Stuck with Pre-Reg exam calculations?

[Bulletproof]

Hey,

I'm stuck with some calc. qs. Would really appreciate the help!

1. In the TPN unit, you are required to prepare 60mmol of Potassium ions in 3.5 litres of TPN, 2 bags are required for the patient. Please calculate the total amount of Potassium 15% injection that is required.

a) 20mls
b) 30mls
c) 40mls
d) 50mls
e) 60mls



2. What weight of a drug Y, containing 20% w/w moisture, should be added when preparing a 20L batch of an aqueous solution formulation with a final concentration of 3% w/v anhydrous drug Y?


a) 250g
b) 500g
c) 750g
d) 1250g
e) 1500g

3) A doctor has asked you to predict the concentration of a drug with a half-life of 16 hours. On admission, the patient’s serum contains 84 micrograms/ml of the drug, could you please predict the plasma concentration at 24 hours?

a) 45
b) 41.5
c) 35
d) 33.5
e) 31.5

Also can you explain how you got the answers? I'm so confused about half life qs.

Cheers!

[shan]

Hey,

I'm stuck with some calc. qs. Would really appreciate the help!

1. In the TPN unit, you are required to prepare 60mmol of Potassium ions in 3.5 litres of TPN, 2 bags are required for the patient. Please calculate the total amount of Potassium 15% injection that is required.

a) 20mls
b) 30mls
c) 40mls
d) 50mls
e) 60mls

CHECK BNF : HOW MANYmmol OF POTTASSIUM IN 15% SOLUTION THEN THE ANSWER IS SIMPLE

2. What weight of a drug Y, containing 20% w/w moisture, should be added when preparing a 20L batch of an aqueous solution formulation with a final concentration of 3% w/v anhydrous drug Y?


a) 250g
b) 500g
c) 750g
d) 1250g
e) 1500g

Answr : 750G.20L= 20000 MLS. 100MLS WILL HAVE 3g, SO 20000MLS WILL HAVE 600g. NOW THE GIVEN POWDER HAS 20 % MOISTURE MEANING 100g POWDER HAS 80g OF ANHYDROUS DRUG SO TO GET 600g OF ANHYDROUS DRUG YOU NEED 600 x 100 / 80 = 750g.

3) A doctor has asked you to predict the concentration of a drug with a half-life of 16 hours. On admission, the patient’s serum contains 84 micrograms/ml of the drug, could you please predict the plasma concentration at 24 hours?

a) 45
b) 41.5
c) 35
d) 33.5
e) 31.5

Also can you explain how you got the answers? I'm so confused about half life qs.

SMPLE. HALF LIFE = AFTER A GIVEN PERIOD THE DRUG'S CONCENTRATION IS REDUCED BY HALF. SO IF HALF LIFE IS 16 Hrs THEN AFTER 16HRS THE DRUG IN THE BODY IS 84/2=42. NOW START WITH 42 AND YOU WILL SEE THAT AFTER 16Hrs THE CONC WILL BE 21. SO AFTER 8 HOURS IT WILL BE 21 + HALF OF 21 (10.5). hENCE THE ANSWER IS 24Hrs = 16 + 8 Hrs = 21 + 10.5 = 31.5

Cheers!

cHECK ALL THE RED BOLD LETTERS AS ANSWERS

[Bulletproof]

Thank you very much :-)

[Fleegle]

Threads such as this one seriously undermine my confidence in the presumed 'knowledge' of future pharmacists.

Fleeg.

[Nikolai]

Hey,

I'm stuck with some calc. qs. Would really appreciate the help!

Would have been good to see your ideas rather than relying on someone else to come up with the answers. It was very generous of Shan to give you asnwers AND explanations.