Hello, I'm Dr. Deb.
I recently came online and see that your question about Max hasn't been answered. I'm so sorry that you've had to wait for a response, but if you still need assistance, I'd like to help if I can.
I believe you should be able to purchase Ivomec (aka Ivermectin) online
(http://www.amazon.com/Ivomec-Injection-1-50ml-Btl/dp/B0002APD1Y) without a prescription. In fact, this particular product may be available at some feed or grain stores.
Although the label indicates it's for cattle and swine, it's used off-label by many vets for treatment of many parasites, including nasal mites.
When used at extra-label dosages in dogs, ivermectin should not be used in breeds susceptible (Collies
, Shelties, Australian shepherds
, etc.) to the ABCB1-1Δmutation unless the patient has been tested and found not to have the gene defect. Having said that, ShihTzu's are not among those considered at risk for having this gene mutation.
The dose I use for nasal mite treatment for my patients would be 0.3 mg/kg orally or under the skin as an injection every 1-2 weeks for 2-3 treatments. The taste is rather bitter, however, so it can be mixed with a little tuna or clam juice which may help to make it more palatable.
For example, if I were treating a 20 lb dog, my dose of Ivomec would be 0.3 cc's at one time. (Note that the concentration of the product must be taken into account when figuring out the correct dosage).
I hope this helps although my apologies for the delayed reply. Deb