Question

Adjust the isotonicity of the prescription written below using White – Vincent method and calculate the final quantity of NaCl for the isotonic solution that you have found.

Rx
Ciprofloxacin HCl 0,5 %       E = 0.23
Sodium sulphide 0.1 %       E = 0.31
Chlorbutanol 0.10 g     E = 0.10
Water   for injection       q.s. 15mL

Answer 1

ANSWER :-

Ciprofloxacin HCL (0.5%)

Amount that needs to be added in case if we consider NaCl = Weight of drug x E x amount of water

= 0.005 g/ml (0.5% which corresponds to 0.5g/100ml or 0.005 g/ml) x 0.23 x 15 ml

= 0.01725 g

Sodium sulphide (0.1%)

Amount that needs to be added = 0.001 g/ml x 0.31 x 15 ml

= 0.00465 g

Chlorbutanol (0.10 g)

Amount that needs to be added = 0.10 g x 0.10 x 15 ml

= 0.15 g

So, the total amount of sodium chloride which can be used as equivalent for the drug = Amount equivalent for Ciprofloxacin + Amount equivalent for Sodium sulphide + Amount equivalent for Chlorbutanol

= 0.01725 + 0.00465 + 0.15

= 0.21375 g

For NaCl, the amount that needs to be added = 30ml x 0.9% (0.009 g/ml) = 30 x 0.009

= 0.27 g

So, the amount of sodium chloride that needs to be added = Total amount of sodium chloride that needs to be added - Total amount of sodium chloride equivalent for the drug

= 0.27 g - 0.21375 g

= 0.05625 g of NaCl

This is the amount of NaCl that needs to be added for making the soution isotonic.