Ophthalmic and Otic drugs

Mydriasis: Dilation of the pupil.
Cycloplegic: A drug that paralyzes the ciliary body, resulting in decreased pain.
Dosage Forms: Atropine sulfate

Miosis: Constriction of the pupil.
Cholinergic Drugs: These drugs cause constriction of the pupil and reduce intraocular pressure (IOP) by increasing the outflow of aqueous humor.
Uses: Primarily used to reduce IOP in glaucoma.
Side Effects: May include local irritation and redness.
Dosage Form: Pilocarpine

Definition: A group of diseases characterized by increased intraocular pressure (IOP).
Consequences of Untreated Glaucoma: Damage to the retina and potential blindness.
Aqueous Humor Production: Produced by the ciliary body behind the iris. The process is controlled by the enzyme carbonic anhydrase.
Movement: Aqueous humor moves from the posterior chamber through the pupil into the anterior chamber and is drained from the eye through a sponge-like meshwork.

Classes:
  1. Carbonic Anhydrase Inhibitors
     - Function: Reduce IOP.
     - Side Effects: Vomiting, diarrhea, weakness.
     - Dosage Forms:
       - Dichlorphenamide (Daranide®)
       - Acetazolamide (Diamox®)
  2. Beta-Adrenergic Blockers
     - Function: Reduce IOP.
     - Example: Timolol (Timoptic®) - used to prevent glaucoma in the contralateral eye

Fluorescein Dye: Adheres to areas of corneal loss. The cornea is fat soluble, and underlying tissue is water soluble. Fluorescein, being water soluble, can adhere to underlying tissue, making it useful for diagnosing corneal ulcers and lacerations
- Lacrimal duct is connected to the nasolacrimal system, facilitating tear drainage from the eye into the nasal cavity. May see dye coming from nose.

Purpose: Measures tear production to diagnose keratoconjunctivitis sicca (dry eye).This test involves placing a small strip of blotting paper in the lower eyelid for a specified duration. A reading of less than 10 mm of wetting after 5 minutes is indicative of inadequate tear production, supporting the diagnosis of dry eye.

Indication: Used to treat keratoconjunctivitis sicca (KCS) by suppressing the immune system.
Effect in Dogs: Increases tear production.
Efficacy in Cats: Not effective.
Side Effects: No apparent side effects noted.

Common Dosage Forms: Vetropolycin, Trioptic-P.
Applications: Treat and prevent ocular bacterial infections, including conjunctivitis, corneal ulcers, wounds, and certain forms of keratitis. Often employed before and after eye surgeries. Available in ointment and solution forms.

Common Types: Vetropolycin HC® and Trioptic-S®.
Composition: Combines an antibiotic with a steroid.
Function: Reduces inflammation and fights bacteria, primarily used for treating conjunctivitis.
Cautions: Should not be used in dogs with corneal ulcers or in cats with conjunctivitis; available in ointment or solution forms.

Action: Antibiotic that inhibits bacterial growth by suppressing protein synthesis (bacteriostatic).
Spectrum: Effective against a wide range of bacteria and protozoa.
Approval Status: Approved only for use in livestock; extra-label use in other animals.
Use in Cats: Employed to treat conjunctivitis; contraindicated in pregnant animals.

Type: Topical antiviral agent.
Mechanism: Interferes with the virus' DNA production.
Application: Treats conjunctival and corneal disease associated with feline herpesvirus.
Use in Dogs: Not commonly used; extra-label use is noted.
Side Effects: Can cause irritation.

Structure Reference: Fig. 10-3. Displays structures of the ear, including pinna, vertical canal, and tympanic membrane (Copyright 2009 by Saunders, Elsevier Inc.).

Otitis Externa: Inflammation of the outer ear, characterized by swollen and reddened ears and partial occlusion of the ear canal due to hyperplasia. Accompanied by inflammatory exudate.
Otitis Media: Inflammation of the middle ear, with signs including exudate in the tympanic bulla and possible osteomyelitis.
Otitis Interna: Inflammation of the inner ear, associated with neurologic changes like head tilt and circling.

Components:
  - History taking.
  - Physical examination.
  - Ear examination.
  - Ear cultures.
  - Thyroid hormone level checks.
  - Intradermal skin testing.
  - X-rays.
  - Therapeutic trials with insecticides and hypoallergenic diets.

Procedures:
  - Removal of ear-canal hair.
  - Ear cleaning.
  - Topical application of anti-bacterials and corticosteroids.
  - Systemic antibacterials.
Dietary Plan: Customized diet based on individual patient evaluation.
Systemic corticosteroids may be included.
Surgery as a potential option for severe cases.

Types: Mainly anti-infective (antibacterial, antifungal, anti-parasitic), often anti-inflammatory or both.
Cautions: Many preparations are ineffective in the presence of debris; the ear canals should be cleaned prior to application. These drugs should generally not be used if there is a ruptured eardrum, necessitating prior examination
Many of these drugs should NOT be used in the presence of a ruptured ear drum so an examination is necessary first.

Purpose: Clean the ears of cerumen (earwax) and debris while controlling odors.
Application Method: If excessive debris is present, flush gently using a bulb syringe; if pain is too high, general anesthesia may be required.
Composition: Can include antiseptics, anesthetics, and antimicrobial agents.
Common Dosage Forms:
  - Epi-Otic
  - Oti-Clens
  - Novalsan Otic
  - Mal-A-Ket

Function: Topical antibiotic otic drugs used to treat bacterial infections; often contain anti-inflammatory agents to alleviate inflammation and pruritus.
Common Dosage Forms:
- Gentamycin sulfate (Otomax, Gentocin Otic Solution, Mometamax).
- Caution: Potential side effect includes ototoxicity; tympanic membrane integrity must be ensured.

Target: Specifically treat ear mites (Otodectes cynotis), frequently seen in puppies and kittens

Common Dosage Forms Used: Ivermectin (Acarexx), Milbemycin (MilbeMite), and Selamectin (Revolution).

Example: Fluocinolone combined with DMSO (Synotic®) which enhances percutaneous absorption; caution is advised to avoid contact with skin (wear gloves and wash hands after use).