PF1011 Calculations PDF

PF1011 – Calculations Dr Kevin Murphy [email protected] Aim/Objectives Competently perform: Conversion between units and measurement systems Basic dosage calculations Calculations for basic compounding Peppermint water case Pepperm...

PF1011 – Calculations Dr Kevin Murphy [email protected] Aim/Objectives Competently perform: Conversion between units and measurement systems Basic dosage calculations Calculations for basic compounding Peppermint water case Peppermint Water Peppermint emulsion 3.75ml Chloroform water, double-strength 75 ml Purified water up to 150 ml Chloroform water concentrations Chloroform water, single-strength 0.25% Chloroform water, double-strength 0.5 % Chloroform water, concentrated 10 % Recommended textbook Understanding prescription shorthand writing More prevalent in the past Aided speedier prescription writing Based on English and Latin words Common ones only for these sessions Taken from Farmer's Pharmacy - International Rotation Rx shorthand - General Term Meaning Derivation ℞/Rx/Rx The Recipe (to receive) prescription Sig. Label Signa (to write on a label) Mitte Total Mitte (send/give) quantity Rx shorthand - Frequency Term Meaning Derivation bd/BD Twice a day bis dei bid/BID Twice a day bis in dei mane in the morning mane nocte at night nocte od/OD once a day omni die prn/PRN when required pro re nata q6h every 6 hours quaque 6 hora qds/QDS four times a day quarter die sumendus qid/QID four times a day quarter in die tds/TDS three times a day ter die sumendus tid/TID three times a day ter in dei tarde in the evening tarde Rx shorthand - Duration/Route Term Meaning x 5/7 For 5 days x 4/52 For 4 weeks Repeat x 2/12 Repeat for 2 more months Rx2 repeat twice Term Meaning PO Orally SC s/c Subcutaneously IV Intravenously IM Intramuscularly Pharmaceutical Calculation Basics - Prefixes Prefixes and symbols for subdivisions and multiples of SI units Prefix: Symbol: Magnitude: Multiply by Tera- T 1012 1 000 000 000 000 Giga- G 109 1 000 000 000 Mega- M 106 1 000 000 kilo- k 103 1000 hecto- h 102 100 deka- da 10 10 15 mcg NOT deci- centi- d c 10-1 10-2 0.1 0.01 15 µg milli- m 10-3 0.001 micro- µ/mc 10-6 0.000 001 nano- n 10-9 0.000 000 001 Example of potential error Pharmaceutical Calculation Basics - Imperial Imperial units and their SI equivalents Mass 1 ounce (oz) 28.35 g 1 pound (lb) 453.59 g 1 stone (st) 6.35 kg Volume 1 teaspoon (tsp) 5 mL 1 tablespoon (tbsp) 15 mL 1 pint 568 mL Length 1 inch (in) 2.54 cm 1 foot (ft) 30.5 cm Pharmaceutical Calculation Basics - Concentrations Pharmaceutical Calculation Basics - Performing Writing Always write the 0 before the decimal place! ALWAYS 0.5 mg NEVER.5 mg Always omit decimal points from whole numbers! ALWAYS 1 mg NEVER 1.0 mg Always group zeros in 3s using a comma ALWAYS 100,000 units NEVER 100000 units Always include units in every line of your calculations Rounding If the figure one place beyond the required number of figures is ‘5’ or more then add 1. If the figure one place beyond the required number of figures is less than 5 add zero. Pharmaceutical Calculation Basics - Performing Calculators Perform calculations without a calculator Then perform them with a calculator Approximation Finally, check if the answer makes sense Will the quantity have no therapeutic effect or kill the patient? (e.g. paracetamol 1mg qds instead of 1g qds) Is the quantity impractical? (e.g. 100L injection) Colleagues If unfamiliar with a calculation, ask a colleague to also perform it and compare answers Session 1 Calculations Type vevox.com into your browser Enter the following room number: 116-004-012 Or Click the link below: https://vevox.app/#/m/116004012 Question 1 Calculate the Body Mass Index (BMI) of the patient below: Patient height: 5 foot 4 inches Patient weight: 10 stone and 11 pounds The answer should be rounded to one decimal place. Question 2 If a medication had 2 parts Drug X to 8 parts excipient, what percentage of the medication is Drug X? Question 3 You are the presented with the following prescription: Ramipril 5 mg OD x 1/12 Repeat x 2 How many months of ramipril is the patient entitled to? Question 4 A patient with a respiratory infection presents the following prescription: Amoxicillin 250 mg 2 caps TID x 5/7 Prednisolone 5mg 4 tabs BD x 1/52 Will you dispense a greater number of tablets or capsules?