Hard Chemistry Question

You are preparing an injection of a drug supplied as 5ml ampoules containing a solution at a concentration of 1mg/ml.
The required dose is 50mg/kg body weight and your patient weighs 80kg.
a) What volume of drug solution do you inject?

The answer is 4ml but i'm not sure how?
Concentration= 1mg in 1000ml
Required dose= 50mgx80--> 4000mg?

Reply 1

serendipity-

Original post by lindseyyy

Required dose is 4000mg but they want volume, which is measured in ml.
1ml = 1000mg. Therefore, it would be 4ml.

(edited 9 years ago)

Reply 2

username1445490

Original post by serendipity-

1ml = 1000mg. Therefore, it would be 4ml.

Where do you get this?
It is not a very well phrased question and

"containing a solution at a concentration of 1mg/ml." contradicts
"Concentration= 1mg in 1000ml"

If the rest of the question is correct then you need 4000 mg of drug for an 80 kg person.
If the concentration is 1mg/ml then that is 4L.
Something is not right.
To be 4ml volume or 4mg then the dose would have to be 50 µg/kg

Reply 3

serendipity-

Original post by Madasahatter

In general, isn't 1ml = 1000mg? I don't know, I just guessed this. The dose is 50mg/kg. That's the required dose.

Reply 4

username1445490

Original post by serendipity-

In general, isn't 1ml = 1000mg? I don't know, I just guessed this. The dose is 50mg/kg. That's the required dose.

Water in 1mg=1ml but this is a solution of a drug and we need (apparently) 4000mg of the drug not the solution unless the question is badly phrased and the dose is not 50mg/kg for the drug but 50mg/kg for the solution.
I say - bad question.

Reply 5

serendipity-

Original post by Madasahatter

Oh yes. I get what you mean. This is confusing. The question was most likely incorrectly phrased.

Reply 6

Dylann

Original post by serendipity-

In general, isn't 1ml = 1000mg? I don't know, I just guessed this. The dose is 50mg/kg. That's the required dose.

That's only for water, where everything is nice and easy. 1g=1cm3=1ml

This is because of its density, 1g/cm3.

It changes with other substances

Edit: notice though that 1cm3 will always be 1ml regardless of chemical as it measures space being occupied rather than chemical mass

Posted from TSR Mobile

(edited 9 years ago)

Reply 7

serendipity-

Original post by Dylann

Ohh. Thanks for explaining :smile:

Reply 8

lindseyyy

Original post by Madasahatter

So does "concentration of 1mg/ml" not mean 1mg in 1000ml? Does it meal 1mg for every 1ml?

Thanks!

Reply 9

username1445490

Original post by lindseyyy

So does "concentration of 1mg/ml" not mean 1mg in 1000ml? Does it meal 1mg for every 1ml?

Thanks!

Yes 1mg/ml is 1mg per ml so every ml contains 1mg.

Reply 10

lindseyyy

Original post by Madasahatter

Yes 1mg/ml is 1mg per ml so every ml contains 1mg.

So this is the original question:

You are preparing an injection of a drug supplied as 5ml ampoules containing a solution at a concentration of 1mg/ml.
The required dose is 50mg/kg body weight and your patient weighs 80kg.
a) What volume of drug solution do you inject?

Does that mean that the answer of 4ml is wrong? because surely if the patient weighs 80kg, 80kg per mg= 4000mg are needed by the patient?

And therefore if 1mg=1ml then 4000ml are needed, not 4ml?

So confused!

Reply 11

username1445490

It does seem that there is something not correct with the question!