This is MCQ # 917 of 1000 Pharmacy MCQs

Pharmaceutical Calculation Problem solution


917. At a pharmacy, we have a vial that contains 5ml of lidocaine 1% solution. How many milligrams of lidocaine are present in 2ml of the solution?
a- 0.01 mg
b- 0.02 mg
c- 2.5 mg
d- 10 mg
e- 20 mg 

Solution:

As we know;

lidocaine 1% solution means 1gm or 1000mg of lidocaine are there in 100ml of solution

As we have a 5ml vial available at our pharmacy, we have to calculate first the milligrams of lidocaine present in 5 ml.

1000mg in 100ml
?mg in 5ml

cross multiplying, we get

1000mg x 5ml = ?mg x 100ml
5000 / 100 = ?mg

So, 50mg of lidocaine are there in 5ml solution.

Now let's calculate milligrams of lidocaine in 2ml solution.

50mg in 5ml
?mg in 2ml

again cross multiplying;

?mg x 5ml = 50mg x 2ml
?mg = 100 / 5 = 20

So 20 milligrams of lidocaine are there in 2ml solution.

Thus the correct answer is e.