Calculation of Dosage & Metric System

Kaleem ul Haq

Raees Ajaib

Asad Mehmood

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.