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I am so confused about my Cats medication dosage! help? :)

post #1 of 2
Thread Starter 
Hi everyone! I am new to the forum, as are my cats Bonkers and Luna, along with my girlfriends Cats, Billie and Percy. My girlfriend has a problem with her old cat billie, he has hyperthyoridism and needs to take a medication called Methimazole. http://en.wikipedia.org/wiki/Methimazole

I am hoping you guys would feel bad either because we dont understand the math or just to help billie, and would offer advice we badly need!

She has a slip from her vet but it does not say how many syringes to buy. It only has dosages. Her vet and it seems most of our city does not carry the gel form, only the pill form. So she wants to order it from Dr. Foster's and Smith due to the fact it's a company based in our state. Here is their listing for the drug:


Here is where the problem comes into play.

The vet wrote the prescription like this:

Methimazole transdermal gel 50mg/ml (20mL)
0.05ml twice daily (2.5mg)

Note the confusing capital L in 20mL. Does ml = mL?

What does this translate into actual number of syringes?

The Dr.Fosters and Smith sell the 50mg/ml 1ml syringe, which seems to be what she needs. Yet on the phone in an effort to clear this up Dr. foster and smith tried to sell her $150ish worth of syringes!

Is this correct? We would hate to spend that and not be able to return it if its a mistake! (federal law,etc)

The best i could figure out is that each syringe has 20 doses, which means ONE syringe should be enough for 10 days.

Why? 0.05 x 2 = 0.10

0.10 x 10 - 1.00mg

Am i right? I have a nagging feeling i am wrong.

If anyone chooses to help I know she would feel so much better!

I think this post is ok in terms of the rules.. i am just asking for help on in essence math and dosage conversion. thank you for you time!!!!!!!!
post #2 of 2
It looks like each syringe contains 1 mL (the same as 1 ml--it stands for milliliters) of medication. Since the prescription is for 20 mL, you would need 20 syringes. You are right that each syringe would have 20 doses, or enough or 10 days. If you get 20 syringes (the maximum you could get with the prescription the vet wrote), you would have enough medicine for 200 days. I wouldn't recommend getting that many at once because some cats do react badly to the medication. You could start with 3 syringes, which would be a month's supply.

In case you are curious, the 50 mg/mL is the concentration--each mL of substance (basically each syringe) has 50 mg of medication. Since you are giving 0.05 mL of medication for each dose, you are giving 2.5 mg of medication (50 mg/mL * 0.05 mL=2.5 mg) in each dose.

I would also suggest buying either finger cots (http://en.wikipedia.org/wiki/Finger_cot) or gloves. The person administering the medication needs to make sure their fingers are covered so the medication isn't absorbed through their own skin.
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