Rx: Codeine phosphate 30 mg/tsp Tussin syrup 30mL Elixophyllin qs 240 mL Sig: 5mL qid pc hs If 5 mL of Tussin syrup contains 100 mg of guaifenesin, how many milligrams of the drug would be taken daily?

50 mg.

Explanation:

From the prescription, 240 ml amount is to be prepared containing 30 ml tussin syrup. As the frequency is 5 mL qid, it means 5mL of syrup is to be administered four times daily i. e. 20 mL daily. To calculate the amount of tussin taken daily,

30 mL tussin = X mL of tussin

240 mL solution 20ml solution

⇒ 2.5 mL of tussin

5 ml tussin contains 100mg guafenesin,

So,

⇒ 2.5 ml of tussin contains 100x2.5/5 = 50 mg guaifenesin