Just Ask the Expert: What frequency of immunotherapy works for your patients?
Dr. Spiegel welcomes dermatology questions from veterinarians and veterinary technicians.
Intradermal testing and allergen-specific immunotherapy have worked well for my patients. I know that some veterinarians have clients give the hyposensitization vaccine every three weeks, some have clients give it every two weeks, and some have clients give it every week. In my experience, clients too often forget to administer the vaccine with the three-week regimen, and some also forget with the two-week regimen. Consequently, I have my clients give injections every week. What do you prescribe? Do you find a weekly regimen acceptable, or is it too frequent?
A. Numerous desensitization regimens are proposed for veterinary patients, but no specific schedule is necessarily better than the others are.
You also must consider the volume of allergen administered. I usually try to attain a maximum dose of 1 ml of allergen, but that does not apply to all my patients. If a patient has trouble tolerating this dose, I may decrease the volume and not necessarily alter the administration frequency.
I tend to have the client administer 1 ml (20,000 PNU/ml) every week for two or three months, and then I alter the frequency to every 10 to 14 days. My goal is usually to gradually decrease the frequency of injections to every three or four weeks for long-term cases (by the time a patient has had eight to 12 months of immunotherapy).
The administration frequency can also be adjusted based on how a patient responds. I often have a client adjust the administration schedule to every seven to 10 days during certain seasons and then back to every three weeks at other times of the year. This seasonal frequency adjustment often seems helpful.
I am fine with a weekly regimen, but I would administer a lower volume (e.g. 0.5-ml dose) to keep the expense of immunotherapy from increasing substantially. For example, if you have a two-vial set, 0.5 ml of each vial once a week would be a reasonable approach for some patients. I find, however, that my clients are usually excited about decreasing the administration frequency.
Although there is no particular schedule for immunotherapy, it is best to choose a schedule and use it as a guideline. I find that success with allergen-specific immunotherapy requires constant observation and adjustments, along with choosing the right patient. This means choosing a candidate with the right temperament for injections and choosing a patient that is more likely to respond. In my opinion, patients that have been chronically affected (all-year-around) for more than five or six years or patients over 10 to 12 years of age are less likely to respond. This does not mean immunotherapy cannot be a component of treatment, but this option is less likely to be effective as a sole therapy.
Ian Spiegel, VMD, MHS, DACVD