Pre-reg june 2011 exam

[cheesecake]

Hi guys,

Can someone please help me with the following questions ( im taking the exam in sept)

1) Mr F currently takes Hydrocortisone tablets 130mg daily. His doctor wants to change him onto an equivalent ant-inflammatory dose of dexamethasone tablets. Which one of the following is the most appropriate dose of dexamethasone tablets for the doctor to prescribe?
A)2.5mg
B)5mg
c)6.5mg
d)7.5mg
e)8mg


2)You have been asked to dilute Cutivate(R)cream in the following proportion 1:4 to make 300g of the final product.

Statement One
The amount of the Cutivate(R)cream this requires is 60g.

Statement two
The formula for calculating amount is one part of Cutivate(R)cream to be added to four parts diluent.

[CJH86]

1) There is a steroid equivalency table in the BNF corticosteroid section, 20mg of hydrocortisone is equivalent to .75mg of dexamethasone....so that should equate to just below 5mg.

2) statements are true as it would be 60g:240g = 300 as 1 part to 4 parts diluent

[canaria]

first question:
from the bnf, 20mg hydrocortisone is equivalent to 750 microgram of dexamethasone
pt. takes 130mg hdrocortisone so the equivalent in dexamethasone= 130/20*0.75mg=4.875mg. the closest answer is B

second question:

the dilution factor is one part of the cream and 4 parts of the diluent and the total amount is 300g.

from the cream we need to take 1 part
total number of parts=1+4=5
therefore 1 part=300/5=60grams so the first statement is true

diluent 300-60=240 g which is 4 times the cream, so we need to add 60 gram of the cream to 240 gram diluent in order to make 300 g of the diluted cutivate cream.
so the statement is true and both statements are linked so the answer would be A.

this curavate diluted 1:4 is as the same as Betnovate cream and Betnovate RD cream (0.1% and 0.025% betamethasone valerate respectively).

hope it helps

[cheesecake]

thanks guys.

I have another one!

What weight of drug X, containing 10%w/w moisture, should be added when preparing a 20L batch of an aqueous solution formulation with a final concentration of 2%w/v of anyhydrous drug?

Answer is: 444.4g

[canaria]

amount of anhydrous drug = 2/100*20000= 400 gram.
the drug contains 10% moisture
that means the amount of anhydrous is 90% of the drug.

the amount of the drug=400*100/90=444.4 gram.

another solution:

2%= 20g per litre= 400 per 20 litre
400*100/90=444.4
cheers

[cheesecake]

So how did you guys find the exam last friday? what did people make of the calculations??

[Asterix]

The burns one said something like pt has a BSA of whatever and has 30% burns and you needed to calculate the total size of dressing required for daily application for a week.

how can you do this for someone who is 1.7m2 for example. Do you convert into kg and height?!