Hi Mervyn,

Thanks for your question.

Unfortunately, I don’t give out recommendations about drugs, dosage and frequency of administering them. That is against my licensing and only the prescribing veterinarian can do that. I can tell you that the product you mention is given monthly as suggested by the manufacturer but a veterinarian can use it differently. It is applied to the skin and can be applied between the shoulder blades. Some veterinarians will recommend that you apply it down the middle of the back so it is deposited in small amounts in different locations, but if your veterinarian has given you the instruction you mention, please adhere to their direction.

The 20 refers to the dosage and I cannot provide advice on that issue.

Please ask this same question to the prescribing veterinarian to have it answered properly.

Thanks and all the best.

Dr. Greenway