Download Understanding eye medications

Natasha Mitchell MVB DVOphthal MRCVS
Understanding eye medications and discharging the ophthalmic patient
Abstract:
There are a wide range of ophthalmic medications used in dogs and cats, and there can be
confusion about what each product is used for. It is important to stock a range of medications so
that the most appropriate one is available when needed. Most ophthalmic preparations are
human medications, and therefore a prescription can be supplied if a medication is needed
promptly. The following is a discussion of ophthalmic medication available in Ireland along with
their uses. Tips are given for discharging the ophthalmic patient after a procedure such as
surgery.
Topical antibiotics
Broadly speaking, topical antibiotics are given for surface eye disease (for example infection of
the eyelids, conjunctiva or cornea) whereas systemic antibiotics are given for intraocular or
more serious infections (for example uveitis or a deep corneal ulcer). Antibiotics are over-used
in veterinary medicine in general, and they should only be given when an infection is suspected
or would result in harm.
Gentamycin 0.3% eye and ear drops
Mainly Gram negative activity
Amdipharm Limited
Pseudomonas - Melting ulcers?
Chloramphenicol 0.5% eye drops
Broad spectrum, good corneal penetration
Martindale Pharmaceuticals Ltd
Good when epithelium intact or deep ulcer
Chloramphenicol eye ointment 1%
As above
Martindale Pharmaceuticals Ltd
Avoid ointment with deep ulcers
Exocin 0.3% eye drops
Broad spectrum but more Gram negative
than positive – melting corneal ulcers
Allergan
Fucithalmic
Licensed for cats, dogs and rabbits
Dechra
Mainly Gram positive, carbomer base
Opticlox
Licensed for cows, horses (food) and
sheep
Norbrook
Gram positive
Topical anti-inflammatories
Topical anti-inflammatories can either be steroids or non-steroidal anti-inflammatory agents
(NSAIDs). Steroids are contraindicated if there is a corneal ulcer (in other words, if there is
fluorescein uptake). NSAIDs are preferred if the patient is diabetic because a small amount of the
drug will be absorbed systemically, particularly if the eye is inflamed or immediately following
surgery. Steroids can interfere with diabetic control with insulin by altering glucose levels. Systemic
steroids or NSAIDs are given for more serious conditions such as uveitis.
Topical steroids:
Maxidex 0.1% eye drops
Superficial ocular inflammation
Alcon
Anterior uveitis
Maxidex 0.1% eye ointment
As above
Alcon
Longer contact time, less frequent
application
Betnesol eye, ear and nasal drops
Superficial ocular inflammation
RPH Pharmaceuticals AB
Betnesol 0.1% eye ointment
As above
RPH Pharmaceuticals AB
Longer contact time, less frequent
application
Pred forte 1% eye drop suspension
Pannus
Allergan
Uveitis
FML liquifilm 0.1%
Superficial ocular inflammation
Allergan
FML forte liquifilm
Increased strength
Allergan
Anterior uveitis / pannus
Combination steroid / antibiotic drops
Maxitrol eye drops, Alcon
Dexamethasone, Neomycin, Polymyxin B
Inflammation plus infection
Maxitrol eye ointment, Alcon
Dexamethasone, Neomycin, Polymyxin B
Betnesol-N eye eye, ear and nasal drops
RPH Pharmaceuticals AB
Betnesol-N eye ointment
UCB Pharma Limited
FML / Neo liquifilm 1/5 mg/ml
Allergan
NSAIDs
Acular
When topical steroid undesirable e.g. diabetes
Ketorolac, Allergan
Don’t use with deep or melting ulcer
Glaucoma medication
Glaucoma is the result of a raised intraocular pressure. It is very painful and leads to
irreversible blindness. Blindness can occur very rapidly, and it is important that the owners
know that they must religiously apply the medication as directed by the vet. Ideally the
pressure-lowering response to the medication should be monitored by tonometry.
Trusopt (dorzolamide)
Carbonic anhydrase inhibitor
MSD and others
Reduced production of aqueous humour
qid
Azopt (brinzolamide)
Carbonic anhydrase inhibitor
Alcon
Reduced production of aqueous humour
tid
Xalatan 0.005% (latanoprost)
Prostaglandin analogue, increased
drainage of aqueous, contraindicated if
uveitis
Pharmacia Ireland Limited and others
Travatan 0.004% (travoprost)
Alcon
Prostaglandin analogue, increased
drainage of aqueous, contraindicated if
uveitis
Timoptal
Β-blocker
Side effects miosis, local irritation,
MSD or Wockhardt UK Ltd
bradycardia
Cosopt (dorzolamide plus timolol)
Not commonly used in small animals
Several, including MSD
Immunosuppressants
Certain immune-mediated ocular conditions respond very well to topical immunosuppression
treatment. Examples include dry eye (keratoconjunctivitis sicca), pannus and eosinophilic (or
proliferative) keratitis in cats. These drugs are powerful and the owner must not get them on
their own skin. At the start they could wear gloves when applying it to ensure they don’t get any
on themselves. However, with a little practice, it is usually simple for them to apply. They could
wash their hands if not wearing gloves.
Optimmune is a long-term medication, and it is common for an animal to need to continue with
treatment with life. Sometimes the vet will reduce the dose but may have to increase it again. It
is normally started twice daily. The tube is inflated with air so they owner might think that they
have been sold a faulty tube, but this is normal. They should be told not to role up the tube (like
some people do with tooth-paste) as they go along, as this can crack the tube and result in
product loss.
Before applying Optimmune, any ocular discharge that is present should be gently cleansed
from the eye. If this is not done, the drug is not going to work as effectively. The ointment may
be applied to the cornea or to the conjunctiva at the back of the eyelids. A small amount is
sufficient, about the length of a rice grain. If I find owners needing more than one tube a month,
I usually demonstrate how to apply it to ensure they are not applying too much. Applying an
excessive quantity does not improve the eye condition, and therefore it is wasteful. If the
owners complain that they squeeze out too much ointment and cannot retract it, I suggest that
they store the Optimmune in the fridge. This makes it more difficult to squeeze the tube, and
therefore there is more control over what comes out of the nozzle. However in normal
circumstances, it is not necessary to store Optimmune in the fridge.
The benefits of Optimmune are not immediately apparent. Treatment needs to continue for 4-6
weeks before it achieves maximal effect. If it is being used to treat keratoconjunctivitis sicca,
there is no need for the owner to withhold treatment on the morning of a follow-up
appointment, as it doesn’t have an immediate effect on the Schirmer tear test result.
Optimmune 0.02%
Suppresses T-cells; KCS, pannus,
Merck Animal Health
episcleritis
Proliferative eosinophilic keratitis in cats
Protopic 0.03% ointment
Off-label use, full effects not known, CARE!
Astellas Pharma Europe BV
KCS when Optimmune not effective
Artificial tears
There are several types of artificial tears available. Recently, some have been marketed in
Ireland for animals. They are usually multi-dose solutions which contain preservatives, but
single use vials without preservatives are useful if the pet seems irritated by the medication.
Artifical tears may be drops, gel or ointment. Ointment lasts the longest length of time but tends
to blur vision, and for this reason is usually used only at bed-time. Gels are very popular,
especially carbomer gel. Common trade names in this country include Vidisic and Gel Tears.
Drops are uncommonly used as the effect is so short-lived, although drops containing
hyaluronic acid do last longer than regular aqueous tear preparations.
Carbomer 980
Vidisic / Gel Tears
Gel, good contact time, still qid
Acetyl cysteine (Ilube)
Mucolytic. KCS with much mucous
Melting ulcers but stop once melt
improves
Hylo-Tear 0.1% sodium hyaluronate
Single use or multi-use vial
URSA Pharm
Viscoelastic gel with mucomimetic
properties
Hylo-Forte 0.2% sodium hyaluronate
URSA Pharm
Lacrilube
Longer contact time but blurs vision
At bed-time for KCS
Mydriatics
Mydriatics are drugs that dilate the pupil. They are used in two situations clinically. During the
ocular examination, the short-acting drug tropicamide is applied. This takes 20 minutes to work
and lasts on average 6 hours. By dilating the pupil, the vet can examine the lens and fundus
much more thoroughly. The second situation is when there is miosis (a constricted pupil) due to
uveitis. This may be due to immune-mediated disease or secondary to a corneal ulcer, among
many other possible causes. By dilating the pupil, several potentially harmful events are
avoided. It stops the edge of the pupil sticking to the lens (called a posterior synechia). If that
happens, there might be permanent opacity of the lens capsule as pigment is left behind. The
peripheral edge of the iris can also swell and stick to the cornea, and this or posterior synechia
can interrupt the normal circulation of aqueous humour within the eye, and that causes
glaucoma which leads to irreversible blindness. Another good effect of mydriatics is that they
paralyse intraocular muscles which spasm when they are inflamed, and thus they improve the
over-all comfort of the eye. Tropicamine is excellent for short-term dilation and is very useful in
cats which can resent atropine. Atropine is useful because it lasts much longer and therefore can
be applied less frequently. However it dries the ocular surface in some circumstances, and so
shouldn’t be used in animals with dry eye. It can raise the intraocular pressure and so is avoided
in glaucoma patients. After application, some of the medication runs down the tear duct and into
the mouth. It has a bitter taste and some dogs (and many cats) will start to salivate profusely
and seem quite irritated for 1-3 minutes. It is important to warn owners about this so that they
don’t think that their pet is having a seizure.
Tropicamide 0.5% or 1%
Single use vial (discard after 24 hours)
Minims vials, Chauvin Pharmaceuticals Ltd
Short-acting, for diagnosis or treatment
Atropine 1%
Single use vial (discard after 24 hours)
Minims vials, Chauvin Pharmaceuticals Ltd
Long-acting, for treatment only
Topical anaesthetic agents
Topical anesthetic drugs numb the cornea by acting on the sensory nerve endings of the
Trigeminal Nerve (Cranial Nerve V). They are available only as Minims vials. Proxymetacaine
(also called proparacaine in the USA) is a useful preparation as it is potent and works quickly
(within 30 seconds). It sometimes makes the conjunctiva a little red but otherwise it is well
tolerated. It must be stored in the fridge. Tetracaine (also called amethocaine in the USA) is also
potent and works in 30 seconds, and it doesn’t need to be stored in the fridge. However in
general it causes more ocular irritation and occasionally a mild allergic reaction which
chemosis. They are used to facilitate diagnostic tests such as tonometry and distinguishing
spastic from anatomical entropion. They are also used to facilitate examination of a painful eye.
They are epitheliotoxic and therefore will inhibit healing of a corneal ulcer. For this reason, they
must never be dispensed to an owner to apply as treatment at home.
Proxymetacaine 1%
Single use vial (discard after 24 hours)
Minims vials, Chauvin Pharmaceuticals Ltd
Store in fridge
Tetracaine 1%
Single use vial (discard after 24 hours)
Minims vials, Chauvin Pharmaceuticals Ltd
Keep at room temperature
Discharging the ophthalmic patient
Receiving clear instructions on discharge is a vital component of good post-op recovery and a
good surgical result. If there are complicated instructions, it would be very useful to supply
them in written form as well as going over them verbally. The vet should have already explained
to the owner what was wrong with the eye and the surgical procedure.
They will probably be discharged wearing a buster collar, and it is important that the owner
understands the importance of leaving this on for the recommended period of time. If the dew
claws were bandaged, this should be pointed out (there may also be a bandage on the site where
the catheter was placed) and routine advice given about not getting them wet, watching for toe
swelling and when to remove them (usually 2-3 days).
Medications should be individually and clearly labeled. The owner always asks when they
should give the first dose, and this of course depends on what peri-operative injections were
given. Owners can find it difficult to apply eye medications and to understand why they are
required. It is the role of the veterinary nurse to help explain to the owner the importance of
applying the medication as directed by the vets, and to demonstrate to them how they might
apply it easily and effectively. The following are a list of instructions that can be explained to or
printed out for the owner.
HOW DO I APPLY EYE MEDICATIONS?
It is important to store eye medications correctly. All need to be stored below 25ºC. Some need
to be kept in the fridge (including Chloramphenicol, Xalatan until opened and Serum). The
majority need to be discarded 28 days after opening, but some expire sooner.
Eye medications may be drops, gels or ointments. Where a combination of these formulations
has been dispensed, first apply the drops, then the gel, then the ointment.
Gently invert the dropper bottle a couple of times to make the suspension uniform.
The animals head should be slightly elevated. This is achieved by placing one hand under the
chin. The other hand holds the dropper bottle, and this hand may rest against the animals
forehead in order to steady it, and to feel if the animal is going to make a sudden movement.
The drop or ointment should be applied to the centre of the cornea (the clear window of the
eye). If the drop misses the eye, another attempt can be made straight away.
Care should be taken that the nozzle does not come into contact with the cornea. This is to
prevent trauma to the eye but also in order to keep the nozzle clean.
One drop is all that is required. A strip the size of a rice grain is all that is required when
applying ointment.
The animal should be allowed to blink, and where possible the head should remain slightly
elevated for a few seconds.
Where multiple medications are dispensed, allow at least five minutes between each
application.
It is useful to distract the animal immediately after applying eye medication to stop them from
rubbing at the eye. Feeding a meal or a treat, or taking them for a walk may provide a good
distraction. Some animals will have a buster (Elizabethan) collar which prevents them from
traumatizing the eye.
A standard 5ml bottle of eye drops contains approximately 100 drops.
By regularly applying eye drops, you get a chance to check the appearence of the eye. If any
changes concerns you, please contact your veterinary clinic immediately.
When drops are to be given several times a day, it is important that the owner is aware that
these need to as spread out as possible – for example, twice daily application means every
twelve hours, and four times daily means every 6 hours etc.
Do point out that the left eye refers to the animal’s left eye (therefore the right eye as the owner
looks at them) as this can often confuse owners and lead to medication being applied to the
wrong eye.
The owners are encouraged to cleanse the eye and eyelids if there is ocular discharge. They
could use previously boiled water soaked into cotton wool and squeezed out. This should be
done before applying topical medications.
Routine advice is given regarding eating, drinking and toileting on return home after the
anaesthetic.
A harness is a good idea as it prevents any pressure on the neck. Some harness designs don’t
have to be fitted over the head, and these are preferable for dogs that have to wear a buster
collar.
The owner should be given a time frame for when to expect an improvement. They should be
given instructions for when to call – for example if the eye is sore and squinting, or if vision is
suddenly lost. Depending on the surgery carried out, of course a small amount of redness or
swelling is expected. They should be encouraged to phone if they are in doubt, and a post-op
appointment should be made. Many stitches used in ocular surgery are dissolvable and
therefore don’t need to be removed, but wound healing still needs to be checked.
Further reading:
Veterinary Ophthalmology - a manual for nurses and technicians. Sally Turner. 2005. Elsevier.
ISBN 0750688416
Chapter 2: Ocular pharmacology and therapeutics
BSAVA Manual of Small Animal Ophthalmology. Simon Peterson-Jones and Sheila Crispin 2002.
BSAVA. ISBN 0 905214 54 4
Chapter 2: Ophthalmic surgery and anaesthesia
Chapter 3: Ophthalmic drugs