Shelf-life calculations! Need a step-by-step answer, please! 1. An antibiotic ha

Question

Shelf-life calculations! Need a step-by-step answer, please!

1. An antibiotic has a shelf life of 120 hours when refrigerated (50C). If a patient stores the solution at (300C) at home. What will be the shelf life of the solution:

2. What will be the new shelf life of a compounded preparation that is normally stored at (200C) with an expiration date of four week, if it is stored in the refrigerator (50C)?

3. Doctor Martins received a prescription for an ophthalmic solution with a shelf-life of 50 hours at room temperature (250C). He left the prescription in his car to attend classes. The temperature on that summer day rose to 400C. How long will the solution remain good for use?

4. A prescription is received for an ophthalmic solution with a shelf life of 3 hours at room temperature (250C). The preparation is to be administered in a physician

Explanation / Answer

For every rise in 10 deg C (18 deg F) the rate is halved.

This can be mathematically shown as

R2 = R1*2^((T1-T2)/10)

1.

R2 = 120*2^((5-30)/10)

= 120*2^(-2.5)

= 21.21 hrs

2.

R2 = 4*2^((20-5)/10) = 4*2^(1.5) = 11.31 weeks

3.

R2 = 50*2^((25-40)/10) = 50*2^(-1.5) = 17.68 hrs

4.

let refrigerator be 5 deg C

R2 = 3*2^((25-5)/10) = 3*2^2 = 12 hrs

Since the drug when refrigerated has only 12 hrs of shelf life. It cannot be prepared the evening before because it will lose its potency.

5.

the potency will be decreased to half(22 hrs) when the temperature rises from 20 C to 30 C.

after 12 hrs it will still have a potency of 10 hrs.

(10/22)*100 = 45.45 % of original potency.

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