Calculation of Doses

Lecture Four
Calculation of Doses
Dose
The dose of a drug is the quantitative amount administered or taken by a patient for the intended medicinal effect.
The dose may be expressed as a single dose (the amount taken at one time), a daily dose, or a total dose (the amount taken during the course of therapy).
A daily dose may be subdivided and taken in divided doses, two or more times per day depending on the characteristics of the drug and the illness. The schedule of dosing (e.g., four times per day for 10 days) is referred to as the dosage regimen.

Number of doses = Total quantity / Size of dose
The usual adult dose of a drug is the amount that ordinarily produces the medicinal effect intended in the adult patient.
The usual pediatric dose is similarly defined for the infant or child patient.
Many anticancer drugs are administered cyclically, usually for 21 to 28 days, with arrest period between dosing cycles to allow recovery from the toxic effects of the drugs.
The median effective dose of a drug is the amount that produces the desired intensity of effect in 50 % of the individuals tested.
The median toxic dose of a drug is the amount that produces toxic effects in 50 % of the individuals tested.













Dose Measurement
Teaspoon and Tablespoon
Pharmacists and physicians accept a capacity of 5 mL for the teaspoonful and 15 mL for the tablespoonful. It should be noted that the capacities of household teaspoons may vary from 3 to 7 mL and those of tablespoons may vary from 15 to 22 mL.
1 teaspoonful (tsp.) ? 1?6 fluidounce ? 5 mL
1 tablespoonful (tbsp.) ? 1?2 fluidounce ? 15mL

The Drop as a Unit of measure
The United States Pharmacopeia defines the official medicine dropper as being constricted at the delivery end to around opening with an external diameter of about 3 mm. The dropper, when held vertically, delivers water in drops, each of which weighs between 45 and 55 mg. accordingly, the official dropper is calibrated to deliver approximately 20 drops of water per milliliter (i.e., 1mL of water ?1 gram or 1000 mg / 50 mg /drop = 20 drops).