Question

2. What is the volume of sterile purified water and 0.9% w/v sodium chloride solution needed to prepare 30 mL of a 2% w/v solution of tobramycin for ophthalmic use? • Step 1: Calculate the tonic contribution provided by the tobramycin (FDP 1% tobramycin = 0.04°C) Step 2: Calculate the amount of NaCl necessary to render this product isotonic Step 3: Your source of NaCl is 0.9% NaCl. What volume of the 0.9% NaCl solution will yield the calculated amount of NaCl? 3. Calculate the amount of sodium chloride needed to properly compound the following prescription Dipivefrin HCI Sodium Chloride Purified water 0.3g q.s. isotonic qs ad 50 ml Sig: i gtt into each eye twice daily

Answer 1

Question 2.

Step 1. The weight of tobramycin = (2 g/100 mL)*30 mL = 0.6 g

Step 2. The NaCl equivalent of tobramycin = 0.6*0.07 = 0.042 g (E-value of tobramycin = 0.07)

Step 3. (0.9/100) * V = 0.042 g

i.e. The volume of 0.9% w/v NaCl (V) = 4.67 mL

Question 3.

The NaCl equivalent of Dipivefrin HCl = 0.3 g * 0.15 = 0.045 g ((E-value of Dipivefrin HCl = 0.15)

The actual amount of NaCl required = (0.9 g/100 mL)*50 mL = 0.45 g

Therefore, the amount of NaCl required to make the given solutino isotonic = 0.45 - 0.045 = 0.405 g