Ophthalmic and Otic Medications: Pharmacology and Administration

Brand name for diphenhydramine

Benadryl

Brand names for hydroxyzine

Vistaril, Atarax

Brand name for meclizine

Antivert

Brand name for cetirizine

Zyrtec

Brand name for fexofenadine

Allegra

Brand name for loratadine

Claritin

Brand name for fluticasone

Flonase

Brand name for mometasone

Nasonex

Brand name for oxymetazoline

Afrin

Brand name for pseudoephedrine

Sudafed

Routes of ophthalmic drug absorption

1. Transcorneal (penetration through cornea into anterior chamber)

2. Conjunctival and scleral (local uptake into conjunctival and scleral tissues)

3. Nasolacrimal (drainage through nasolacrimal duct into the nasal mucosal epithelium)

Ophthalmic absorption pathway responsible for the greatest systemic absorption

The nasolacrimal route (leads to nasal mucosal absorption)

Why nasal mucosal absorption is responsible for greatest systemic absorption:

-The nasal mucosa is lined with highly vascularized epithelium, allowing direct entry into systemic circulation

-Bypasses hepatic first-pass metabolism (in the liver)

Clinical use of ocular antibacterial agents

Treatment of superficial and bacterial infections of the eye and surrounding ocular structures

(conjunctivitis, blepharitis, keratitis)

Clinical use of ocular antiviral agents

Treatment of viral ocular infections.

(herpes simplex keratitis, herpes zoster ophthalmicus, CMV retinitis)

Clinical use of ocular antifungal agents

Treatment of fungal infections of the eye

(fungal keratitis, fungal endophthalmitis)

Clinical use of ophthalmic antiprotozoal agents

Treatment of parasitic infections of the eye, specifically Acanthamoeba keratitis

Artificial tears

Non-medicated products formulated to mimic natural tears

Therapeutic use of artificial tears

-Provides ocular surface lubrication

-Relieves irritation or discomfort caused by dry eye/ inadequate tear production

Ophthalmic beta-adrenergic blockers MOA

Block beta receptors in the ciliary epithelium to decrease aqueous humor production and lower IOP

Ophthalmic Miotics MOA

Induce pupillary constriction (miosis) and ciliary muscle contraction, to enchance aqueous humor outflow through the trabecular meshwork and lower IOP

Ophthalmic Carbonic anhydrase inhibitors MOA

Inhibit a specific enzyme in the ciliary body, resulting in decreased secretion of aqueous humor and reduced IOP

Prostaglandin agonists MOA

Lower intraocular pressure (IOP) by increasing the uveoscleral outflow of aqueous humor

Antihistamines MOA

Competitively block local histamine receptors to relieve ocular itching and redness

Mast cell stabilizers MOA

Prevent mast cell degranulation and pro-inflammatory mediator release in allergic conjunctivitis

Ophthalmic vasoconstrictors/ decongestant warnings

1. Use caution in patients with hypertension or cardiovascular disease (systemic absorption)

2. Most are contraindicated in narrow-angle glaucoma (if they produce pupillary dilation/ mydriasis)

Ophthalmic vasoconstrictors/ decongestant MOA

Alpha-adrenergic agonists that stimulate alpha receptors on conjunctival vessels to induce vasoconstriction and reduce redness

Ophthalmic NSAIDs MOA

Inhibit the cyclooxygenase (COX) enzyme and decrease prostaglandin synthesis

(manage postoperative pain, inflammation, and allergic conjunctivitis symptoms)

Ophthalmic corticosteroids MOA

Provides broad local anti-inflammatory activity to suppress ocular inflammation, swelling, and irritation

Proper administration steps for eye drops

1. Shake suspension formulations prior to instillation

2. Pull down the lower eyelid to create a pocket

3. Instill $1$ drop without touching the dropper tip

4. Close the eye for $1\text{ to }3\text{ minutes}$ while applying gentle pressure to the tear duct and avoid excessive blinking

5. Wait at least $5\text{ minutes}$ between different eye drops

Administration technique and key patient

1. Instill a $\frac{1}{4}\text{ to }\frac{1}{2}\text{ inch}$ ribbon across the pocket formed by the lower eyelid

2. Close eyes gently for $1\text{ to }2\text{ minutes}$

3. Wait $10\text{ minutes}$ between ointments.

Eye ointments

Counseling point: Transient blurry vision due to viscosity makes bedtime application ideal

Proper preparation and administration technique for otic drops

1. Warm the bottle in hand for $1\text{ to }2\text{ minutes}$ to body temperature to minimize dizziness and pain

2. Shake suspensions for $10\text{ seconds}$

3. Tilt the head with the affected ear facing upward, instill drops, and maintain the tilted position for several minutes

4. Never insert cotton swabs or foreign objects into the canal

Pinna alignment for administering ear drops to adults/ children over 3 years

Pull the pinna upward and backward

Pinna alignment for administering ear drops to children younger than 3 years

Pull the pinna downward and backward

Topical otic medications

Medications remain localized in the EAC with minimal systemic absorption since they cannot cross an intact tympanic membrane; are typically not effective treatments for middle and inner ear infections.

Clinical use of otic antibiotics

Treatment of bacterial infections localized to EAC, such as acute otitis externa.

Clinical use of otic corticosteroids

Reduction of inflammation, pruritus (itching), and edema in the EAC

Clinical use of otic ceruminolytics

Soften, loosen, and break up cerumen (earwax) buildup to facilitate safe ear canal cleansing. Contraindicated if the tympanic membrane is perforated.

Cinical use of otic drying agents

Dislodge trapped water and evaporate moisture from the EAC by breaking surface tension, helping to prevent or manage swimmer's ear (otitis externa).