1. Calculation of Doses I
Dr. Osama A. A. Ahmed

2. Dose Definitions
Dose of a drug: the quantitative amount administered or taken by a patient for the intended medicinal effect
Single dose: the amount taken at one time
Total dose (Daily dose) : the amount taken during the course of therapy (may be subdivided in divided doses)
Dosage regimen: the schedule of dosing (4 times per day for 10 days)
Dr. Osama A. A. Ahmed

3. Dose Definitions
Usual adult dose: the amount that ordinarily produces the medicinal effect intended in the adult patient
Usual pediatric dose: : the amount that ordinarily produces the medicinal effect intended in the infant or child patient
Usual dosage range : the quantitative range or amounts of the drug that may be prescribed within the guidelines of usual medical practice
Median effective dose: the amount that produces the desired intensity or effect in 50% of the individuals tested.
Minimum effective concentration:
the minimum concentration determined
that can be expected to produce the drug’s
desired effects in a patient.
Minimum toxic concentration:
The base level of blood serum concentration that produces dose-related toxic effects.
MTC
MEC
Average serum conc. (mg/ml)
Time after drug administration (hours)
Dr. Osama A. A. Ahmed

4. Household measure (Abbreviation)
Dose Measurement
Doses are measured and administered by professional and paraprofessional personnel in case of institutional setting.
adults or child’s parents are generally measures and administers medication in the home setting.
Household measures
Household measure (Abbreviation)
ounce
Metric system
1 teaspoonful (tsp)
1 tablespoonful (tbsp)
1/6 fluidounce
1/2 fluidounce
5 ml
15 ml f
f ss
Dr. Osama A. A. Ahmed

5. Dose Measurement Household measures Calibrated droppers
US Pharmacopeia, official medicinal dropper held vertically delivers approximately 20 drops water per millilitre.
A drop (abbreviated gtt) doesn’t represent a definite quantity (few liquids have the same surface and flow characteristics as water).
Signa
Label
dose
f i
One teaspoonful
5 ml
f ii
One dessertspoonful
10 ml
f ss
One tablespoonful
15 ml f
One coffee cupful 30 m
One drop
Dr. Osama A. A. Ahmed

6. Dose Measurement Case 1 Answer 30 mg dextromethorphan HBr 15 ml
A physician asks a pharmacist to calculate the dose of a cough syrup so that it may be safely administered dropwise to a child. The cough syrup contains the active ingredient dextromethorphan HBr, 30 mg/15 ml, in a 120- ml bottle. Based on the child’s weight and literature references, the pharmacist determines the dose of dextromethorphan HBr to be 1.5 mg for the child.
The medicine dropper to be dispensed with the medication is calibrated by the pharmacist and shown to deliver 20 drops of the cough syrup per 1 ml.
Calculate the dose in drops, for the child.
Answer
30 mg dextromethorphan HBr ml
1.5 mg dextromethorphan HBr X ml
X = 15 * 1.5/30 = 0.75 ml
Number of drops of cough syrup in 0.75 ml dose
1 ml drops of cough syrup
0.75 ml X drops of cough syrup
X = 0.75 * 20/1 = 15 drops of cough syrup
Dr. Osama A. A. Ahmed

7. Calculation of doses Patient Parameters
Geriatric medicine or geriatrics: is the field that encompasses the management of illness in the elderly
Pediatrics: is the branch of medicine that deals with disease in children from birth through adolescence.
Neonate (newborn): from birth to 1 month, neonate is considered premature if born less than 37 weeks‘ gestation
Infant: 1 month to 1 year
Early childhood: 1 year through 5 years
Late childhood: 6 years through 12 years
Adolescence: 13 years through 17 years of age
Dr. Osama A. A. Ahmed

8. Calculation of doses Patient Parameters According to age
Child and infant doses
Young’s rule
Cowling’s rule
Fried’s rule for infants
Dr. Osama A. A. Ahmed

9. Calculation of doses Patient Parameters According to body weight
Clark’s rule
According to body surface area (BSA)
To determine patient’s BSA, use standard Nomogram or this equation
Dr. Osama A. A. Ahmed

10. Calculation of doses
If the adult dose of phenobarbital is 15 mg, what will be the dose for an 8 year-old child?
Young’s rule
= (8/8+12)X 15 = 6 mg
Cowling’s rule
= (9/24)X 15 = 5.625
Dr. Osama A. A. Ahmed