Question

How many milliliters o a suspension base must be mixed with 250 mL o a paroxetine (PAXIL) oral suspension, 10 mg/5 mL, to change its concentration to 0.1% w/v?'

Answer 1

Answer : The suspension base added will be, 250 mL

Explanation :

As we are given that the initial concentration of solution is, 10 mg/5mL or we can say that 2 mg/mL.

Volume of solution = 250 mL

First we have to determine the mass of PAXIL.

As, 1 mL of solution contain mass of PAXIL = 2 mg

So, 250 mL of solution contain mass of PAXIL = $250\times 2=500mg$

Now we have to determine the final solution required.

As we are given the final concentration of solution is, 0.1 % w/v that means 0.1 g in 100 mL of solution.

Concentration of solution = $\frac{0.1g}{100mL}=\frac{0.1\times 1000mg}{100mL}=\frac{100mg}{100mL}=\frac{1mg}{mL}$

Let the 'x' mL of the suspension base is added. So, the ratio of mass and volume will be:

$\frac{500mg}{(x+250)mL}=\frac{1mg}{1mL}$

$x=250mL$

Thus, the suspension base added will be, 250 mL