Stuck with Pre-Reg exam calculations?

[willerz86]

Yes, 24mcg/ml is correct.

[willerz86]

Here are some calcs to wet your appetite:

(1) 2. Assuming that digoxin tablets have a bioavailability of 0.6 and that crushing the tablet increases this to 1, what % dose increase would a patient experience if their 250mcg tablets were crushed to help them swallow?

A. 30%
B. 50%
C. 66%
D. 75%
E. 100%



If a 2g suppository mould requires 20mg active of a drug with a DV of 5, how much base will be required?

A. 1.960 g
B. 1.9 g
C. 2 g
D. 1.996 g
E. 1.99 g

Which of the following is an appropriate quantity of cream for the indication, duration and location stated:
1 30 g of topical steroid for 4 weeks for use on both hands for single daily application
2 200 mL of an emollient lotion for application to the scalp four times a day for 2 weeks
3 240 g of topical steroid for use on both arms for once daily application for 4 weeks

These are just a few of ones I had on a training day recently. Pretty good !

[johnep]

Last question may have something to do with 'Finger Tip Units'.?
johnep

[willerz86]

Could use finger tip units to calculate but much simpler to use the tables under topical corticosteroids and emollients section in BNF. Started on the Naplex calcs the other night, some are quite tricky !

[ghajini]

Assuming that digoxin tablets have a bioavailability of 0.6 and that crushing the tablet increases this to 1, what % dose increase would a patient experience if their 250mcg tablets were crushed to help them swallow?

A. 30%
B. 50%
C. 66%
D. 75%
E. 100%

Bioavailability is the amount of drug that reaches the systemic circulation
So if digoxin tablets have a bioavailability of 0.6 that means that 60% of the 250mcg of the tablet reaches the systemic circulation so 60/100 *250 = 150mcg. That basically means if a patient takes 250mcg tablet only 150mcg of the tablet will reach the systemic circulation.

If you crush the tablet and the bioavailbility is 1 that means 100% of the dose will reach the systemic circulation. That means all of the 250mcg tablet will reach systemic circulation.

Therefore the difframce between 150 and 250 is a 100 so 100/150*100 = 66% dose increase. So i would say answear C.


If a 2g suppository mould requires 20mg active of a drug with a DV of 5, how much base will be required?

A. 1.960 g
B. 1.9 g
C. 2 g
D. 1.996 g
E. 1.99 g

Suppository mould is 2g that means you need 2g of base
Drug required is 20mg = to 0.02g
0.02/5 = 0.004g
That basically means that 0.02g of drug will displace 0.004g of drug.
2-0.004 = 1.996
So i would say anwear d

If you look at page 689 of bnf 60
States the suitable quantities of dermatological preps to be prescribed for specific arears of the body

Which of the following is an appropriate quantity of cream for the indication, duration and location stated:
1 30 g of topical steroid for 4 weeks for use on both hands for single daily application
Recommended is 25-50g so i would say true

2 200 mL of an emollient lotion for application to the scalp four times a day for 2 weeks
200ml so i would say true

3 240 g of topical steroid for use on both arms for once daily application for 4 weeks

100-200 so i would say false

So the first and second statements are true.

Thats the way i would work out the answears but not sure if they are correct.

[Asterix]

0. A patient is admitted into hospital following a drug overdose. On admission a plasma concentration of 64 micrograms/ml is measured. Given that the half-life of the drug is 16 hours, what would you except the approximate plasma concentration to be after 24 hours? (You may assume that the elimination is described by a 1st order process.)


A 2 micrograms/ml

B 4 micrograms/ml

C 16 micrograms/ml

D 24 micrograms/ml

E 48 micrograms/ml


Can use common sense to work out 24mcg/ml but is there an eq you could use for this question (cross multiplication of some sort?)

[ghajini]

Hi

I get the answear 16mcg/ml

If the current plasma concentration is 64mcg/ml and half life is 16 hours then after 16 hours the concentration will be 32mcg/ml. Then at 24hrs it will half to 16mcg/ml. Therefore i would go for answear c because i thought the concentration falls by half at each half life. Could you please explain how you got 24mcg/ml as your answear.

[willerz86]

Hi

I get the answear 16mcg/ml

If the current plasma concentration is 64mcg/ml and half life is 16 hours then after 16 hours the concentration will be 32mcg/ml. Then at 24hrs it will half to 16mcg/ml. Therefore i would go for answear c because i thought the concentration falls by half at each half life. Could you please explain how you got 24mcg/ml as your answear.

Read the question again, I think you will find the plasma concentration will be 16mcg/ml at 32 hours, not 24.

[minisini]

You start out with 64, in 16 hours it will be 32. In 32 hours it will be 16. So the answer has to be between 16 and 32. So it must be 24.

[Asterix]

You start out with 64, in 16 hours it will be 32. In 32 hours it will be 16. So the answer has to be between 16 and 32. So it must be 24.

Sorry I meant 16.

I worked it out as the same other said, but say the answers were 16,17,18 would there be a definite way of working out the correct conc?