Medication Calculations - University of Southern Queensland

1 Medication CalculationsBefore you begin to perform Medication Calculations , it is important that you reviewyour knowledge on basic maths Calculations , such as fractions, percentages, ratios anddecimals. The following examples explain the formula and the ratio method of medica-tion formula for the calculation of a Medication to be administered:Volume or Strength Required=Strength RequiredStock Strength or Stock Available Stock is the difference between ratios and proportions?Ratiois a comparison of two or more related quantities. Ratio is represented by a example 2 : 3 .Proportionis part of a whole. Proportions are represented as fractions or decimals.

2 Forexample,12= .Note: When administering tablets orally, the stock volume is always 1, since tablets arein their solid form. Units for the strength required and stock strength must be the 1 The doctor ordered 150 mg of Aspirin for your patient. Aspirin is available as 300 mgper tablet. How many tablets would you administer to your patient?Solution:Using the formula methodStrength required=150 in stock= 300 mg per of tablets=150 mg300 mg per tablet 11=12of a tablet .The ratio methodThe steps to follow are1. Write what you know or what is available as a ratio. For example, 300 mg : 1 tab .2. Write the doctor s order and the unknown as a ratio.

3 For example, 150 mg :xtab .Use letterxfor the Write ratios as fractions and cross multiply to solve mg : 1 tablet ,150 mg :xtablet .Write as fraction:300 mg1 tablet=150 multiply to give3001=150x300x=150 .Dividing both sides by 300 to solve forx 300x 300=150300x=12tablet .Example 2A patient is prescribed 240 mg of Gentamycin, and the stock strength is 80 mg per 2 the volume of Gentamicin :Using the formula methodVolume Required=240 mg80 mg 21mL=6 mL of Gentamycin .Using the ratio methodStock strength: 80 mg : 2 mL ,Doctor s order: 240 mg :xmL .Write as fraction80 mg2 mL=240 mgxmLCross multiply to give802=240x80x=480.

4 Dividing both sides by 80 to getx 80x 80=48080x=6 mL .Therefore, the volume of Gentamycin needed is 6 resources Brotto and Rafferty (2016) Reid-Searl, Dwyer, Moxham, and Reid-Speirs (2007) Online resources at Study Support; Arrange a consultation with a Mathematics Learning , V., & Rafferty, K. (2016).Clinical dosage Calculations for Australia and New Zealand(2nd ed.). South Melbourne, Australia: Cengage , K., Dwyer, T., Moxham, L., & Reid-Speirs, J. (2007).Nursing student s maths& medications survival guide. Frenchs Forest, Australia: Pearson.