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eye

purohit pharm

QuestionAnswer
Drugs used in ophthalmic practice are generally the same those used for organs & systems, can be used or administered for the treatment of ophthalmic conditions or diseases.
With a few exception, the mechanism of action of these drug is similar to those targeted for other systems.
Administration routes for ophthalmic therapy may include topical, subconjunctival & systemic.
Special Considerations in Ophthalmic Location of the lesion,The tissue drug concentration,Ease of application &,Properties of the drugs.
The blood-ocular barriers:Drug penetration are complex & protective mechanisms that complicates drug delivery.
There are differences in normal vs diseased corneal & conjunctival tissues due to compromised epithelium.
Uninflamed vs inflamed eye.
Topical Ophthalmic Therapy,It could be in the form of eye drops, ointments, drug impregnated inserts & contact lenses.
Eye drops Delivery volume, frequency of application, subpalperal lavage or reverse nasolacreimal lavage (specially in horses).
Increasing the viscosity of eye drops & using drug suspensions, emulsions & liposomes.
Ointments have much longer contact time than eye drops.
In some cases topical medication may be difficult therefore drugs have to administered by subconjunctival injection or systemically.
Subconjunctival Ocular Injections Can be given either under the eye ball conjunctiva (epibulbar) or underneath the conjunctiva lining of the eyelid (subpalpebral), or retrobulbar.
Indicated for the treatment of lesions in the cornea, sclera, anterior uvea & vitreous or aqueous humor.
This procedure allows drugs to by pass the epithelium which is the main barriers that limit drug entry.
This technique is used in severe conditions that require high drug concentration.
Systemic Therapy,In a normal eye the blood-eye barriers limits the amount of drug penetration into the eye.
if the eye is inflamed the normal impermeability of these barriers is greatly reduced, thus increases drug concentration into the target tissue of the eye.
Systemic treatment can be used to treat condition of eyelids, vitreous, retina, optic nerve & retrobulbar area, etc.
Apart from oral doxycycline, systemic therapy may not provide adequate therapy for cornea & conjunctival condition.
Drug characteristics pH= 6.5,Some drugs need to buffered, e.g. pilocarpine is very irritating.
Ointments appears to be less irritating than drops for highly concentrated drugs.
Increased viscosity have much longer contact time.
Wetting agents Reduce surface tension, increase penetration of ionized drugs.
Autonomic Drugs,Miotic agents constricts the pupil.
Mydriatic agents dilates pupil.
Cholinergic stimulants (parasympathomimetics) Has muscarinic effects of acetylcholine (Ach).
Pilocarpine The principal uses are for the treatment of primary glaucoma, stimulates lacrimation.
Carbachol is not lipid soluble so it is combined with a wetting agents such a benzylalkonium chloride
Ach Used for constriction of pupil during surgery (last about 10 min.).
Indirect acting cholinergics,Cholinesterase inhibitors allows Ach to persist.
Ecthothiophate Control of primary glaucoma.
Physostigmine Short acting
Mydriatics dilate the pupil.
Cholinergic antagonists Atropine,Tropicamide,Other, seldom used are: homatropine, scopolamine & cyclopentolate.
Mydriatics,Adrenergic agents,Adrenergic agonists are Epinephrine,Dipivalyl epinephrine,Phenylephrine. Phenylephrine,It
Mydriatics cont,Selective alpha-2 agonists Apraclonide,Brimonidine.
Beta adrenergic blockers Timolol,Levobunolol.
Intraocular inflammation with infections reduces or eliminates blood-ocular barriers to drug penetration, so these drug can be used treat infection, similar to their use in soft tissue infection.
Antibacterial agents There are topical preparations available for use in eye,Some times systemic administration is also done.
Antiviral Pyrimidine nucleoside analogs such as Idoxuridine & triflurothymidine,Purine nucleoside:Adenine arabinoside,Acyclovir is guanidine derivative of vidarabine,Gangciclover,cidofovir & penciclovir r new compounds,Betadine 1:20 dilution of disinfectant,Interfe
Antifungals Betadine & tincture of iodine: 1:10 or 1:20 dilution in saline for eye irrigation,Silver sulfadiazine:Broad spectrum antibacterial & antifungal dermatologic cream used topical.
Azoles: Imidazoles such as Itraconazole, miconazole, clotrimazole, ketoconazole & fluconazol.
Polyene macrolide antibiotics Natamucine, Amphotericin, Nystatin.
Excessive inflammation requires prompt & judicious use of these drugs in clinical practice.
Both corticosteroids & nonsterodial anti-inflammatory (NSAIDs) drugs haven used very effectively.
Topical Prednisolone acetate, Dexamethasone, Hydrocortisone etc.
Subconjunctival Betamethasone, dexamethasone.
Systemic use Prednisolone.
Contraindications In all cases of corneal ulceration & any corneal wound or infection.
Adverse effects Potentiation of corneal ulcer. Topical corticosteroids should never be applied to an ulcerated cornea or the one likely to ulcerate,in this type of cases system use of NSAID is preferred, rather than corticosteroid for treatment of melting cornea.
Nonsteroidal Anti-inflammatory Drugs,Topical Flurbiprofen, diclofenac, suprofen, ketolorac.
Systemic Flunixin meglumine, carprofen, deracoxib, phenylbutazone, aspirin.
Immunomodulating Drugs Azathioprine.
Cytotoxic immunomodulating agents Cytosin arabinoside,Procarbazine, Chlorambucil. Mitoxantrone, Tetracylicne & niacinamide combined.
T- lympocyte inhibitors(calcineurin inhibitors) Cyclosporine,Tacrolimus.
Antiallergic, Antihistaminic Agents ,H1-antihistamines
Mast cell stabilizers cromolyn sodium, lodoxamide.
Vasoconstrictors (decongestants) Naphazoline, tetrahydrozoline, etc.
Topical Anesthetics Proparacaine 0.5 % solution,Lidocaine,Tetracaine,Ointment or solution,Piperocaine,Dibucaine,Benoxinate.
Carbonic Anhydrase Inhibitors,Systemic preparations Acetazolamide,dichlorphenamide,methazolamide, ethoxzolamide,Long term medical management of glaucoma.
Topical preparations,Dorzolamide, brinzolamide,are used to reduce IOP.
Note: Systemic osmotic diuretics such as mannitol (IV) or oral glycerin have been used to reduce IOP.
Tear Substitutes Methylcellulose, hydroxy-propyl-methylcellulose, carboxy-methylcellulose,Polyvinyl alcohol, polyvinal pyrrolidone (mucomimetic)Hyaluronic acid for prolong retentation, & improved tear film stability.
Mineral oil, white petrolatum, lanolin for maximum retention,Lubricate the surface of the eye for comfort. etc.
Created by: alljacks
 

 



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