Apoquel & Acute onset of severe, non-environmentally triggered compulsive Bx

Seeking input and information regarding following dog: Breed/Age/Sex: 6-year-old intact male German Shepherd Dog (GSD). Presenting Complaint: Acute onset of severe, non-environmentally triggered compulsive behaviors. Current Medication: Apoquel (oclacitinib) initiated recently for allergies History and Clinical Observation: The dog began exhibiting intense, persistent compulsive sniffing and digging behaviors shortly after starting the prescribed course of Apoquel. These behaviors are excessive, ritualistic, and appear to lack an identifiable environmental trigger (e.g., scent, buried item, anxiety stimulus). The intensity of these behaviors has resulted in the dog engaging in destructive actions to pursue them. Behavioral Assessment: There are no observable antecedent or consequence patterns that would typically explain such a rapid and severe onset of a new compulsive disorder. The behaviors are strongly correlated temporally with the initiation of the oclacitinib. Prior Veterinary Consult: The owner previously contacted their primary care veterinarian regarding this behavioral change. However, a potential connection to the medication was dismissed, no testing done either to assess or address owner concerns and no clear diagnostic direction was provided at that time. Action Taken & Request for Input: The owner has been formally instructed to schedule a comprehensive veterinary re-evaluation. We are seeking clinical experience or published/anecdotal reports from the veterinary community regarding a potential link between oclacitinib (Apoquel) and the acute development of neurological or obsessive-compulsive-related behaviors, specifically excessive sniffing and digging. Given the strong temporal correlation, there is concern regarding a rare adverse drug reaction potentially manifesting as a neurological or behavioral side effect. Any guidance on this specific adverse event or on appropriate diagnostic steps (e.g., ruling out organic/neurological pathology) would be highly appreciated prior to the client's next scheduled veterinary appointment.

Hello and thankyou for this fascinating case.  A lot of owners and clinicians read this page so I'll be interested to see whether anyone else picks this up.  If you go to the data-sheet for Apoquel (oclacitinib), you will see that convulsions are listed as one of the rarest side effects. Your dog sounds to have been awake and moving about while this was happening, but it is now being increasingly recognised that not all 'fitting' involves falling over and fully convulsing; there are repeated, involuntary motions that used to be called 'partial seizures;' it depends on where-abouts in the brain is affected.  Your vet would normally ask a lot of questions and carry out a basic neurological exam in order to try to distinguish the signs you report as being either neurological or behavioural.  I know of no obvious form of imaging or blood-test for this kind of neurological damage, which might explain why your vet has not done it; in some cases a brain scan might be useful - a neurologist is best to advise on that.   The drug company's own veterinary team may also be helpful; they should be able to tell you whether this has been reported before and I would expect them to openly do so.  However, I realise that they cannot be called 'impartial' and for this reason, if still unsure, would recommend seeking referral to a vet with a neurology specialism, to whom unusual neurological cases tend to be reported, in order to see what they can tell you.  I hope that something there is of help.