DOSING AND CALCULATIONS

Question 1

what are the high risk medications for making calculation errors?

Answer 1

A-PINCH
A - antimicrobials
P - potassium and electrolytes
I - insulin
N - narcotics
C - chemotherapy
H - heparin and anticoagulants

Question 2

how can you avoid calculation errors with insulin?

Answer 2

Only use insulin syringes to withdraw insulin from vial
Always write units in full (do not abbreviate)

Question 3

what standard of practice is in place to check drug calculations?

Answer 3

independent second checks

Question 4

what are the conversion factors between different weight measurements?

Answer 4

Question 5

what does %weight/weight (%w/w) mean?

Answer 5

In 1% w/w preparation there is 1g of medicine in 100g of final product

Example hydrocortisone 0.5% w/w
0.5g of hydrocortisone in 100g of cream

Question 6

what does %weight/volume (%w/v) mean?

Answer 6

In 1% preparation there is 1g of medicine in 100ml of final product

Example sodium chloride 0.9% w/v
0.9g sodium chloride in 100ml of infusion

Question 7

what does %volume/volume (%v/v) mean?

Answer 7

In a 1% v/v solution there is 1ml of liquid medicine in 100ml of final product

Question 8

how do you interpret ratios of medications?

Answer 8

1:1000 means 1g in 1000ml
1:100000 means 1g in 100000ml

Question 9

what are some basic weight conversions?

Answer 9

1 stone = 14lbs
1lb = 450g
1 stone = 6.35kg

Question 10

what are some height conversions?

Answer 10

1 foot = 12 inches
1 inch = 25.4mm
1 foot = 304.8mm

Question 11

where would you find the BNF conversion chart for opioids?

Answer 11

prescribing in palliative care

Question 12

what dose of opioid would you provide for breakthrough pain?

Answer 12

1/10-1/6 of the total daily dose

Question 13

where would you find the BNF conversion chart for benzodiazepines?

Answer 13

hypnotics and anxiolytics

Question 14

where would you find the BNF conversion table for corticosteroids?

Answer 14

glucocorticoid therapy

Question 15

how do you calculate the infusion rate?

Answer 15

rate = volume / time

Question 16

how do you calculate concentrations?

Answer 16

concentration = mass / volume

Question 17

how should acetylcysteine be prescribed?

Answer 17

Dose calculated using actual body weight (max weight used is 110kg)

Diluent should be glucose 5% (sodium chloride if unsuitable)

Regimen given in 3 parts
- Part 1 given over 1 hour in 200ml of 5% glucose, 150mg/kg
- Part 2 given over 4 hours in 500ml of 5% glucose, 50mg/kg
- Part 3 given over 16 hours in 1 litre of 5% glucose, 100mg/kg

Question 18

how can you calculate the volume of a solution that is required?

Answer 18

Volume required = (dose prescribed x volume of solution) / amount of medicine in solution