Calculation of Dosage & Metric System

Kaleem ul Haq

Percentage Solutions• Percentage w/w express the number of grams

of active substance in 100g of solution .• Percentage w/v express the number of grams

of active substance in 100ml of solution.• Percentage v/w express the number of ml of

active substance in 100g of solution .• Percentage v/v express the number of ml of

active substance in 100ml of solution.

Percentage strength to millimoles Per Liter

• Let C=Percentage w/v strength of a salt.• W=milligrams of salt containing 1 millimole of

the specified ion• 100 milliliter of solution contain C grams of

salt• 1L of solution contain 10x C grams of

salt=10,000C milligrams • Millimoles per liter = 10,000C/w

Calculation of doses • We have following formulas for calculation of

doses • Young’s Formula• Dilling’s Formula• Cowling’s Formula• Fried’s Formula• Bastedo’s formula• Clark’s Formula• Gaubin’s formula

• Young’s Formula :-• Dose for Child = Age (years )/Age +12 x Adult

dose• This formula is used for children under 12 years

of age• Dilling’s Formula :-• Dose for Child = Age (years)/20 x adult dose• The fraction age/20 approx close to weight curve

between the ages 4 -20 so more than 10 years of age

• Cowling’s formula :-• Dose of child = Age (Years )+1/ 24 x Adult dose

• Fried’s formula :-• Dose of child = Age(months)/150 x Adult dose• Bastedo’s formula :- • Dose of child = Age (years )+3/30 x Adult dose• Clark’s formula :-• Dose of child = weight (pounds )/150 x Adult

dose

Gaubin’s formula Age(years) Dose for children with respect to adult

dose under 1 1/12

1-2 1/8

2-3 1/6

3-4 1/4

4-7 1/3

7-14 1/2

14-20 2/3

21- 60 full adult dose

60-70 4/5

70-80 3/4

over 90 1/2

Square Meter Surface Area Method• Child dose = Body Surface area of child x Adult dose Body Surface area of child• The average body surface area for an adult has been

given as 1.73meter square .

Reduction & Enlargement of Recipe • The following rules are used in converting the

recipe from one system to another• Rule 1 :-• To convert the recipe in imperial system to

metric system• Write grams in place of grains• Divide the minims by 1.1 and write result in

millimeters (for small scale )• Write grams in in place of ounce & milliliters

in place of fluidounce (for large scale)

• Rule 2 :-• To convert a recipe in metric system to

imperial system• Write grains in place of grams• Multiply the milliliter by 1.1 and write the

result in in minims (small scale )• Write ounce in place of grams & fluid ounce in

place of milliliters .

Calculation by Alligation

• Simple arithmetical method for calculation of resulting strength after mixing solutions or other substances .

Metric System

• The use of metric system of weights and measures was legalized in 1897 by the weights and measures (Metric System ) .

Length

• Basic unit = 1 meter (m)• 1 decimeter (dm) = 1/10th part of 1 meter • 1 centimeter (cm) = 1/100th part of 1 meter• 1 millimeter (mm) = 1/1000th part of 1 meter• 1 micrometer (um) = 1/1000th part of 1 cm• 1 nanometer (nm) = 1/1000th path of 1micron`

Mass• The international kilogram is the weight in

vacuum of platinum- iridium cylinder preserved at the international Bureau of Weights and Measurers

• Basic unit = 1 kilogram (kg)• 1 gram (g) = 1/1000th part of a kg • 1 milligram (mg) = 1/1000 part of a gram• 1 micrograms (ug) = 1/1000 part of milligram

Capacity

• The 1 Liter is the volume occupied by a cube with side of 1 decimeter

• Basic unit = 1 liter • 1 milliliter = 1/1000th part of a liter • 1 ml is equal to 1 cubic centimeter.