I think the answer for PTCB Practice Test 12 Question #4 may be incorrect. Here is the question:
A patient with ulcerative colitis has been ordered the following prescription:
Rx: Prednisolone Syrup 0.30% Sig:15mg qd ac X7 days.
What will the dosage instructions be on the patients packaging?
A. Take 2 Teaspoons daily before a meal. B. Take 1 Tablespoon daily before a meal. C. Take 2 Tablespoons daily before a meal. D. Take 1 Teaspoon daily before a meal.
The answer Says D, but 15 mg = 1 tablespoon and 1 tsp is 5 mg. So the answer should be B... I believe? Correct me if I'm wrong. Thanks!
Reply: By Jerry
Firstly, 1 tsp is MUCH more that 5 mg. Since you're probably familiar with sugar, let's use that for an example. 1 tsp of sugar is over 4000mg. The confusion starts when we learn to mix things using teaspoons and tablespoons in cooking recipes, because it's easier than weighting things like sugar while making cookies. Imagine if a cake recipe told you to add 250,000 mg of sugar. Adding 1 cup is lots easier, right?
So, the mistake you're making is common, and one that new pharm tech students often make when getting started with the math.
You are confusing liquid and dry measurements. When doing pharmacy math - Always use volume measurements (mL, quart, Liquid ounce, Tablespoon, Teaspoon) for liquid and weight measurements (mg, Kg, Ounce, Lb) for solid and dry substances.
This question involves a concentration of a substance in a liquid, which is prepared as 0.3%. So, we know that there are 300mg in every 100mL.
So, we need to find out how many mL will contain 15mg. This is done most quickly with a proportions math equation like this: