How To Calculate Drug Dosages Using Age And Weight
The dosage of drugs prescribed is influenced by four main factors. They are:
1. The age of the person or patient
2. The body weight of the person or patient
3. The time taken for the drug to reach the circulating blood. This is affected by the route by which the drug is administered. Drugs given orally are absorbed more slowly and over a longer period of time than drugs given by the intramuscular route. A larger dose of the drugs is prescribed if it has to be given orally.
4. The rate at which the drug is destroyed or excreted by the body . This influences the size and frequency of the dose.
The dosage of drugs is recommended by the British Pharmacopoeia which shows two dosages:
1. The maximum which it is safe to give without producing signs of overdosage.
2. The minimum dose of a drug which is effective.
On some occasions, a medicine or lotion may be required in a strength not immediately available and the following guide may be of some help in calculations. However, the use of a part of a tablet, capsule or ampoule should be discouraged as it may result in over or under dosage. Pharmacies should provide drugs so that the unit dose supplied or multiple of that unit are used.
DOSAGE AND AGE
1. For less than 6 months old children, the fraction of adult dose for them is 1/20
2. 6-12 months old children gets the fraction of 1/15
3. 1-2 years receives the fraction of adult dose of 1/12
4. 2-3 years receives the fraction of adult dose of 1/8
5. 3-4 years gets the fraction of adult dose of 1/6
6. 4-6 years gets the fraction of adult dose of 1/4
7. 6-10 years gets the fraction of adult dose of 1/3
8. 10-13 years gets the fraction of adult dose of 5/12
9. 13-16 years gets a fraction of adult dose of 1/2
Insulin is dispensed in units. The label on the bottle indicates how many units there are in a millitre. It is well that the nurse should know that special syringes are used for the administration of insulin. They are marked in units instead of the ordinary marking in minims or millitres.