similar to oral soft capsules but shape is often elongated and larger
name 2 advantages and 1 disadvatange of topical formulations for the vagina
ad- treatment of local infections with a much lower dose than with oral administration
ad- no need of absorption of the drugs for local action
dis- release of the drugs influenced by varying volumes of vaginal fluid
oral administration types (2)
solid
liquid
parenteral administration types (2)
injections and infusions
liposomes
name one advantage and one disadvantage of oral administration (general)
ad- the simplest, most convenient and safest means of drug administration
dis- possibility of irregular absorption of certain drugs
name 4 advantages and 2 disadvantages of tablet formualtions
ad- accurate dosing
ad-convenient to handle and carry
ad- easy to take
ad- controlled release of the drug
dis- poor bioavailability of some drugs
dis- local irritant effects to GI mucosa
name 3 advantages and 3 disadvantages of capsule formulations
ad- accurate dosing
ad- drug release faster than tablets
ad- shell masks taste of unpleasant drugs
dis- bulky materials can result in a large capsule
dis- susceptible to moisture
dis- not suitable for drugs that are inactivated in the stomach
name 2 advantages and 2 disadvantages of powder formulations
ad- reconstituted just before use to avoid chemical degredation
ad- fast drug release compared to tablets and capsules
dis- not suitable for drugs that are inactivated in the stomach
dis- less convenient to carry and self-administer
name 2 advantages and 1 disadvantage of suspensions
ad- drug absorption fast than tablets or capsules
ad- convenient when drug is not soluble in water and when non-aqueous solvent cannot be used
dis- risk of sedimentation
can a suspension with caking be redispersed ?
no