by George J. Malmberg, RPh, FACA
Basic Information
Compounded ophthalmic-formulations for veterinary patients are used more often than ever before. Prepared in a dedicated cleanroom according to strict regulations for sterile compounds, their ingredients, strength, and dosage form can be individualized to treat the diseased or injured eye. Common ocular-diseases treated with compounded medications include:
- Canine keratoconjunctivitis
- Canine chronic superficial keratitis (pannus)
- Canine topic blepharoconjunctivitis
- Canine glaucoma
- Feline herpetic keratitis
- Conjunctivitis and viral ophthalmic conditions in a variety of species
- Equine keratomycosis
- Ocular manifestations of Bartonella henselae in cats
Although most compounds used to treat ophthalmic disease in veterinary patients are applied topically, compounded oral medications also are prescribed.
When to Prescribe Compounded Ophthalmic Medications
Veterinary practitioners diagnose and treat numerous ophthalmic conditions. More difficult cases usually are referred to a veterinary ophthalmologist for treatment. Most veterinary ophthalmologists are members of the American College of Veterinary Ophthalmologists or the American Society of Veterinary Ophthalmologists.
Compounded medications are prescribed when:
- The best therapy for a patient is not commercially available.
- The active drug ingredient is not available in the desired strength or dosage form.
- A commercial product is on extended backorder.
- A commercial product has been discontinued by the manufacturer for non-safety reasons.
- Patient/owner compliance may be improved and stress reduced through the use of pet-friendly flavoring and alternative dosage forms, resulting in better patient-outcomes.
- A new therapy reported in the veterinary literature is not available commercially.
- Special flavorings are required for oral medications.
- Dy- free or preservative-free topical formulations are necessary.
Effective Dosage-Forms
The most-common dosage forms for topical veterinary ophthalmic medications are solutions, suspensions, ointments, and gels. These dosage-forms are all within the capability of a knowledgeable compounding pharmacist with the appropriate equipment (discussed under Choosing a Compounding Pharmacy). Each dosage-form has unique formulation considerations.
Ophthalmic solutions are one of the most frequently used dosage-forms. Considerations when formulating a solution include solubility of the formula ingredients, clarity, tonicity, buffers, pH, sterility, and appropriate selection of preservatives when indicated. The most-common vehicle for solutions is water; however, there are oil solutions of select chemicals.
Ophthalmic suspensions generally are prescribed for medications that are not water-soluble. They usually are aqueous suspensions of the active ingredient. Particle size and the selection of a suspending agent are important when compounding an ophthalmic suspension. The particles in the suspensions must be small and uniformly suspended after shaking. Additional considerations are pH, sterility, and preservatives.
Ophthalmic ointments and gels are solid dosage-forms using either the more-common white-petrolatum vehicle or the newer aqueous methylcellulose gel. Compounding considerations for gels include ensuring a small, uniform particle size for a non-gritty, non-irritating product. Additionally, sterility and the selection of a preservative, if needed, must be considered.
All dosage-forms then must be packaged in an appropriate container. The packaging of veterinary ophthalmics must be sterile, protect the active drug, and facilitate administration. There are a number of options available including amber glass dropper-bottles or an opaque plastic drop-container to dispense solutions, and suspensions and tubes with ophthalmic applicator tips for ointments and gels.
Due Diligence Considerations
Not every pharmacy has the equipment, qualified staff, or facilities necessary to perform sterile compounding. The veterinarian who prescribes any preparation bears responsibility for the outcome of treatment and must exercise due diligence in selecting a compounding pharmacy. At a minimum, the pharmacy should have a Class 1000 cleanroom with a Class 100 Laminar Air Floor Hood or a Glovebox/Isolator to provide a sterile environment. This equipment should be certified independently biannually. Additional equipment such as sterilization filters, pH meters, micronizers, autoclaves, and ointment mills also are used by the pharmacist to prepare quality pharmaceutical-preparations.
Pharmacists should be familiar with veterinary compounding in general and veterinary ophthalmic compounding in particular. Compounding personnel should be trained and validated in aseptic technique according to USP guidelines. Quality-control evaluations that include weight, volume, pH, visual inspection, post-filtration integrity testing, and sterility testing should be performed on all batches of ophthalmic preparations. Documentation should be extensive and allow for the tracing of any dispensed medication back to the formulation worksheet and ingredient lot number. After the above criteria are met, other factors such as turnaround time and quality customer service, membership in professional organizations such as the American College of Veterinary Pharmacists and attendance at veterinary ophthalmology meetings also should be considered when a compounding pharmacy is selected to prepare ophthalmic preparations.
Compounded medications offer an excellent alternative for many ophthalmic patients.