Pharmaceutics II 8.0 Ophthalmic and Otic

What are parts of the external eye?

- Eyelids

- Conjunctiva

What are the eyelids?

Mechanical barrier

What does reflexive blinking of the eyelids do?

Protect the eye with blinking assisting fluid movement

Conjunctival cul-de-sac

Lubricated and fluid-filled pockets

What is the conjunctiva?

The mucous membrane that lines the inner surface of the eyelids and covers cornea

What does the conjunctiva consist of?

- Superior conjunctival sac

- Inferior conjunctival sac

What are the purposes of Ophthalmic Dosage Forms?

1. Applied topically to treat (local) surface

2. Applied topically to treat intraocular conditions

Ointment

Regions 1-5

Drops

Regions 3-5

Subconjunctiva injection

5-6

Depp sub-tenons injection

6-8

Retrobulbar injection

8

What does the blood-retina barrier do?

Protect from back of the eye

Cornea

The window

What is corneal absorption?

(Diffusion via cornea) Is the major ophthalmic absorption route

What is the light like?

Transparent to light

How thick is it?

0.5 to 1 mm thick

What is the cornea like?

- Very sensitive nerve

- Nooo blood vessel

- Pre-corneal liquid film

- Laminar arrangement of cells and fibers

What are the layers of the cornea?

- Corneal epithelium

- Stroma

- Corneal endothelium

Corneal epithelium

Lipophilic: efficient bacterial barrier

Stroma

Hydrophilic

Corneal endothelium

Lipophilic (but less lipophilic than epithelium)

Precorneal liquid film has how many layers?

3 sub-layers:

Lipid

Tear

Mucus

Lipid

Thin oily outer layer

Tear

Thicker aqueous fluid middle layer

Mucus

Inner mucoid layer

When is the liquid film renewed?

When blinking

What is it compatible with?

Both aqueous and lipid pharmaceutical preparation

Most effective penetration for those drugs with?

Both lipophilic and hydrophilic properties

What is corneal absorption like?

Absorption o ionic molecules (e.g. a weak base)

How does it pass through cornea?

Free base (B) to cross epithelium--> Ion (BH+) to cross stroma--> Free base (B) to cross endothelium

How is the sterility in eyes maintained?

- Washing with fluids constantly

- Lysozyme and antibodies destroys some microorganism

What is lacrimal fluid like from the lacrimal gland?

- Aqueous, clear, pH about 7.4

- Protein and enzymes

- Organic compounds, glucose, salts

What are other lacrimal glands?

- COnjunctival accessory glands

- Sebaceous glands

What are sebaceous glands?

Excrete oily fluid to prevent overflowing tears

What is the tear volume like?

7 uL

Cul-de-sac without blinking

30 ul

Cul-de-sac after blinking

10 ul

Ophthalmic dispenser drop

50-75 ul

Topical administration volume limit

About 10 ul

Loss of instilled medication is?

Common

How does fluid movement occur in the lacrimal system?

Go to nasal cavity through nasolacrimal ducts

What is the lacrimal system like?

A dynamic fluid system for drug application

Drug retention on the eye surface is

Short: solution is flushed away in minutes

Only a portion of drug can be absorbed

<10%

Sterility by?

Autoclaving or filtration

Preservation for

Multiple dose preparation

Particle size of suspension

Less than 10 micrometer and stabilized

Ophthalmic suspension administration

Shake before use

Where are ocular inserts placed?

In the inferior cut-de-sac of the eye (under the lid)

Cleaning solutions

Contains nonionic or amphoteric (zwitterioninc) surfactants to dislodge mucus, lipids, and proteins

Wetting solutions

To lubricate and decrease surface tension of the lens

Soaking and storage solutions

Hydrate the lens on an aspect environment

The external ear

auricle, pinna, outer ear

The ear canal

external auditory passage

Tympanic membrane (eardrum)

Transmits the sound into the middle ear

What is the length of the ear canal?

About 1 inch in length

Skin lining

Very thin and tightly stretched

Where does the ear canal point for adults?

Downwards

How much can the adult ear canal hold?

About 0.85 ml (About 17 drops) of fluid

Ear canal and ceruminous glands

Secrete substances that form cerumen (earwax)

What does the glands do?

- Lubricates the lining of the ear canal

- Protects ear canal

- Aids the cleaning of debris

Earwax-softening agents

TO treat excessive/impacted earwax

How to hold earlobe for children age <3?

Downward and backward

How to hold earlobe for adults above 3?

Upward and backward