anti-infectives used in eyecare

• Professional guidance

  • Understand the various pharmacological and non-pharmacological approaches to disease management relevant to their practice and the risks and benefits of each option
  • Be able to make a decision about whether to sell or supply medicines using exemptions, based on a relevant examination, assessment and history taking
  • Be able to undertake a thorough, sensitive and detailed patient medical history, including an appropriate medication history
  • Be able to communicate information about medicines clearly with service users and others involved in their care
• Antimicrobial Stewardship

  • Consider alternative options and only prescribe antimicrobials when this is clinically appropriate
  • Be aware of local guidelines on antimicrobial prescribing
  • Not issue an immediate prescription for an antimicrobial to a patient who is likely to have a self-limiting condition
  • Only issue repeat prescriptions for antimicrobials if these are needed for a particular clinical condition or indication
• Bacterial resistance

  Bacteria change in response to the use of specific medicines by spontaneous mutation, by producing enzymes, or by altering the target sites, which significantly reduces the effectiveness of the drug and requires alternative anti-infective drugs
• Micro-organisms commonly causing eye infections

  • Microbes – bacteria, viruses, fungi
  • Parasites – protozoa
  • Viruses – no nucleus or chromosome but contain either DNA or RNA
  • Eukaryotic cells -nucleated (protozoa, fungi)
  • Prokaryotic cells – anucleate but have a chromosome (Bacteria)
• Prophylactic

  Prevention of infection
• Therapeutic

  Treat existing infection
• Reasons for use of anti-infective pharmaceuticals

  • Prophylactic (to prevent an infection developing)
  • Therapeutic (to treat an existing infection)
• Prophylactic use of anti-infective pharmaceuticals

  • Corneal abrasion – anti-infective agent to reduce the risk of infection
  • Bacterial conjunctivitis – antibiotic eye drop drug
  • Blepharitis – antibiotic cream to the eyelids – to reduce bacterial load
  • Hordeolum – anti-infective agent when in pain
  • Marginal keratitis – antibiotic to reduce the bacteria load
  • HSK (shared care/PGD) – to treat herpes simplex keratitis. Gancilocy gear
• Selecting a specific drug

  1. Symptoms and clinical signs

  2. Likely diagnosis

  3. Microbiological cultures (Sample / swab collected before tx commenced, Analysed in lab to identify causative agent (48-72 hours), Delay in tx may reduce chance of good outcome for px)

  4. Presumptive Method (Most likely causative agent based on examination & diagnosis, Select drug most effective for tx, Monitor px, Change tx when appropriate)

  5. Combination of both (In severe/ sight –threatening infections)
• Bacteria

  • Prokaryotic micro-organisms: their cell structure lacks a nucleus
• Classification of bacteria

  • Gram positive bacteria (take on the purple appearance of the Gram's stain)
  • Gram negative bacteria (do not retain the Gram's stain, appear pink due to a second stain)
• Bacteriostatic

  Slow down/stop the replication of bacteria
• Bactericidal

  Actively kill bacteria
• Common sites of action for antibacterials

  • Ribosomes – the site of protein synthesis
  • DNA gyrase – essential for bacterial replication
  • Cell wall – allows uptake of nutrients by passive diffusion
• Protein synthesis inhibitors

  1. Chloramphenicol (Bind to the 50S sub-unit of the ribosome, Disrupt the process of linking amino acids to form a peptide chain, Suppression of the 'peptidyl transferase' enzyme)

  2. Fusidic acid (Inhibits an enzyme called 'translocase' which is critical to the process of assembling proteins from a peptide chain of amino acids)
• Chloramphenicol

  • Commonly used, broad spectrum antibiotic, Potent broad spectrum (effective against both gram positive and some gram negative), Ineffective against pseudomonas aeruginosa, Bacteriostatic, Widely used due to broad spectrum, cost effectiveness, good corneal penetration, used in management of bacterial conjunctivitis, hordeolum, staphylococcal and seborrheic blepharitis, marginal keratitis
• Medicinal forms of Chloramphenicol

  • Chloramphenicol 0.5% eyedrops (5ml/10ml bottles and SDUs), Chloramphenicol 1% eye ointment, Generic products (POMs), Branded versions (P) of both 0.5% and 1% forms
• Branded (P) Chloramphenicol

  Licensed to treat bacterial conjunctivitis only, For aged 2 years old +, Minimum and Maximum 5 day tx
• Generic (PoM) Chloramphenicol

  Wider range of indications, For aged 1 month old +
• Fusidic Acid

  • Narrow spectrum antibiotic, highly effective against common gram positive bacteria (e.g. staphylococcus aureus) but NOT streptococcus pneumonia or gram negative bacteria (e.g. pseudomonas aeruginosa)
• Medicinal forms of Fusidic Acid

  • Fusidic acid 1% viscous eye drops 5g (PoM), For aged 1 month +
• Tetracyclines

  • Oral tablets, broad-spectrum antibacterials effective against both gram positive and gram negative bacteria, Bacteriostatic primarily, Bind to 30S sub unit of ribosomes
• Medicinal forms of Tetracyclines

  • Doxycycline (50/100mg tablets, PoM)
  • Minocycline (50/100mg tablets, PoM)
  • Oxytetracycline (250mg tablets, PoM)
  • Tetracycline (250mg tablets, PoM)
• Aminoglycosides

  • Bind to 30S subunit of ribosomes (additional effect on 50S subunit), Bacteriostatic & slow bactericidal action, Effective against many gram-negative bacteria and some gram positive
• Medicinal forms of Aminoglycosides

  • Gentamicin (0.3% Generic) (PoM)
  • Neomycin in combination with steroid products (PoM)
• Fluoroquinolones

  • Inhibits action of the enzyme DNA gyrase, Broad spectrum, Effective against a range of gram positive and gram-negative bacteria
• Medicinal forms of Fluoroquinolones

  • Ciprofloxacin (Ciloxan 0.3% eyedrops) (PoM)
  • Ofloxacin (Exocin 0.3% eyedrops) (PoM)
  • Levofloxacin (Levofloxacin generic 5mg/ml eyedrops)(PoM)
  • Moxifloxacin (Moxivig 0.5% eyedrops) (PoM)
• Polymyxin B

  • Broad spectrum of activity against gram negative bacteria, Poorly effective against gram positive bacteria
• Medicinal forms of Polymyxin B

  • Maxitrol – combination drug: Dexamethasone, Neomycin, Polymyxin B (Not available for use for non IP practitioners in its current combination form)
• Diamidines

  • Antibacterial, antiprotozoal and antifungal actions, Effective against some common gram positive bacteria (e.g. staphylococcus aureus) but not gram negative bacteria
• Medicinal forms of Diamidines

  • Propamidine isethionate 0.1% eye drops (Brolene eye drops) (P)
  • Dibrompropamidine 0.15% eye ointment (GoldenEye ointment)(P)
  • Propramidine isethionate 0.1% eye drops (GoldenEye drops) (P)
• Antivirals - mechanism of action

  Topical antiviral drugs are active against herpetic viral infections (simplex & zoster), Block the ability of the virus to replicate DNA, Aciclovir and ganciclovir are prodrugs (Inactive until metabolized within the eye, Active drug blocks DNA transcription, Leading to DNA that is fragmented and no longer functional, Virus fails to replicate, Selective toxicity)
• Medicinal forms of topical ocular antivirals

  • Aciclovir 3% ophthalmic ointment (Zoviraz) (PoM) – longterm stock/manufacturing problem
  • Gancilovir 0.15% eye ointment (Virgan) (PoM), 5 x daily until cornea healed then 3 x daily for 5-7 days
• Antifungals

  • Ophthalmic preparations not widely available, Fungal infections are rare, difficult to treat and have a poor prognosis, Patient is hospitalised and treated around-the-clock with antifungal drugs (topical and oral), Mechanism of action is disrupting the function of the fungi plasma membrane, Toxic to cornea & conjunctiva
• Medicinal forms of antifungals

  • Nystatin
  • Amphotericin