Nematodes

Pharmaceutical calculations

1. Prepare 100 ml, 2.5% solution (desired volume and %age) from 4% (available %age) solution.

Formula

                               % age  desired
Vol. required =    ----------------------    X    Vol. desired
                               % age available

Solution

                            2.5
Vol required =   ------- X 100
                             4
   Vol required = 62.5 ml
Volume of solvent or vehicle  =  100  -  62.5   =  37.5 ml
Where 62.5 ml is the volume of available solution that we mix with 37.5 ml water in order to make 100 ml of solution.

2. Prepare 500 ml, 5 % drug solution from 10 % stock solution.

Solution

                            5
Vol required =   ------- X 500
                           10
 Vol required  = 250 ml of drug stock solution.
We mix 250 ml of stock solution with 250 ml of water (solvent) in order to make 500 ml of 5% drug solution.

3. Prepare 500 ml, 70% solution from 50% and 95% solutions.

Solution

Note: Subtract 70 (% age of the desired solution) from each stock solution %age and write under the opposite stock solutions values.

            50%                                    95%
         -----------------------------------------
            25                                        20                   (we divide both values with the common no. i.e., 5)
            5                                           4
Proportion sum   =    5 + 4  =  9
                                                                      5
Vol. required from 50% stock solution =  -------   X  500
                                                                       9

Vol. required from 50% stock solution = 277.5 ml

                                                                      4
Vol. required from 95% stock solution =  -------   X  500
                                                                       9
Vol. required from 95% stock solution   =   222.5 ml
 Total volume =  277.5   +   222.5
 Total volume = 500 ml

4. Prepare 100 ml, 60% solution from 80% and 50% stock solutions.

Solution

              50%                                   80%
            -----------------------------------------
              20                                       10    (we divide both values with the common no. i.e., 2)
              10                                        5     (we divide both values with the common no. i.e., 5)
               2                                         1
Proportion sum = 2 + 1
                          =   3
                                                                       2
Vol. required from 50% stock solution =  -------   X 100
                                                                      3
                                                               = 66.66 ml
                                                                      1
Vol. required from 80% stock solution =  -------   X  100
                                                                      3
                                                               =   33.33 ml
Total volume = 66.66 ml  + 33.33 ml
                      =  100 ml

5. How many ml of 5% solution of a drug will be required for a dog weighing 10    kg? While the recommended dose is 20 mg per kg bodyweight.

Formula

                      Bodyweight
        Dose = ---------------------  X Dose rate
                      Conc. of a drug
Note: If the conc. is in %age then multiply that %age with 10

Solution

                         10 kg
      Dose =    -------------  X  20 mg/ml
                      50 mg/ml                 ( 5 X 10 = 50 )
               = 4 ml    (solution of a drug is required)

 6. A cat weighs 9 lbs and requires a drug dose rate of 0.5 mg per kg, and the conc. of the drug solution is 1%. Find the dose rate?

Solution

1 kg = 2.2 lbs
Weight of the cat in kg = 9 / 2.2  = 4.09 kg

Dose  =  4.09 X 0.5 / 10 = 0.2 ml 

7. Preparation of serial dilution