DOSE CALCULATIONS.
1.Calculating quantities needed to prescribe:
Tablets or capsules: This is fairly straightforward as you know how many tablets the patient
needs to take and how long you need to give them. It can get more tricky however with
variable dosage. Here are 2 examples of more complicated dosage quantity calculations:
1. A patient with brittle asthma requires a reducing course of prednisolone back to
maintenance dose of 5mg following an acute exacerbation. You prescribe the following
regimen, calculate how many prednisolone 5mg tablets are required to get back to
maintenance dose.
40mg daily for 5 days then
30mg daily for 5 days
25mg daily for 3 days
20mg daily for 3 days
15mg daily for 2 days
10mg daily for 2 days
then 5mg maintenance as before
2. A patient is on warfarin for atrial fibrillation. You prescribe a new dosage regimen based on their
latest INR result: Take 4mg daily Mon-Fri and 5mg daily Sat/Sun. Warfarin comes as 1mg, 3mg and
5mg tablets. Calculate the quantity you would need for a 28-day supply.
Inhalers and sprays: You would need to know how many dosage units are in each inhaler or spray and
know the strength of the dosage unit, the frequency and duration of treatment.
3. A patient requires 200 dose beclometasone nasal spray 50 micrograms for hay fever. The dose is 2
sprays in each nostril twice a day, how long should the spray last?
4. How long will the eye drops for glaucoma in the following prescription last?
Bimatoprost ophthalmic solution
1 drop once daily in both eyes at night
Supply 5ml
Answers
1 = 107
