Pharmaceutics Exam 3 (Lecture 38- Compounding Otic Preparations)

Three types of Administration

• Local Delivery to eardrum

• Intratympanic (behind eardrum)

• Intracochlear (in cochlea)

Tympanic Membrane

• Separates Middle and outer ear

• Function: transmit sound waves

• Barrier for drug delivery to middle and inner ear (must be breached)

Three Layers of Tympanic Membrane

• Outer Epithelium

• Middle Fibrous Layer (collagen)

• Inner Mucosal

Blood-Perilymph Barrier (BPLB)

• Formed by capillary endothelium lining BV in cochlea

• Tight Junc./ No fenestrations

• Physical/Chemical barrier w/ efflux pump system

• Permeable to small liposoluble molecules

Round and Oval Windows

• Semi-permeable b/w cochlea and middle ear

• barrier to drug delivery to cochlea

Round window

Able to transport drugs from middle to inner ear (small & Big molecules)'

Benzyl Alcohol increase window permeability

3 layers of round window

1. Outer epithelium

2. Middle Connective Tissue

3. Inner Epithelium

Requirements for Otic Solutions

• Nonsterile, unless rupture eardrum

• Isotonic preferred

• pH: 3.5-7.5

• Viscosity: high so product retains in ear long enough from drug delivery

Solvents and Vehicles for Otic

• Glycerin, PEG, Propylene Glycol

• Viscous and act as preservatives in high concentrations

• Can use alcohol at max strength for topical use