Question

You are babysitting your neighbor’s 16-month old daughter and you have to give her Mylicon® (simethicone) drops for gas. After looking at the label, you again find yourself thinking about your favorite class, Pharmacy Calculations. The label says that there are 20 mg of simethicone in every 0.3 mL of the drops. What is the percent strength (w/w)?

The specific gravity of the drops is 1.12.

Answer 1

20 mg Simethicone is 0.3ml of drops

Specific gravity of drop = 1.12

Specific gravity = Density of drop / Density of water

Density of drop = Specific gravity x Density of water

                       = 1.12 x 1000 = 1120

Density of drop = Mass of drop / Volume of drop

Volume = 0.3ml =0.3 x 10^-6 cubicmetre

Therefore Mass of drop = Density of drop x Volume of drop

                        =1120 x 0.3 x 1O^-6

                         =3.36 x 10^ -4 kg

                         =3.36x10^-4 x 10^3 g = 0.336g

0.3 ml drop contains 20 mg Simethicone

0.3ml drop weighs 336 mg =336 x 10^-3 g

Percentage weight by weight (w/w) means the number of grams of substance present in 100gram of preparation

Given 0.3 ml drop weighs 20mg simethecone = 20 x 10^-3 g

ie,336 x 10^-3 gram drop contains 20 x 10^-3 gram Simethicone

Therefore 1g drop contains 20/336 gram Simethicone

100g Drop contains (20 / 336) x 100 g Simethicone.= 5.95g of Simethicone.

Therefore the PERCENTAGE STRENGTH OF THE DROP IS 5.95(w/w)