ophthalmic drugs: anti-infective drugs Flashcards
what are the 3 different therapeutic classes of anti-infective drugs
- Antibacterials Topical Oral - Antivirals - Anti-protozoals
what 2 forms is antibacterial drugs available in
- Topical
- Oral
even though anti infective drugs have a long shelf life, why do optometrists not stock them in practice
because they won’t use them enough for us to have a stock of them and some of them need to be refrigerated so its a hassle
how much % do anti infective drugs count for as prescription ophthalmic drugs in the UK
17%
why is 17% an under estimation of anti infective drugs supplied in the UK
because that counts for prescription only, and many anti infective drugs are available OTC or pharmacists can supply chloramphenicol
when will a pharmacist decide to supply a px with chloramphenicol
only if the px is suspected of having acute bacterial conjunctivitis (and not for anything else)
what can an optometrist supply chloramphenicol to a px for that a pharmacist can’t and how
as a POM drug which has a broader licence to treat post corneal abrasion
the optom will use a signed order where they write down the drug name and give it to the pharmacist
what do drugs exploit
the difference between human (eukaryotic) and bacterial (prokaryotic) cells
list 4 differences between bacterial cells and human cells
- Bacterial cells have a unique cell wall
- There are differences in their cell membrane
- Bacterial cells show differences in the mechanism of DNA and protein synthesis
- Bacterial cells have different biosynthetic pathways
what do the differences between human and bacterial cells form the basis for
the selective toxicity of anti-bacterial drugs
what are drugs that kill the cell called
bactericidal
what do bacteriostatic drugs do
inhibit growth of the bacteria
name 2 drugs which affect the cell wall synthesis
- Penicillins
- Cephalosporins
name 2 drugs affecting the bacterial cell membrane
- Polymyxin B
- Propamidine
name 4 drugs affecting bacterial protein synthesis
- Aminoglycosides
- Tetracyclines
- Chloramphenicol
- Fusidic acid
name a drug affecting bacterial DNA synthesis
Fluoroquinolones
name a drug affecting bacterial metabolism
Sulphonamides
what is the most common way that a anti bacterial drug works
affecting bacterial DNA synthesis
name 5 general considerations when selecting a antibiotic
- Spectrum of cover e.g.
Narrow vs broad
Single vs combination - Penetration into appropriate tissue
- Mode of action
- Route of administration
- Side effects e.g.
Tolerability
Pregnancy / Lactation
what 2 variations come under spectrum of cover when choosing an antibiotic
Narrow vs broad
or
Single vs combination
what 2 examples of side effects need to be considered when choosing an antibiotic
- Tolerability
- Pregnancy / Lactation
what 2 examples of penetration into appropriate tissue needs to be considered when choosing an ophthalmic antibiotic
- topical
or - injected into eye
give 4 examples of routes of administrations of anti bionics
- topical
- orally
- injection
- slow release implant
what is the name of the test to check the sensitivity of antibiotics
Kirby-Bauer Antibiotic Sensitivity test
when can the Kirby-Bauer Antibiotic Sensitivity test be carried out on a bacteria
once its isolated
list the steps of how the Kirby-Bauer Antibiotic Sensitivity test is carried out
- a colony of bacteria is picked off the agar plate
- emulsified in a small volume of saline and then spread on a sensitivity test agar plate
- a paper disc, which has been impregnated with various antibiotics, is placed on top of the culture
- which is then incubated at 37C for 18 hours
- zones of diameter are read around each antibiotic disc and compared with standard values to judge whether the zone size represents a sensitive, intermediate or resistant isolate
which condition is the Kirby-Bauer Antibiotic Sensitivity test the gold standard treatment for
bacterial keratitis
you take a biopsy of the ulcer to sample the bug that is growing
list the 3 antibiotics available to all registered optometrists
- Chloramphenicol
- Fusidic acid
- Propamidine (P medicine bought OTC)
what is the antibiotic Polymyxin B available to optometrists as
Additional supply (by those who took additional qualifications)
what type of antibiotics are available to independent prescribing optometrists
All anti-infectives available for the treatment of diseases of the eye and surrounding tissues
(only restriction is injections)
what type of antibiotics is chloramphenicol
- broad spectrum
- Bacteriostatic (may be bacteriocidal for some species at high concentration)
- resistance if fairly low
what is chloramphenicol not affective against
pseudomonas
what condition is linked with systemic use of chloramphenicol but very unlikely with topical chloramphenicol
aplastic anaemia and ‘Grey Baby Syndrome’
what is aplastic anaemia
a life threatening stem cell deficiency which will need a bone marrow transplant
what is grey baby syndrome
a condition which can occur if chloramphenicol is given intravenously to babies in high doses
what is the UKs first choice of drug for most ocular surface infections
topical chloramphenicol
what is chloramphenicol officially licensed for and give 3 examples
the treatment of superficial infections of the eye
e. g.
- bacterial conjunctivitis
- infective blepharitis
- prophylaxis following trauma
what is prophylaxis
a treatment of antibiotic given to px in order to avoid them getting a bacterial infection
what are the 2 different formulations and concentrations of POM chloramphenicol available in
what else are POM chloramphenicol available in addition to this
- Redidrops, 0.5% POM
- Chloromycetin Ophthalmic ointment, 1% POM
- unit dose (minims)
how often should POM chloramphenicol be used
1-2 drops every 3-6 hours for 1 week
what happened to chloramphenicol eyedrops in 2005
it was reclassified from POM to P for the treatment of acute bacterial conjunctivitis
when was chloramphenicol ointment reclassified from POM to P
2007
what is the mode of action of chloramphenicol
The binding of chloramphenicol to peptidyl transferase on the 50S ribosomal subunit prevents the incorporation of new amino acids to the growing peptide chain
it works by inhibiting bacterial synthesis, the ribosomes goes along the messenger RNA and you have a growing peptide chain thats standard in all cells. The ribosomes used in bacteria are different to ribosomes used in human cells, so chloramphenicol binds to bacterial ribosomes and inhibits the growth of that peptide chain
list the 5 isolates associated with bacterial conjunctivitis
- Stapha = Staph. aureus
- Staphe = Staph epidermis
- Haemop = Haemophilus species
- Pseudo = Pseudomonas
- Strep = Streptococcus species
what are the 2 bugs that are most common in bacterial conjunctivitis
- Stapha = Staph. aureus
- Staphe = Staph epidermis
which bug is rarely a cause of bacterial conjunctivitis
Pseudo = Pseudomonas
which bug is the next most common after staph to cause bacterial conjunctivitis
Strep = Streptococcus species
which bug is the most likely to cause bacterial conjunctivitis in children than in adults
Haemop = Haemophilus species
what did a randomised double blinded treatment of chloramphenicol in the treatment of bacterial conjunctivitis show
that people just get better without any treatment and shows no statistical difference between chloramphenicol and the placebo, so if you do nothing it is just as affective
what is the POM Fusidic acid effective against
a broad range of gram +ve organisms (particularly Staph. Aureus)
what type of antibiotic is fusidic acid
Bacteriostatic (may be bacteriocidal at high concentrations)
what is the antibiotic fusidic acid licensed for
for the treatment of bacterial conjunctivitis
why will fusidic acid be used instead of chloramphenicol
because you only need to put it in twice a day instead of 4x a day
is easy to use on children
give a reason where fusidic acid is not an appropriate agent for acute bacterial conjunctivitis in children
because it is ineffective against Gram-negative H influenzae, the most common causative pathogen in this population
name 2 off licence uses of fusidic acid
- prophylaxis following corneal abrasion
- blepharitis
what is the trade name of the only formulation of ophthalmic fusidic acid available
Fucithalmic, POM
what does it mean when a drug isn’t licensed for that purpose but it still used
the drug company never ran clinical trials on these patients
how often should Fucithalmic, POM be applied
twice daily application
what form does fusidic acid come in and what advantage does this have
comes as a gel
so stays on the ocular surface much longer than eye drops
what makes fusidic acid a good ocular surface agent
it doesn’t penetrate the ocular tissues and does not get as far as the aqueous
which bacterial bug does fusidic acid have good efficacy against
staphylococcus
what is the age group for chloramphenicol POM
> 1 month old
what is the age group for chloramphenicol P
> 2 years old
what is the instructed dose intake of chloramphenicol
- Put one drop into the affected eye(s) every 2 hours for 2 days, and then three times a day for 5 days.
- Ointment at bedtime
what is the age group of Fusidic acid 1% eye drops
Fucithalmic (POM)
> 1 month
what is the instructed dose intake of Fusidic acid 1% eye drops Fucithalmic (POM)
1 drop 2x per day for 7 days
why is the age group of the OTC/P chloramphenicol > 2 years old
because of the theoretical risk of grey baby syndrome
which drug was discontinued in October 2012 and what properties did it have
- POM Polymyxin B
- where chloramphenicol was not good against game -ve bugs, this drug was
- it attaches to and interferes with the functioning of the cell membrane of aerobic Gram-negative bacteria, and bacitracin inhibits the synthesis of the cell wall of Gram-positive bacteria.
which bacterial bug was the POM Polymyxin B active against
P aeruginosa
which drug is active against gram +ve bacteria but less active against gram -ve bacteria, and also has anti fungal and anti amoebic properties
what treatment is it used for
OTC Propamidine
used topically for the treatment of minor eye infections such as conjunctivitis and blepharitis
it is an Aromatic diamidine disinfectant
OTC Propamidine is not an antibiotic, but is an
Aromatic diamidine disinfectant
how does OTC Propamidine work
by acting on the bacterial cell membrane, it increases it’s cell permeability and is bacteriostatic
what is OTC Propamidine used by ophthalmologists for
patients who come into A&E with acanthamoeba keratitis
what are the 2 different formulations of (P) propamidine available
- Brolene
- Golden eye ointment
what is (P) propamidine licensed for
treatment of superficial infections of the eye
e.g. bacterial conjunctivitis and infective blepharitis
what is the instructed dose intake of (P) propamidine
1-2 drops up to 4x daily
what did pharmacists used prior to chloramphenicol as an anti-infective agent
(P) propamidine
list 4 other anti-bacterials that are used in ophthalmology
- Quinolones
- Aminoglycosides
- Tetracylines
- Azithromycin
how does the ophthalmological anti bacterial Quinolones work
Inhibit DNA gyrate
they’re broad spectrum drugs
list 4 examples of Quinolones
- Ofloxacin
- Ciprofloxacin
- Levofloxacin
- Moxifloxacin
name the 2 newer generation Quinolones anti bacterials and why are there newer generation ones out
- Levofloxacin
and - Moxifloxacin
newer ones are added all the time because the old ones become useless as so many bacteria become resistant to them, therefore companies have to develop new ones to stay one step ahead of the bacteria
how does the ophthalmological anti bacterial Aminoglycosides work
Inhibits protein synthesis
is bactericidal
they’re broad spectrum drugs
what is a disadvantage of the ophthalmological anti bacterial Aminoglycosides
they are toxic to the ocular surface especially thick corneas
name 2 examples of the ophthalmological anti bacterial Aminoglycosides
- Gentamicin
- Tobramycin
how does the ophthalmological anti bacterial drug Tetracylines work
Inhibit bacteria protein synthesis by blocking the attachment of the transfer RNA-amino acid to the ribosome
they’re broad spectrum drugs
what is the ophthalmological anti bacterial drug Tetracylines used to treat
lid margin disease
name 2 examples of the ophthalmological anti bacterial drug Tetracylines
- Doxycycline
- Minocycline
how is the ophthalmological anti bacterial drug Tetracylines administered
orally
instead of topically
what 2 things is the ophthalmological anti bacterial drug Azithromycin licensed for
- trachomatous conjunctivitis caused by Chlamydia trachoma’s
- acute bacterial conjunctivitis
what is the off license use for the ophthalmological anti bacterial drug Azithromycin
to treat blepharitis
what are viruses and how do they work
- intracellular parasites
- they need to take over cells in order to divert that cells machinery for producing proteins and DNA into synthesising and assembling new viruses
- so an single virus infects and then sheds multiple viruses which go on to infect other cells = how the virus propagates
what is the most common virus of the eye and what does it cause
- herpes simplex HSV
- same virus that causes the chickenpox can be reactivated and cause cold sores and herpes simplex keratitis
why is the herpes simplex HSV a problem
because following primary infection e.g. chicken pox, you don’t completely eradicate the virus and it tends to become latent where it travels down the sensory nerves and sits within the trigeminal ganglion, to be subsequently reactivated
which type of patients are most likely to re-contract the herpes simplex virus HSV
the immunocompromised e.g HIV +ve or on steroids
what type of virus are herpes virus
DNA viruses
name 3 examples of the herpes virus
- Herpes Simplex
- Varicella zoster
- Cytomegalovirus
name 3 properties of HSV
- Primary
- Recurrent
- Congenital
which type of HSV is most common
HSV-1
what do 60% of children have and by when
HSV by 5 years
which type of HSV is most congenital
HSV-1
80%
what ocular signs are recurrent in HSV
- Thin dendritic ulcers
- Contain live virus
what ocular signs is found with Varicella zoster VSV
Ophthalmic shingles
how many Varicella zoster VSV patients with periocular shingles have eye involvement
50-72%
which type of patients can the Cytomegalovirus CMV infections occur in
immunocompromised individuals e.g. AIDS, post-transplant
what does the Cytomegalovirus CMV present as in the eye
a viral necrotizing retinitis
which is sight threatening
which herpes virus infects the back of the eye rather than the front
Cytomegalovirus CMV
which antiviral drug treats herpes simplex keratitis
aciclovir
how does the drug acyclovir which treats herpes simplex keratitis work and what is the mechanism for this
by inhibiting viral DNA synthesis
-Aciclovir enters the cell and is
converted to aciclovir monophosphate by the herpes simplex virus enzyme thymidine kinase (TK).
- Enzymes add two more phosphates to form the active drug aciclovir triphosphate.
- The aciclovir triphosphate competes with 2- deoxyguanosine triphosphate (dGTP) as a substrate for viral DNA polymerase.
in other words:
- the process assembles nucleotides to produce DNA
- but when the aciclovir gets inside the cell its phosphorylated and so binds to one of the virus’s enzymes. - the phosphate is added and turns into aciclovir triphosphate and then the cell thinks that the aciclovir triphosphate is one of the DNA precursors, so it tries to incorporate it into the DNA synthesis and therefore it inhibits the process of synthesis
what drug is used to treat the sight threatening viral necrotising retinitis caused by the Cytomegalovirus CMV
ganciclovir
what is ganciclovir and how is it administered
- Slow-release ocular implant
- inserted into the eye surgically
what is the epidemiology of acanthamoeba
a free living amoeba found in water / Soil
what are the 2 life cycles of acanthamoeba
- Mobile trophozoites
and - Dormant cysts
what 3 things is acanthamoeba resistant to
- freezing
- drying
- chlorine
what is acanthamoeba cultured as
Specialised, Non-nutrient agar / E. coli
what are the choices of drug and concentration for treating acanthamoeba
- Propamidine 0.1% and Polyhexamethylene biguanide (PHMB) 0.02%
- Chlorhexidine 0.02%
how often should the drugs to treat acanthamoeba be administered
hourly day and night for 2 days then reduce as condition improves
which drugs to treat acanthamoeba have activity against the cyst form
- Polyhexamethylene biguanide (PHMB)
and - Chlorhexidine
what stage of acanthamoeba keratitis will no drug be effective and what will be the only thing to treat it
- ring infiltrate
- will need corneal transplant
