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Dealing with Poor Response to Treatment

In general the dosage is unchanged throughout treatment, while the dose should be recalculated and adjusted as necessary on a weekly basis in response to weight changes.


However, in cases where a patient is not improving it may be necessary to raise the dosage of anti-viral. It is not appropriate to decrease the dosage of anti-viral as this increases the likelihood of resistance developing (an exception to this rule is when a cat is initially started on twice a day dosing or on a very high dose and then tapered to a lower frequency or dose within the first 3- 5 days).  


Dosages may need to be increased for the following reasons:

  • manifestation of neurological or ocular symptoms

  • lack of clinical improvement

  • lack of improvement in bloodwork

  • relapse of symptoms

In the case of effusions which are not resolving on the expected timeline, it is necessary to first eliminate other causes.

Before raising the dose it is recommended that you first confirm that the owner is administering the proper dose, and that the issue is not failure to inject or pill the cat.  Administration issues are common causes of treatment failure.


When increasing the dosage, it should be done in increments of:

  • 4-5 mg/kg (GS-441524 SC)

  • 4-5 mg/kg effective or 10 mg/kg actual (GS-441524 PO)

  • 10 mg/kg (GC376)

  • 4-5 mg/kg (Molnupiravir PO)

and if it elicits a positive response be continued for a minimum of 4 weeks.  This may mean increasing the length of treatment beyond 12 weeks.  

In the event of a relapse or major regression during treatment a minimum of 8 weeks from the point that dosage changes are made may be required.  This may require extending treatment beyond the usual 12 weeks.

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