otic and opht

DOSAGE FORMS FOR THE EYE AND EAR

Learning Objectives

  • Upon completion of this section, students should be able to:

    • Describe dosage forms for the ear and eye, and the conditions that they treat.

    • Differentiate between the properties of otic (ear) and ophthalmic (eye) dosage forms.

THE EAR

Key Factors Affecting the Preparation of Dosage Forms for the Ear

  • Structure of the Ear Canal and Ear Drum:

    • The anatomy and physiology of the ear are crucial in the formulation of effective medications, as they influence how products are absorbed and utilized within the ear.

  • Cerumen (Ear Wax):

    • The presence of cerumen can affect the delivery and efficacy of otic medications.

OTIC (Ear) Products

  • Conditions Treated with Otic Preparations:

    1. Inflammation:

    • Use of anti-inflammatory medications.

    1. Swimmer's Ear:

    • Treatment example: Burosol Otic, which helps to keep the ear dry.

    1. Wax Build-Up:

    • Treatment example: Cerumenex.

    1. Outer Ear Infections:

    • Treatment example: Polysporin.

  • Base of Otic Products:

    • Common bases may include glycerin or propylene glycol.

    • Most otic preparations are NOT safe for ophthalmic use (e.g., antibiotic corticosteroid combinations such as Cipro HC).

Otic/Ophthalmic Dosage Forms

  • Some solutions can function as both otic and ophthalmic (e.g., Polysporin).

  • Combination Products:

    • Examples include Cortisporin and Sofracort.

  • Labelling Importance:

    • It is essential that products are clearly labeled; otherwise, they cannot be interchanged between otic and ophthalmic uses.

Administration of Otic Drops

  • How to Instill Otic Drops:

    1. Shake the bottle as needed.

    2. Tilt the head so the affected ear is oriented upward.

    3. Pull the ear:

    • For adults: pull tip of ear up and back.

    • For children (≤ 3 years): pull ear lobe down and back.

    1. Place drops into the ear canal.

    2. Wait several minutes to allow drops to run into the ear.

PARTS OF THE HUMAN EYE

  • Key structures involved in ophthalmic preparations:

    • Eyelash

    • Pupil

    • Iris

    • Top Lid

    • Bottom Lid

    • Cornea (clear lens)

    • Sclera

    • Tear Duct

OPHTHALMIC PREPARATIONS

Conditions for Which Ophthalmic Preparations May Be Used

  • Infections:

    • Includes antibacterials such as:

    • Sodium Sulamyd

    • Garamycin

    • Ocuflox

    • Antivirals:

    • Example: Viroptic.

  • Glaucoma:

    • Treated with various medications, including beta-blockers.

  • Other Ophthalmic Drug Uses:

    • Eye Examination or Surgery:

    • Uses mydriatics (e.g., phenylephrine) and cycloplegics (e.g., cyclopentolate).

    • Inflammation:

    • Treated with anti-inflammatories such as steroids (e.g., prednisolone, dexamethasone).

    • Dry Eyes:

    • Lubricants like methylcellulose are used for relief.

OPHTHALMIC DOSAGE FORMS

  • Common forms include:

    • Ophthalmic Ointments

    • Solutions

    • Suspensions

    • Gels

    • Inserts

    • Example Product: Veterans Clean Treat Heal (FDA-Cleared Microcyn Technology) - An ophthalmic gel that kills bacteria in 30 seconds and provides relief from burning, stinging, and itching due to pollutants.

PROPERTIES OF OPHTHALMIC DOSAGE FORMS

  • Must ensure:

    • Sterility: Ensures that products are free from microorganisms.

    • Freedom from Foreign Particles:

    • Suspensions must contain microfine particles to avoid irritation.

    • pH Compatibility with the Eye:

    • Isotonicity:

    • Must be iso-osmotic with lacrimal fluid to prevent discomfort (0.9% sodium chloride solution).

    • Appropriate Viscosity:

    • Helps to prolong contact with the eye.

Terminology

  • Iso-osmotic: Two solutions with the same osmotic pressure.

  • Isotonic: Specifically refers to solutions that are iso-osmotic with body fluids such as tears and blood. Osmotic pressure equivalent to 0.9% sodium chloride (normal saline) is considered isotonic.

  • Hypotonic: Solution that has a lower osmotic pressure than the reference solution (body fluids).

  • Hypertonic: Solution that has a higher osmotic pressure than the reference solution.

Visual Representation of Tonicity

  • Hypotonic Solution:

    • Example: An animal cell submerged in a hypotonic solution will lyse (burst).

  • Isotonic Solution:

    • Example: An animal cell in an isotonic solution appears normal.

  • Hypertonic Solution:

    • Example: An animal cell in a hypertonic solution will shrivel.

Solutions for Ophthalmic Use or IV Injection

  • Both ophthalmic solutions and IV injections must be close to isotonicity with lacrimal fluids/blood.

  • This proximity to isotonicity helps prevent irritation to the eye and damage to blood cells.

PRESERVATIVES

  • Essential for all multi-use containers:

    • Single-use Containers:

    • Do not contain preservatives (e.g., Thera Tears lubricant eye drops).

    • Refrigeration:

    • Some solutions must be refrigerated if not preserved.

pH of Ophthalmic Preparations

  • Normal pH of Tears: 7.2 to 7.4

  • Tolerated pH Range by the Eye:

    • pH 6 to 8 for small volumes due to natural buffering action of tears.

  • Buffering Agents:

    • A mixture of a weak acid and its salt or a weak base and its salt can be used to maintain the desired pH.

Tonicity for Ophthalmic Preparations

  • Normal Osmotic Pressure of Tears:

    • Equivalent to 0.9% sodium chloride solution.

  • Tonicity Range Tolerance: 0.5% to 1.6% sodium chloride.

  • Hypertonic Solutions:

    • No adjustments can be made to remedy hypertonicity.

  • Hypotonic Solutions:

    • Can be made isotonic using boric acid or sodium chloride.

VISCOSITY in Ophthalmic Liquids

  • Thickening Agents:

    • Used to prolong contact time with the eye, such as:

    • Methylcellulose

    • Hydroxypropylmethylcellulose

    • Polyvinyl alcohol

PACKAGING AND STORAGE OF OPHTHALMIC PREPARATIONS

  • Ophthalmic Liquids:

    • Packaged in plastic bottles with built-in droppers, varying from 2.5 to 15 mL.

  • Ophthalmic Ointments:

    • Stored in metal or plastic tubes with a long narrow tip; typically supplied in 3 or 3.5 g amounts.

  • Solutions for Flushing the Eye:

    • Available in larger volumes (around 100 mL) and applied using an eye cup.

Administration of Ophthalmic Preparations

  • Ophthalmic Solutions:

    1. Lean back and gently pull down the lower lid to expose the pouch.

    2. Instill drops into the pouch.

    3. Close the eyes gently, applying pressure to the nose for about a minute.

    4. Discard after one month post-opening or if the solution appears cloudy or if used by someone else.

  • Ophthalmic Ointments:

    • Instill ointment (approximately 1.25 cm or ½ inch) into the pouch, then close the eye gently without applying nose pressure; note the potential for temporary blurred vision.

Knowledge Check

  • Which of the following conditions is commonly treated with ophthalmic preparations?

    • Options include Swimmer’s ear, Glaucoma, all eye injuries, and Stye (Hordeolum).

  • What is the correct order of instilling otic drops?

    • Correct Procedure:

    1. Shake the bottle.

    2. Pull the ear.

    3. Tilt the head (affected ear up).

    4. Instill the drops into the ear.

    5. Wait several seconds for the drops to settle.

  • True or False:

    • Some products can be used as both otic and ophthalmic solutions.