Dosing and calculations

Question 1

what are 6 medications that can cause serious harm in calculation error?

Answer 1

APINCH

Antimicrobials
Potassium and electrolytes
Insulin
Narcotics
Chemotherapy
Heparin and anticoagulants

Question 2

what are 3 cautions needed when administering insulin?

Answer 2

only use insulin syringe - scale in units rather than ml
do not withdraw insulin from insulin pen or refill cartilage
Write units in full for insulin

Question 3

why are children vulnerable to dosing and calculation errors?

Answer 3

small dose errors have more of an effect on a child
doses need to be calculated on weight - individualised dosing
liquids vary in strengths
confusion between ml and mg dosing
non-licensed preparations

Question 4

what is the ideal body weight?

Answer 4

used to calculate dose of water soluble medications (e.g. gentamicin) to avoid obese people being overdosed

Question 5

what is the general formula for lean body weight?

Answer 5

LBW = actual body weight - body fat weight

Question 6

what are 4 ways to estimate paediatric weight in an emergency?

Answer 6

body length - broselow emergency paediatrics tape
Age - paediatric emergency drug chart
Weight = (age + 4) x2 - up to 10 years

Question 7

concentration =

Answer 7

mass/volume

Question 8

what is a weight/weight percentage?

Answer 8

weight of active ingredient in 100g of medication

e.g. 0.5% cream = 0.5g in 100g of cream

Question 9

what is weight/volume percentage?

Answer 9

weight of medication in 100ml of solution

0.9% saline = 0.9g of NaCl in 100ml of solution

Question 10

what is volume/volume percentage?

Answer 10

ml of liquid medicine in 100ml of final product

Question 11

How many lb in a stone?

Answer 11

14 pounds

Question 12

how many grams in 1lb?

Answer 12

450g in 1lb

Question 13

how many kg in one stone?

Answer 13

6.35kg in one stone

Question 14

how many inches in a foot?

Answer 14

12 inches

Question 15

how many mm in 1 inch?

Answer 15

25.4mm in 1 inch

Question 16

what is 1 foot in mm?

Answer 16

1 foot = 304.8mm

Question 17

what is the usual conversion between oral codeine and oral morphine?

Answer 17

codeine is 10x weaker than morphine orally

Question 18

what is the usual conversion from oral to SC/IV morphine?

Answer 18

Oral morphine is half as potent as SC/IV

Question 19

what is the conversion from SC/IV diamorphine to oral morphine?

Answer 19

SC/IV diamorphine 3x stronger than oral morphine

Question 20

what is the opioid dosing for breakthrough pain?

Answer 20

1/10th to 1/6th the daily dose

Question 21

what is the equivalent dose of chlordiazepoxide to 5mg diazepam?

Answer 21

12.5mg chlordiazepoxide

Question 22

where can benzodiazepine dose equivalents to diazepam be found in the BNF?

Answer 22

hypnotics and anxiolytics treatment summary

Question 23

where can you find dose conversions for steroids compared to 5mg of prednisolone in the BNF?

Answer 23

glucocorticoid therapy treatment summary

Question 24

what is the conversion for 5mg of pred to dexamethasone based on glucocorticoid activity?

Answer 24

750micrograms dex for 5mg pred

Question 25

how to calculate volume of parenteral medicine?

Answer 25

volume required = (dose X volume of solution)/amount of medicine in solution