Question

Doctor’s Order: Streptomycin 1.75 mg/ lb IM q 12 hr; Available: Streptomycin 0.35 g / 2.3 mL. How many mL will you administer a day to a 59 Kg patient?

Could you please do this problem using dimensional analysis? I just need one example to see how it's done. Thank you!

Answer 1

To solve the above calculation the following formula is used.

Desired dose/ Amount in hand x quantity.

Here the weight of the patient is 59 kg which should be converted into lb as the Doctor's order is 1.75mg/lb

= 59 x 2.2

wt = 129.8 lb = 130 lb

Desired dose is per lb, dose should be calculated per kg

Desired dose = 1.75mg /lb

= 1.75 x 130

= 227.5mg/kg per dose

Desired dose / Amount in hand x quantity

= 227.5 mg/0.35 g x 2.3ml

Here the amount in hand is 0.35g which should be converted into mg as the Desired dose is in mg.

= 0.35g* 1000

= 350 mg

= 227.5 mg / 350mg x 2.3 ml

= 0.65*2.3

= 1.49 =1.5 ml per dose.

The ml per dose of the IM injection given to the patient is 1.5ml

The ml per day given to the patient is 3 ml per day given in two doses.