Stuck with Pre-Reg exam calculations?

[johnep]

Yes one is quite important!
johnep

[confused.com]

Mrs C is to be given zidovudine intavenously at a dose of 2mg/kg over 1 hour. What volume of sodium chloride 0.9% is necessary to produce a 2mg/ml infusion for this patient.
Patient weighs 63kg.

zidovudine is available as 200mg/20ml

a)12.6
b)25.2
c)50.4
d)63
e)239.47

[johnep]

Pt weighs 63kg, so dose at 2mg/kg is 126mg.

this is contained in 126/200 x 20 = 12.6ml.

Over one hour need to infuse 2mg/ml soln.

Therefore 63ml required of 2mg/ml to give total dose of 126mg

Therefore x + 12.6ml conc soln = 63ml

Therefore Xmls of saline required is 50.4mls.

Note figures given in question designed for easy calculation.
johnep

[emelianenko]

Hi

I am going to star Pharmacy this September. Since ive got some free time on my hands I thought I would go over some literature on Pharmacy calculations and put myself to the test lol

I flicked through some of the pre-reg questions and gave a few of those that made sense to me a shot and will post those later to get some feedback.

However this one I could do with some input on. The pharmacy I work at part time received a rx with similar kind of problem for the Pharmacist to tackle.

This Q is taken from the spring 2008 paper

Which one of the following is the correct weight of potassium
permanganate required to make 400 mL of a 1 in 8000 solution?
A 0.5 mg
B 2 mg
C 5 mg
D 20 mg
E 50 mg

Thanks in advance.

[admin]

The answer is E 50mg I think.

(1/8000) x 400 = 0.05g = 50mg

If it's wrong please let me know!

[emelianenko]

The answer is E 50mg I think.

(1/8000) x 400 = 0.05g = 50mg

If it's wrong please let me know!

lol i have no idea as to the right answer as i stated im going to be studying Pharmacy so was just curious as to the answer and thought process in tackling the above question. Maybe some of the others on this forum can verify what you have kindly shown

[kemzero]

The answer is E 50mg I think.

(1/8000) x 400 = 0.05g = 50mg

If it's wrong please let me know!

Me thinks ur spot on
it is correcto

[emelianenko]

Thanks Admin and Kemzero. Very much appreciated.

Okie, here are some more Q's i attempted from the 2008 paper. Would appreciate it if you guys could give me some feedback please

Question 31(Calc) concerns Benylin Dry Coughs (Original) which contains the
following:
Diphenhydramine hydrochloride 14 mg in 5 mL
L-menthol 2 mg in 5 mL
Dextromethorphan hydrobromide 6.5 mg in 5 mL
What weight of diphenhydramine hydrochloride is required to
prepare 150 litres of Benylin Dry Coughs (Original)?
A 42 g
B 195 g
C 420 g
D 1.95 kg
E 4.2 kg

2.8mg/1ml = X/150'000ml

2.8 x 150'000 / 1 = 420,000mg = 420 g

If a woman weighing 55 kg is given dobutamine by intravenous
infusion at a rate of 4.5 micrograms/kg/minute, how much
dobutamine will have been administered after 1 hour?
A 1.485 mg
B 7.425 mg
C 14.85 mg
D 74.25 mg
E 148.5 mg

4.5mcg/kg = X/55kg

4.5mcg x 55kg / 1 = 247.5mcg

247.5mcg x 60 = 14850mcg = 14.85mg

A patient with atrial fibrillation is started on amiodarone. The
medical practitioner prescribes the usual stabilising regime,
followed by the usual maintenance dose.
Given that other medication taken by the patient does not
interact with amiodarone, how many amiodarone 200 mg tablets
would you need to supply for the first 28 days of treatment?
A 28
B 49
C 56
D 63
E 84

For this Q I referred to the BNF.

1st week: 200mg tds = 3 x 7 = 21 tablets
2nd week: 200mg bd = 2 x 7 = 14 tablets
maintenance = 200mg od = 1 x 14 = 14

Sum = 49 tablets in total.

Directions for questions 38(Calc) and 39(Calc). For each numbered
question select from the list above it the one lettered option which is most
closely related to it. Within the group of questions each lettered option may be
used once, more than once, or not at all.
Questions 38(Calc) and 39(Calc) concern the following quantities:
A 0.2 micrograms
B 0.02 mg
C 0.2 mg
D 20 mg
E 200 mg

Select, from A to E, which one of the above:

38(Calc). is the most appropriate initial daily dose of alfacalcidol for a 5-
week-old child who weighs 4 kg to treat persistent
hypocalcaemia
39(Calc). is the weight of remifentanil that will be given to a 3-year-old
child weighing 16 kg over 25 minutes when given at a rate of
0.05 micrograms/kg/minute

Q38 (referred to BNF. states: CHILD under 20kg initially 50ng/kg daily)

50ng/1kg = X/4kg

50 x 4 / 1 = 200ng = 0.2mcg A

Q39

0.05mcg/kg = X/16kg
0.05 x 16/ 1 = 0.80

0.80mcg x 25 = 20mcg = 0.02mg B

[emelianenko]

Could someone help moi out on this Q please

If 400 mg of potassium permanganate is dissolved in 2.5 litres of water what is the percentage strength of the resulting solution?
A 0.008%
B 0.016%
C 0.032%
D 0.064%
E 0.08%

Thanks

[admin]

Could someone help moi out on this Q please


Thanks

400mg in 2.5L = 0.4g in 2500mls water

to know the % strength we need to know how many grams are in 100mls

(100/2500) x 0.4 = 0.016

so 0.016g in 100mls = 0.016% = B