Question

A child who weighs 37 lb is prescribed 5 mg/kg/day of mediation X to be taken “4 times a day”. X is available as a syrup of concentration 12.5 mg/5 mL.

(a) Assuming that “4 times a day” means equal doses every 6 hours, what should be the volume of syrup for each dose?

(b) Naturally, it would be easier for the child to take the dosage as an integral number of 5ml teaspoonfuls. How would you prepare the total volume required for 30 days’ dosage using “X-diluent” to appropriately dilute the syrup? How many 5 mL teaspoons of your diluted solution would the child take at each 6-hourly dose?

1 kg = 2.205 lb

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need part (b) only!

Answer 1

(a)

Convert pounds to Kg

37 x 2.205 = 16.78 Kg

1 kg requires 5 mg

So 16.78 Kg requires 16.78 Kg/1 x 5mg = 83.9 mg/day

Now divide 83.9 mg into 4 doses

83.9 mg/4 = 20.98 mg/doze

Calculate the volume of syrup which contain 20.98 mg

12.5 mg in 5 ml

So, 20.98 mg in 20.98 mg/12.5 mg x 5 = 8.392 ml

= 8.4 ml

(b) It is easy to take the dosage as an integral number of 5ml teaspoonfuls

Step 1 Calculate the volume of syrup for 30 days, if child take 10 ml (2 teaspoonfuls)

Each dose 10 ml

4 dose = 4 x 10 ml = 40 ml

Total volume of syrup for 30 day will be 30 x 40 ml = 1200 ml

Step 2 Calculate the volume of syrup for 30 days, if child take 8.4 ml dose 4 times with known concentration 12.5 mg /5ml

30 x (4 x 8.4) = 1008 ml

Step 3

Calculate the volume of X-diluent

1200ml – 1008 ml = 192 ml

Step 4

We would take 1008 ml of syrup of known concentration (12.5 mg /5ml) in1.5L liter volumetric flask and dilute it by adding 192 ml distil water.

Now the concentration of the syrup will be 10.5mg/5ml

(1008 x 12.5 mg/5 mL = 1200 x M₂

M₂ = 10.5mg/5ml)

2 teaspoons of diluted solution would the child take at each 6-hourly dose.