Why is the dosage of all drugs same for every individual?

Q: While giving medicines, how is that the dosage remains same for each human being? Each individual has different metabolisims, thought pattern, living conditions, weight measures etc. Is it a general feeling amongst pharma companies that a set of dosage or mg of each ingredients are sufficent for each human being?

A:Before a drug is introduced, it passes through elaborate and extensive testing in both healthy volunteers and patients at various dosage levels to determine the right dose. Generally the dosage of most medicines is per kg of body-wt basis. However, minor differences in weight are not clinically important.