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Ocular Pharmacology PowerPoint Presentation

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Description : Check out this medical presentation on Pharmacology, which is titled "Ocular Pharmacology-I", to know about pharmacokinetics and pharmacodynamics of ocular drugs, ocular routes of drug administration, and topical antibiotic and cycloplegic agents.

Tags : Pharmacology, Ocular Pharmacology, pharmacokinetics, pharmacodynamics

Published on : Jul 18, 2021 | Views : 2361 | Downloads : 8

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Ocular Pharmacology-I Dr. Ajai Agrawal Additional Professor Department of Ophthalmology A.I.I.M.S., Rishikesh
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Learning Objectives At the end of this class students shall have a basic understanding of : pharmacokinetics and pharmacodynamics of ocular drugs Ocular routes of drug administration Topical antibiotic and cycloplegic agents 2
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Overview 3
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Anatomy of Eye 4
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Tear Film 5
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Pharmacodynamics It is the biological and therapeutic effect of the drug (mechanism of action) Most drugs act by binding to regulatory macromolecules, usually neurotransmitters or hormone receptors or enzymes If the drug is working at the receptor level, it can be agonist or antagonist If the drug is working at the enzyme level, it can be activator or inhibitor 7
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Pharmacokinetics It is the absorption, distribution, metabolism, and excretion of the drug A drug can be delivered to ocular tissue as: Locally: Eye drop Ointment Periocular injection Intraocular injection Systemically: Orally IV 8
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Pharmacokinetics of Ocular Drugs Classical pharmacokinetic theory based on systemically administered drugs does not fully apply to all ophthalmic drugs Topical route – most commonly used 9
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Absorption Rate & extent of absorption of topically instilled drugs depends upon – “Drug penetration into the eye is approximately linearly related to its concentration in the tear film.” Time the drug remains in the cul-de-sac & precorneal tear film Elimination by nasolacrimal drainage Drug binding to tear proteins Drug metabolism by tear & tissue proteins Diffusion across cornea & conjunctiva 10
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Distribution Transcorneal absorption Accumulation in aqueous humor Distribution to intraocular structures Trabecular meshwork pathway Distribution to systemic circulation 11
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Distribution Melanin binding of certain drugs – - Eg: 1. Mydriatic effect of alpha adrenergic agonists slower in onset - darkly pigmented irides compared to those with lightly pigmented irides 2. Atropine’s mydriatic effect – long lasting in non-albino rabbits than in albino rabbits 3. Accumulation of chloroquine in retinal pigment epithelium – Bull’s eye maculopathy 12
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Metabolism Enzymatic biotransformation of ocular drugs- significant Esterases – particular interest Eg: Development of prodrugs for enhanced ocular permeability Dipivefrin hydrochloride Latanoprost 13
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Drug Delivery in Eyes Topical Periocular Intraocular Systemic drop ointment gel Soft contact lens Subconjunctival Subtenon Peribulbar Retrobulbar Intracameral Intravitreal Oral intravenous Intramuscular
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Ocular Routes of Drug Administration 16
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Factors influencing local drug penetration into ocular tissue Drug concentration and solubility: higher concentration -- better penetration e.g pilocarpine 1-4% but limited by reflex tearing Viscosity: addition of methylcellulose and polyvinyl alcohol increases drug penetration by increasing contact time with cornea and altering corneal epithelium Lipid solubility: higher lipid solubility- more penetration 17
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Factors influencing local drug penetration into ocular tissue Surfactants: preservatives alter cell membrane in cornea and increase drug permeability e.g. benzylkonium and thiomersal pH: the normal tear pH is 7.4 If drug pH is much different, this will cause reflex tearing Drug tonicity: when an alkaloid drug is put in relatively alkaloid medium, the proportion of the uncharged form will increase, thus more penetration Molecular weight and size 18
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TOPICAL Drop (Gutta)- simplest and most convenient mainly for day time use 1 drop=50 microlitre Conjuctival sac capacity=7-13 micro liter so, even 1 drop is more than enough Method hold the skin below the lower eye lid pull it forward slightly INSTILL 1 drop measures to increase drop absorption: -wait 5-10 minutes between drops -compress lacrimal sac -keep lids closed for 5 minutes after instillation 19
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Ointments Increase the contact time of ocular medication to ocular surface, thus better effect It has the disadvantage of blurring vision The drug has to be highly lipid soluble with some water solubility to have maximum effect as ointment 20
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Peri-ocular injections They reach behind iris-lens diaphragm better than topical application E.g. subconjunctival, subtenon, peribulbar, or retrobulbar This route bypass the conjunctival and corneal epithelium which is good for drugs with low lipid solubility (e.g. penicillins) Also steroids and local anesthetics can be applied this way 21
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Periocular Subconjunctival - To achieve higher concentration Drugs which cannot penetrate cornea due to large size Penetrate via sclera Subtenon—Ant. Subtenon– diseases anterior to the lens Post. Subtenon– disease posterior to the lens Retrobulbar- Optic neuritis Papillitis Posterior uveitis Anesthesia Peribulbar-- anesthesia 22
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Intraocular injections Intracameral or intravitreal E.g. Intracameral acetylcholine (miochol) during cataract surgery Intravitreal antibiotics in cases of endophthalmitis Intravitreal steroids in macular edema Intravitreal Anti-VEGF for DR 23
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Sustained-release devices These are devices that deliver an adequate supply of medication at a steady-state level E.g. Ocusert delivering pilocarpine Timoptic XE delivering timolol Ganciclovir sustained-release intraocular device Collagen shields 24
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Systemic drugs Oral or IV Factor influencing systemic drug penetration into ocular tissue: lipid solubility of the drug: more penetration with high lipid solubility Protein binding: more effect with low protein binding Ocular inflammation: more penetration with ocular inflammation 25
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Therapeutic applications of Drugs in Ophthalmology 26
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Common ocular drugs Antibacterials (antibiotics) Antivirals Antifungals Mydriatics and cycloplegics Antiglaucoma medications Anti-inflammatory agents Ocular Lubricants Local anesthetics Ocular diagnostic drugs Ocular Toxicology Corticosteroids NSAID’s 27
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Topical Antibacterial Agents Commercially Available for Ophthalmic Use H- Hypersensitivity ; D-RCD – Drug Related Corneal Deposits 28
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Topical Antibacterial Agents Commercially Available for Ophthalmic Use….. 29
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Antibacterials( antibiotics) Penicillins Cephalosporins Sulfonamides Tetracyclines Chloramphenicol Aminoglycosides Fluoroquinolones Vancomycin Macrolides 30
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Antibiotics Used topically in prophylaxis (pre and postoperatively) and treatment of ocular bacterial infections. Used orally for the treatment of preseptal cellulitis e.g. amoxycillin with clavulanate, cefaclor Used intravenously for the treatment of orbital cellulitis e.g. gentamicin, cephalosporin, vancomycin, Can be injected intravitrally for the treatment of endophthalmitis 31
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Specific antibiotic for almost each organisms Sulfonamides- Chlamydial infections like TRACHOMA INCLUSION CONJUNCTIVITIS TOXOPLAMOSIS Bacterial cell wall synthesis inhibitors- Penicillin Cephalosporins I) First generation- Gram + cocci eg cephazoline ii) Second generation —Gram – ve and antistaphylococcal— cefuroxime iii) Third generation– Gram –ve bacilli --ceftriaxones 32
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Side effects- allergic reaction neutropenia thrombocytopenia Amino glycosides Mainly against gram negative bacilli Bacterial protein synthesis inhibitors Gentamycin- 0.3% eye drops Tobramycin- 0.3% eye drop Neomycin— 0.3-0.5% eye drops Amikacin ----- 1% eye drops 33
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Tetracycline Inhibit protein synthesis active against both gram+ and gram -ve, some fungi and Chlamydia Chloramphenicol Broad spectrum ,bacteriostatic, gram+/gram-ve, Chlamydia 0.5% Eye drops, ointment 34
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Fluoroqinolones Most frequently used topical broad spectrum antibiotics Ciprofloxacin – 0.3% eye drops Ofloxacin - 0.3% eye drops Moxifloxacin - 0.5 % eye drops Levofloxacin and Besifloxacin eye drops 35
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Antibiotics Trachoma can be treated by topical and systemic tetracycline or erythromycin, or systemic azithromycin. Bacterial keratitis (bacterial corneal ulcers) can be treated by topical fortified cephalosporins, aminoglycosides, vancomycin, or fluoroquinolones. Bacterial conjunctivitis is usually self limited but topical erythromycin, aminoglycosides, fluoroquinolones, or chloramphenicol can be used 36
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Dacryocystitis - Infection of the lacrimal sac 37
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Hordeolum/ Stye – Infection of the meibomian, Zeis or Moll gland 38
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Conjunctivitis – Inflammatory process of the conjunctiva 39
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Blepharitis – Bilateral inflammatory process of the eyelids 40
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Antiviral Agents for Ophthalmic Use PK – Punctate Keratopathy ; H - Hypersensitivity 41
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Antiviral Agents for Ophthalmic Use… 42
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Antivirals Acyclovir- Most commonly used anti-viral 3% ointment 5 times-10-14 days 800mg oral 5 times 10-14 days Intravenous for Herpes zoster retinitis Others Idoxuridine Vidarabine Cytarabine Triflurothymidine Gancyclovir INDICATIONS HZ keratitis Viral uveitis 43
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VIRAL DENTRITIC ULCER 44
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CMV Retinitis 45
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Antifungal Agents for Ophthalmic Use 46
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ANTIFUNGAL INDICATIONS Fungal corneal ulcer Fungal retinitis/ Endophthalmitis Commonly used drugs are Polyenes damage cell membrane of susceptible fungi e.g. amphotericin B, natamycin, nystatin side effect: nephrotoxicity Imidazoles increase fungal cell membrane permeability e.g. miconazole, ketoconazole,fluconazole Flucytocine act by inhibiting DNA synthesis 47
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Mydriatics and cycloplegics Dilate the pupil, ciliary muscle paralysis CLASSIFICATION Short acting- Tropicamide (4-6 hours) Intermediate- homatropine ( 24 hours) Long acting- atropine (2 weeks) Indications corneal ulcer uveitis cycloplegic refraction 49
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Thank you 51