This document discusses posology, which is the science of determining safe and effective drug dosages. It outlines several key factors that influence drug dosing, including age, weight, gender, severity of disease, health/nutrition status, pathological states, tolerance, route of administration, time between doses, idiosyncrasies, allergies, and interactions between multiple drugs administered simultaneously. Several formulas are presented for calculating dosages for children of different ages based on an adult dose, including Young's, Dilling's, Fried's, Clark's, Cowling's, and Bastedo's formulas. The goal of posology is to determine the optimal therapeutic dose with the lowest risk of adverse effects.

1. J.S.SINGH INSTITUTE OF PHARMACY
TOPIC: POSOLOGY
Mr. Ramnivas
Assistant professor
M.PHARM ( PHARMACETICS)

2. POSOLOGY
Posology (posos means, how much and logos mean, science)
is a branch of medical science which deals with dosage or
quantity of drug, which can be administered to produce the
required pharmacological action.
Dose. Dose is a quantity of drug which can be used to
produce the optimum therapeutic effect in a particular with
a lowest possible amount.
Factor affecting dose and action of drugs
1.Age and weight of patient. In general children require
smaller dose than adults. Either Young’s formula (based on
age) or Clark’s formula (based on weight) can be used for
calculation of doses.

3. 2.Gender/sex. This is particularly important in case of
treatment of sex hormones. Female adults generally require
smaller dose than males due to presence of more fat.
3.Severtity of disease. It is a common experience that dull
headache may necessitate administration of 2-3 tablets of
same drug, but this is true in all cases
4.Health and nutrition. Debilitated and anemic patient are in
general ,more sensitive to toxic effect of drug and they are
given in smaller doses. Person with severe anemia
associated with hookworm infestation are more susceptible
to the toxic effect of Tetrachloroethylene

4. 5.Pathological state: If the organs, through which
biotransformation or excretion take place, are diseased then
smaller dose is indicated. For example: in case of renal
insufficiency, phenobarbitone ( mainly excreted by kidney)
should be given in smaller dose.
6.Tolerance: some children can tolerates comparatively large dose
of arsenic, belladonna and calomel. Tolerance can be acquired as
a result of repeated administration of some drugs e.g morphine ,
heroin and cocaine.
7. Route of administration: in general the rapidity of drug decrease
with route of administration in following order
Intravenous intramuscular subcutaneous oral

5. 8. Time and frequency of drug administration: biological half
life of a drug i.e the time required for the blood level of drop
down to 50% of the initial peak level, is the main factor
governing frequency of drug administration.
9. Idiosyncrasy: morphine may produce excitation in some
individuals, specially women, although normally it depress
central nervous system.
10. Allergy: penicillin may produce anaphylactic shock (sudden
fall of blood pressure) in allergic patients but not in normal
patients.

6. 11. Simultaneous administration of two or more drug:
a. Additive : when two or more drug given together produce the
some effect, e.g. Carbachol, and acetylcholine.
b. Synergism: synergism, the effect produced is greater than the
algebraic sum of the individual effects e.g. Adrenaline and
cocaine.
c. Antagonism: when two drug have opposite effect e.g.
ephedrine and Phenobarbital.

7. Calculation of dosage for dosage
a. According to age
(i) young’s formula
child dose = age in year adult dose
age in year +12
This formula is used for calculation of dose for children under
12 year
(ii) Dilling’s formula
Child dose = age in year adult dose
20
This formula is used for calculating the dose of children in
b/w 4 to 20 years

8. (iii) Fried’s formula
child dose = age ( m0nth) adult dose
150
This formula is used to calculate the dose for infants up to 8 years
B. According to weight
(i) Clark’s formula
child dose = child weight adult dose
70

9. C Dose calculation for any age group size:
(i) Cowling’s formula.
Child dose= age in year + 1 adult dose
24
(ii) Bastedo’s formula.
Child dose= age in year + 3 adult dose
30

10. THANK YOU