- 1 Ocular
- 2 Otic
- 3 Dermatologic
The usual methods of applying medication directly to the eyes include liquid (drops) and ointments. The route and frequency of medication depend on the disease being treated. Liquids and ointments are appropriate for owner administration.
Liquid medications (usually 1 or 2 drops) can be applied directly to the cornea. It is important to instruct the owner on the proper technique and to stress that because liquids only fall downward, the patients nose must be directed upward before one attempts to administer liquid medications onto the eye. It is still quite difficult to encourage a drop of liquid, as it is squeezed from its container, to fall horizontally, despite frequent attempts to do so. Ointment, as a Vis- or !4-inch strip, is typically administered directly onto the sclera (dorsally) or into the lower conjunctival cul-de-sac such that as the lids close, a film of ointment is spread across the cornea.
The tip of the applicator tube for liquids and ointments should never be allowed to make contact with the eye or conjunctiva. Doing so is likely to result in contamination of the medication, especially with liquid medications.
Liquid solutions are more effective vehicles for administering medication into the external ear canal. Physically removing debris may be necessary in some patients that require topical otic medications. Occasionally, oral supplemental medication may also be required. When applying the medication, a few drops of liquid are generally sufficient. The ear should be massaged gently after instillation to facilitate the spread the medication within the external ear canal.
Medicated powders generally are contraindicated in the external ear canal. Also, the application tip of liquid medications must not come in direct contact with the skin. Doing so is likely to result in contamination of the entire dispensing bottle.
Intranasal administration of liquids in dogs and cats is usually limited to a single dose of a vaccine specifically labeled for intranasal administration. There is little indication for routine instillation of liquids into the nostrils of dogs and cats. Rarely, administration of isotonic solutions directly into the nostrils is indicated. In contrast to single-dose vaccines, lavage solutions applied intranasally are usually multiple-dose containers. Therefore the tip of the administration device should not be allowed to directly contact the patient’s skin or nose. Doing so may result in contamination of the entire bottle. Oily drops are not advised because they may damage the nasal mucosa or may be inhaled.
The technique for intranasal administration of vaccine is straightforward and usually works quite well… the first time. Some animals, dogs more than cats, will aggressively resist intranasal administration of vaccine. Attempts to overcome this resistance include covering the eyes with a towel or otherwise distracting the patient with noise or other visual cues.
Concerns expressed over the loss of vaccine immediately after intranasal administration are generally unfounded. Manufacturers of intranasal vaccines typically include a greater antigen (virus or bacteria) titer per dose than is necessary to induce a protective immune response. If the patient resists aggressively and the vaccine is indicated, parenteral preparations are available for all intranasal vaccines and should be considered.
Several objectives should be considered when treating dermatologic disorders with topical medication: (1) eradication of causative agents; (2) alleviation of symptoms, such as reduction of inflammation; (3) cleansing and debridement; (4) protection; (5) restoration of hydration; and (6) reduction of scaling and callus. Many different forms of skin medications are available, but the vehicle in which they are applied is a critical factor (Box Vehicles Used in the Administration of Topical Skin Medications).
Vehicles Used in the Administration of Topical Skin Medications
Lotions are suspensions of powder in water or alcohol. They are used for acute, eczematous lesions. Because they are less easily absorbed than creams and ointments, lotions need to be applied two to six times a day.
Pastes are mixtures of 20% to 50% powder in ointment. In general, they are thick, heavy, and difficult to use.
Creams are oil droplets dispersed in a continuous phase of water. Creams permit excellent percutaneous absorption of ingredients.
Ointments are water droplets dispersed in a continuous phase of oil. They are very good for dry, scaly eruptions.
Propylene glycol is a stable vehicle and spreads well. It allows good percutaneous absorption of added agents.
Adherent dressings are bases that dry quickly and stick to the lesion.
Shampoos are usually detergents designed to cleanse the skin. If shampoos are left in contact with the skin for a time, added medications may have specific antibacterial, antifungal, or antiparasitic effects.
In all cases, apply topical medications to a clean skin surface in a very thin film, because only the medication in contact with the skin is effective. In most cases, clipping hair from an affected area enhances the effect of medication. When dispensing medications to owners for home administration, the owner should be instructed to wear disposable examination gloves if using fingers and hands to apply the medication.
With the widespread availability of compounding pharmacies, prescribing compounded medications for topical and oral administration recently has become a popular dispensing technique for dogs and cats requiring long-term, daily medication. Caution is warranted. Some compounding pharmacies that serve the veterinary profession are using inappropriate or ineffective vehicles in which the drug has been compounded, or the drug itself, purchased in bulk, is of a lower grade and possibly an ineffective product once compounded. Studies on the quality and efficacy of compounded drugs for use in veterinary patients are limited. However, of those studies that have been performed, serious questions are being raised over the bio availability of the drug administered.