The Student Room Group

Math dosing question

Question 19
A junior member of staff has just informed you of a medication error involving heparin. 25,000 units
was administered intravenously instead of 5000 units. The error is identified immediately and you
quickly discuss this with Pharmacy and the medical team who advise administering protamine
sulphate as an antidote using 1mg to neutralise every 100 units of heparin. If protamine sulphate
injection is available as 1% ampoules, how many mL are required to reverse the full 25,000 units of
heparin?

Answer: 25mL

My working out so far:
250mg covers 25,000 units.
I'm not sure what you do after this...don't know what 1% ampoules is supposed to tell us and how we change mg to mL to get 25mL.
(edited 8 months ago)
Reply 1
At a guess the 1% refers to 10mg/ml so youd need 25ml
Reply 2
Original post by mqb2766
At a guess the 1% refers to 10mg/ml so youd need 25ml

That makes sense but suppose we go by this logic then this involve you knowing what 1% means for all the different possible useable drugs. In this case it is 10mg/mL for Protamine sulphate - it could be a different amount for another drug.
(edited 8 months ago)
Reply 3
You're the medic, so this should be covered in your notes? The basic relationship of 1g of water corresponds to 1mL volume, so the measure may be related to that so 1% of xxx drug is 10mg per 1mL. But thats just a guess.

Original post by As.1997
That makes sense but suppose we go by this logic then wouldn't this involve you know what 1% means for all the different possible useable drugs? In this case it is 10mg/mL for Protamine sulphate - it could be a different amount for another drug.
(edited 8 months ago)
Reply 4
Original post by mqb2766
You're the medic, so this should be covered in your notes? The basic relationship of 1g of water corresponds to 1mL volume, so the measure may be related to that so 1% of xxx drug is 10mg per 1mL. But thats just a guess.

Soon, I should be able to give a better response once I've covered clinical pharmacology but it seems reasonable that we should be taught it, if a question can appear like this. That aside, my friend catch you another time! And as always your excellent math skills have helped me tremendously. Thanks man :smile:
Reply 5
Original post by As.1997
Soon, I should be able to give a better response once I've covered clinical pharmacology but it seems reasonable that we should be taught it, if a question can appear like this. That aside, my friend catch you another time! And as always your excellent math skills have helped me tremendously. Thanks man :smile:


NP. A quick google for 1% ampules seems to say something like 50mg/5mL or 10mg/1mL so it seems right, though Id not trust me in charge of drugs.
(edited 8 months ago)

Quick Reply

Latest