Secondary infections can be the biggest confounding factor when interpreting diet trials. For example:
• Did the patient have a flare of pruritus when stopping their medication because they do not have a food allergy, or did a secondary pyoderma develop that is causing pruritus instead?
• Did the patient remain in remission when stopping their medication because they are food allergic, or is otitis their only clinical sign, which can take a long time to progress from a mild yeast otitis that might go unnoticed to a more evident and severe Pseudomonas otitis with pain and a purulent exudate?
When performing a diet trial, regular examinations by the VS or VN can be helpful to make sure that everything is going to plan and there are no signs of infection. An examination at the start of the trial is necessary to ensure that the patient is either rapidly clinically improving or already in remission. A midway( 4-week) examination should be performed to make sure they are now( or are still) in remission before stopping their medications. An end-point examination is then needed to make sure they have not relapsed, before moving on to the re-challenge( provocation) phase.
Antipruritic medications
Choosing the right antipruritic medication is also vital. Factors for the VS to take into consideration when choosing what to prescribe are efficacy, duration of action, the need for tapering and various other pharmacological aspects( Table 3) [ 9 – 11 ].
Table 3. Antipruritic medications and their advantages and disadvantages [ 9 – 11 ].
Medication Advantages Disadvantages Comments Oral corticosteroids • Cheap
• Effective
• Quick onset of action
Injectable steroids • Helpful for patients that cannot be medicated orally
• Can cause unmanageable side effects
• Cannot be stopped without tapering to physiological doses
• Difficult to judge duration of action
• Difficult to time administration appropriately for the stage of the diet trial
• Can cause side effects
• Risk of diabetes is increased with certain injectable steroids when repeatedly administered
Janus kinase( JAK) inhibitors, e. g. oclacitinib( Apoquel, Zoetis), ilunocitinib( Zenrelia, Elanco), atinvicitinib( Numelvi; MSD Animal Health) |
• Effective in many cases
• Rapidly absorbed and highly bioavailable [ 9 ]
• Non-flavoured options available
|
• Not effective in all cases
• Long-term use requires haematological monitoring
• More expensive than steroids
|
• No need to taper before stopping
• Avoid the flavoured version
• Not licensed for cats
|
Ciclosporin • Capsules or liquid • More expensive than oclacitinib and steroids
Lokivetmab • Injectable
• Minimal side effects
• Takes 4 – 6 weeks to reach maximal effect
• Antipruritic but not antiinflammatory
• Not always effective in the face of secondary infection
• Dogs that do not respond well to JAK inhibitors will be unlikely to respond to lokivetmab [ 11 ]
• Not ideal for use during a diet trial due to long induction and reduction periods [ 10 ]
• More useful for patients that are well managed as a way of de-escalating to the lowest-potency medication
• Caninised monoclonal antibody – not suitable for use in cats
42 Veterinary Nursing Journal