If that doesn't help, you may need to increase the Azith. dose to daily. Our dd was on 250mg daily when she was that size.
With PANDAS, it usually doesn't pay to be conservative with antibiotic dosing. To get improvement with antibiotics, it's important to use the "right" antibiotic (which can be trial and error, as some kids repond better to Azith, others Augmentin, etc) as well as a high enough dose.
You may eventually experiment with a lower dose but at least initially, the low doses often aren't effective.
IMO, PANDAS kids don't have a "good immune system against strep" which may be one reason lower doses don't seem to do much for them.
This is an update from my prior posting in March. DS8 had seen remarkable results with the lower dosage - all tics gone and OCD behavior gone, but socialization is still a big issue. HIs impulsiveness and ADHD behaviors have improved some, but continue to be a problem in the classroom. He is also verbally unkind to others to the point that he is loosing his best friend because of the hurtful comments he continues to make. Has anyone else seen that the tics and OCD behaviors improve before the behaviors. Do the behaviors eventually improve?
We went to a new doctor last week that was listed under treating physicians on pandas network.org. Dr. Bruce Russel in Port Aransas, TX. He was fantastic. The doctor increased the rx to 250 mg. of azithromycin daily instead of 500mg once per week. I am hoping that this will help with ADHD/impulsiveness behaviors.